A111D3 0731^1 lililli"

NBS SPECIAL PUBLICATION 584

U.S. DEPARTMENT OF COMMERCE / National Bureau of Standards

oint Conference on Measurements and

Standards for Recycled Oil/Systems

Performance and Durability
NATIONAL BUREAU OF STANDARDS

The National Bureau of Standards' was established by an act of Congress on March 3, 1901. The Bureau's overall goal is to strengthen and advance the Nation's science and technology and facilitate their effective application for public benefit. To this end, the Bureau conducts

research and provides: (1) a basis for the Nation's physical measurement system, (2) scientific and technological services for industry and government, (3) a technical basis for equity in trade, and (4) technical services to promote public safety. The Bureau's technical work is per- formed by the National Measurement Laboratory, the National Engineering Laboratory, and

the Institute for Computer Sciences and Technology. THE NATIONAL MEASUREMENT LABORATORY provides the national system of

physical and chemical and materials measurement; coordinates the system with measurement

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'Headquarters and Laboratories at Gaithersburg, MD, unless otherwise noted; mailing address Washington. DC 20234.

-'Some divisions within the center are located at Boulder, CO 80303.
Joint Conference on Measurements and Standards for Recycled Oil/Systems Performance and Durability

lArtr* Ml JLl m

Proceedings of a Conference held at the National Bureau of Standards, PEC 1 5 1980 Gaithersburg, MD, October 23-26, 1979

Donald A. Becker, Editor

Office of Recycled Materials National Measurement Laboratory

National Bureau of Standards Washington, DC 20234

Sponsored by: Recycled Oil Program

National Bureau of Standards

U.S. Department of Commerce ASTM Technical Division P. on Recycled Petroleum Products Mechanical Failures Prevention Group (MFPG)

Center for Materials Science. NBS

Office of Naval Research Department of Energy NASA Goddard Space Flight Center Naval Air Systems Command

U.S. DEPARTMENT OF COMMERCE, Philip M. Klutznick, Secretary

Luther H. Hodges, Jr., Deputy Secretary Jordan J. Baruch, Assistant Secretary for Productivity, Technology and Innovation NATIONAL BUREAU OF STANDARDS, Ernest Ambler, Director Issued November 1980
Library of Congress Catalog Card Number: 80-600159

National Bureau of Standards Special Publication 584

Nat. Bur. Stand. (U.S.), Spec. Publ. 584, 334 pages (Nov. 1980) CODEN: XNBSAV

U.S. GOVERNMENT PRINTING OFFICE WASHINGTON: 1980 For sale by the Superintendent of Documents, U.S. Government Printing Office, Washington, D.C. 20402

Price $8.00 (Add 25 percent for other than U.S. mailing)
PREFACE

On December 22, 1975, President Ford signed into law an act passed by the Congress of the United States entitled "The Energy Policy and Conservation Act of 1975" (Public Law 94-163). Section 383 of this act states that the National Bureau of Standards (NBS) shall develop test procedures "...for the determination of substantial equivalency of re-refined or otherwise processed used oil... with new oil for a particular end use." Further, NBS is to "...report

such procedures to the [Federal Trade] Commission..." as soon as practicable. This NBS conference, held on October 23 through 26, 1979, is part of the continuing NBS response to this legislation. This conference had a number of important objectives, including the following: 1) to obtain information and input to the NBS Recycled Oil Program from all relevant sources; 2) to report to you on the directions and progress being made towards the more effective re-use

and utilization of our used petroleum resources; 3) to discuss the importance of used oil analysis in the performance of lubricating oil systems; and 4) to bring together in one place all of the different people involved with lubricating oils and their more effective

utilization. From comments received during and after the conference, these objectives were

achieved. Certain commercial materials and equipment are identified in this proceedings in order to specify adequately the experimental procedure. In no case does such identification

imply recommendation or endorsement by the National Bureau of Standards, nor does it neces- sarily imply that the material or equipment identified is necessarily the best available for

the purpose. There were a total of 178 registrants at this meeting, with a breakdown as follows: 58 Government representatives (Federal Trade Commission, Department of Energy, NASA, Department

of Defense, NBS, and seven States plus Puerto Rico and the province of Ontario, as well as representatives from the Canadian and West German Federal Governments); 101 representatives

from private industries (engine manufacturers--8, virgin petroleum refiners and additive manufacturers—40, used oil re-refiners and recyclers--32 (including oil recyclers from

Canada, West Germany, France, England and India), and other industry—21); and 19 attendees

who were consultants or who represented consulting firms, testing laboratories, universities,

or nonprofit organizations. Of the registrants described above, the foreign visitors total 24 with 13 from Canada, six from West Germany, two from England, and one each from France,

India and the Netherlands.

It was felt that the conference participants again made a very important contribution to the available knowledge and understanding of the problems and opportunities in oil recycling

and used oil analysis and evaluation. We plan to hold another conference on the testing and evaluation of recycled lubricating oil in the fall of 1981.

Donald A. Becker, Manager

Recycled Oil Program

ABSTRACT

This publication is a formal report of the Joint Conference on Measurements and Standards

for Recycled Oil /Systems Performance and Durability held at the National Bureau of Standards

on October 23 through 26, 1979. There were seven sessions on specific subject areas, with a total of 32 technical presentations. The subject areas were as follows: (I) Recent Developments in Recycled Oil, (II) Engine Oil Evaluation, (III) Lube Oil Base Stock Characterization,

(IV) Oil Analysis for Engine Condition Monitoring, (V) Bench Tests for Oil Evaluation - I, (VI) Bench Tests for Oil Evaluation - II, and (VII) Systems Performance and Durability.

Included in this report are the entire texts of the various presentations, including figures

and tables. Keywords: Engine oil; hydraulic oil; industrial oil; lubricating oil; oil specifications;

petroleum standards; petroleum test methods; recycled oil; re-refined oil; used oil; waste oil.

v

CONTENTS

Page OVERVIEW

Opening Remarks 3

E. Ambler

General Comments 5

P. Strigner

Brief Overview of the NBS Office of Recycled Materials (ORM) 7

H. Yakowitz Conference Objectives 9

D. Becker, Recycled Oil

A. W. Ruff, MFPG Session 1. RECENT DEVELOPMENTS IN RECYCLED OIL Activities of the National Association of Oil Recovery Coordinates 15

D. Eastep

The Maryland Oil Recycling Legislation 17

C. Wiley and D. Phillips

Re- refining Oil in India 25

M. Bhargava

Re-refining Waste Oils: Improving Acid/Clay Treatment by Using Acid Sludges

as an Additional Fuel in Cement Kilns 35

A. Roll in and L. Estaque

Session 2. ENGINE OIL EVALUATION

Status of the MIL-L-46152A Engine Oil Specification 51

T. Bowen

Field Test of Re-refined Automobile Engine Oil in RCMP Vehicles 55

J. Armstrong

PROP Re-refined Oil Engine Test Performance 69

R. Linnard

Historical Perspective of Lubricant Deposit Evaluations at Southwest Research Institute 75

J. Bowden and S. J. Lestz Current Activities of the National Bureau of Standards Recycled Oil Program . . 97

D. Becker Session 3. LUBE OIL BASE STOCK CHARACTERIZATION

ASTM/NBS Base Stock Consistency Study 105

K. Frassa Properties of Canadian Re-refined Base Oils 109

P. Strigner Association of Petroleum Re-refiners Standards for Re-refined Base Oils .... 123

R. Pedal 1

vi i
The Viscometric Requirements for Re-refined Engine Oils 127

T. Selby Comments From a Producer of Virgin Base Oil 139

D. Espey Characterization of Lubricating Base Stocks for Automotive Crankcase Oils . . . 141

S. Hsu Session 4. OIL ANALYSIS FOR ENGINE CONDITION MONITORING

Wear Particle Equilibrium Measurements and Their Significance 159

R. D. Driver and E. R. Bowen Used Oil Analysis: Past, Present, and Future 167

C. Schwarz Wear Particle Analysis from Grease-Lubricated Bearings 173

W. Rosenlieb

Engine Condition Defined by Oil Analysis 183

C. Salvesen Session 5. BENCH TESTS FOR OIL EVALUATION - I. Engine Oil Evaluation Through Bench Testing 191

S. Hsu Development of the Army Thermal Oxi dation Lube Oil Tester 205

M. Valtierra and S. Lestz Predictive Test Method for Coking and Fouling Tendency of Used Lubricating Oil 221

G. Steele, D. Brinkman, and M. Whisman Antioxidant Consumption and Oxidative Degradation of Lubricants 227

S. Korcek, L. Mahoney, M. Johnson, and K. Otto Application of the Antioxidant Capacity Test to Re-refined and Virgin Base Stock Oils .237

R. Rebbert Session 6. BENCH TESTS FOR OIL EVALUATION - II. Pin-and-V-Block and Ring-and-Block Bench Wear Tests for Engine Oil Evaluation 245

L. Ives and P. Boyer

The Four-Ball Wear Test for Engine Oil Evaluation 261

R. Gates and S. Hsu Application of Differential Scanning Calorimetry to the Characterization

of Lube Oils 271

J. Walker and W. Tsang Evaluation of Basestock and Formulated Lubes Using the Penn State Microoxidation Test 285

E. Klaus, V. Krishnamachar, and H. Dang Determination of Polychlorinated Biphenyls in Waste and Lubricating Oils 295

S. Chesler, W. May, P. White, R. Parris, and F. Guenther

viii
Session 7. SYSTEM PERFORMANCE AND DURABILITY

Lubricant Factors in Rolling Contact Fatigue 301

C. Rowe The Relationship Between Viscometric Laboratory Measurements and Field Performance and Service 313

T. Selby System Health Monitoring Through Wear Particle Analysis 329

P. Senholzi Mechanical Failures and Lubrication Performance 339

M. Peterson

LIST OF ATTENDEES 347

OVERVIEW

1

OPENING REMARKS Good morning, and welcome to NBS. I am very pleased that this, the Third Recycled Oil Conference, is co-sponsored by NBS, ASTM, and the Mechanical Failures Prevention Group. This cooperation demonstrates substantial interaction between various segments of industry, government, and academia. Together, we can make headway on the interrelated problems of lubricating oil quality and consistency, mechanical systems performance, durability and wear, energy

conservation, and protection of the environment.

In my remarks at the 1976 Recycled Oil Conference, I quoted a statement by Mr. Ted

Gordon, President of the Futures Group. Mr. Gordon said: "The use of recycling materials as a strategy to respond to increasing materials costs and uncertain availability is, of course, not new. What

has changed are the equations by which the economics of such activities

are evaluated.

"

In light of the petroleum situation of the last few months, these words are even more appropriate and important today. And the equations governing the economics of recycling and durability are still changing rapidly, almost always providing even stronger pressure in support of recycling. The pollution aspects of oil recovery and recycling are also gaining

momentum, and the EPA hazardous waste regulations due in a few months will no doubt substan- tially affect these economic equations also. The Energy Policy and Conservation Act of 1975 gave NBS some formidable technical challenges with respect to developing test procedures for the "substantial equivalency" of recy- cled oil to virgin oil. The Recycled Oil Program has completed its work on Phase I, Test Procedures for Recycled Oil Used as a Burner Fuel, and has transmitted these test procedures

to the Federal Trade Commission. We are now addressing Phase II, the most difficult challenge, as well as perhaps the most important, namely test procedures for recycled oil used as motor oils. In this phase we will need the input and guidance represented by this audience.

In closing, let me once again provide some historical data. At the first Recycled Oil Conference, in 1976, there were 69 registrants. At the second Conference, 1977, there were

171 registrants. Today, at the start of this Conference, we already have over 170 registrants. It is very encouraging that all of you have taken the time from your busy schedules

to be here with us. Certainly, we at NBS feel that providing for the exchange of information

is a vitally important aspect of our work, and we are most pleased to co-sponsor this meeting. Thanks again for coming, and we look forward to the contributions you will make. Ernest Ambler

Director

National Bureau of Standards

3

JOINT CONFERENCE ON MEASUREMENTS AND STANDARDS FOR RECYCLED OIL/SYSTEMS PERFORMANCE AND DURABILITY

P. Strigner

National Research Council of Canada Division of Mechanical Engineering

Ottawa, Canada K1A 0R6 Introductory Remarks

As a joint sponsor of this conference dealing with test methods and standards for recycled oil used as automobile crankcase oil with NBS Recycled Oil Program and MFPG, it is appropriate for me also on behalf of the officers and members of ASTM D-2, Technical Division

P and its sections to extend to you a warm welcome. May your presence here not only allow you

to justify your journey to your employer, but also to enhance the proceedings. Judging by the program contents and the previous NBS recycled oil sessions organized by the Recycled Oil Program Manager, Don Becker, in all probability your stay here this week will meet this desirable dual objective. Unquestionably, the blend of new oil analyses and used oil mon- itoring for oil condition and engine or machine health is warranted.

To be fair the bulk of the credit for organizing and all of the credit for initiating

this outstanding program must go to NBS and its outstanding personnel, five of whom I have had

the pleasure of working with: Dr. J. J. Comeford, Dr. E. Passaglia, Dr. S. Hsu, Dr. H. Yakowitz and of course, Mr. Becker. Touching on Technical Division P activities the following points are worth mentioning:

1) Technical Division P formed in December 1977 now has over 100 members. It meets twice a year at regular ASTM D-2 meetings.

2) NBS, which had a strong hand in the organization of Technical Division P, is a major

contributor to its activities. Much needed basic laboratory work undertaken by the Recycled

Oil Program can very well lead to appropriate ASTM volunatry standards.

3) Contributions by the oil industry especially, but also by some additive and equipment

manufacturers and users and Federal Government agencies, are super.

4) Contributions by the Association of Petroleum Re-refiners and by the re-refiners

themselves need to be enlarged. Only Bob Pedal 1 of Morco and George Booth III of Booth Oil have contributed in a large measure. One factor that could strengthen APR's contributions is an improvement in the members' own laboratory facilities, more regard for evaluation of product properties, and more verbal input and presence at Tech P meetings^ along with active participation in projected laboratory programs.

5) Tech P acts as a strong forum bringing together producer, user, and general interest

participation.

6) Regrettably, Tech P is slow in the development of voluntary standard methods and specifications relating to recycled petroleum products and lubricants and/or rubber stamping

existing ones relating to virgin products. Every effort will be made to speed up. One obstacle is the general absence of many ASTM standard specifications for lubricants. To meet

pressures from ISO TC-28, such standards are now slowly being generated in ASTM D-2 in cooperation with other organizations.

7) To date, Tech P has aided the U.S. Army in updating MIL-L-46152 to accommodate

re-refined engine oils; has set up a task group in cooperation with NBS to study base stock consistency; is proposing some changes to ASTM D396 and VV-F-815d fuel specifications; is collecting virgin and recycled hydraulic fluid and industrial oil specifications; is preparing

5
definitions for a number of recycled oil terms, and has asked some D-2 Research & Development Divisions to develop a number of standard methods, e.g., for PCBs in oil and for metals in used oils and base stocks by rapid instrumental techniques. Of course, first hand infor- mation and minutes are readily available from Tech P officers.
BRIEF OVERVIEW OF THE NBS OFFICE OF RECYCLED MATERIALS (ORM) Harvey Yakowitz

Chief, Office of Recycled Materials

National Bureau of Standards Washington, DC 20234

The Office of Recycled Materials was created in the National Bureau of Standards re- organization of April 9, 1978. At present, this office consists of two programs, the Resource Conservation and Recovery Program and the Recycled Oil Program. These two efforts have existed at NBS since 1976. Both efforts were created in response to Congressional directives

naming NBS to carry out specific tasks. Since you will be hearing more about the NBS Recycled

Oil Program in a few minutes, let me say a few words about the NBS Resource Recovery Program. The Resource Conservation and Recovery Act of 1976 (PL 94-580) enacted October 21, 1976, directs the Secretary of Commerce, acting through NBS, to hold public hearings and publish

guidelines (by October 21, 1978) for the development of specifications. These specifications

are needed for the classification of materials which can be recovered from waste now destined

for disposal. NBS is authorized to undertake work of this nature by 15, USC 272 which

describes functions of the Secretary of Commerce to include "the determination of physical constants and properties of materials when such data are of great importance to scientific or manufacturing interests and are not to be obtained of sufficient accuracy elsewhere."

The nation generates about 145 million tons of municipal solid waste. Currently, over

93 percent of this waste is disposed by open dumping, "sanitary" landfilling, incineration or ocean dumping, all environmentally unsound methods. Alternatives to land disposal methods must

be found since many cities in the U.S. will run out of suitable solid waste disposal sites by

1982. A method to do this is to separate metals, glass, and the organic fraction of this refuse from one another thus providing a potentially marketable set of commodities.

Large quantities of potential resources are being discarded in the waste. According to figures compiled by EPA, we annually discard about 20 percent of the nation's tin and aluminum

requirements-, 10 percent of its ferrous metal requirements; enough glass to replace a year's

needs for glass containers-, and enough organic material, which if converted to energy could provide up to 2 percent of current energy needs.

In enacting PL 94-580, the Congress stated that:

1. Millions of tons of recoverable material which could be used are needlessly

buried each year.

2. Methods are available to separate usable materials from solid waste.

3. The recovery and conservation of such materials can reduce the dependence of the United States on foreign resources and reduce the deficit in its balance of payments.

In order to carry out the program, NBS is conducting several projects to characterize

recovered materials and establish the guidelines mandated in PL 94-580 and to evaluate

existing, proposed and/or required specifications for these materials against the guidelines.

The materials in question include ferrous metals, nonferrous metals (primarily aluminum),

glass, paper, plastics, rubber, certain construction wastes, and refuse derived fuels. This provides a very short overview of the NBS Resource Recovery Program and our responsibilities

there.

7

CONFERENCE OBJECTIVES

D. A. Becker Recycled Oil Program

National Bureau of Standards Washington, DC 20234

This conference is co-sponsored by ASTM Technical Division P, the Mechanical Failures Prevention Group, and the National Bureau of Standards (NBS) Recycled Oil Program. Paul Strigner has given you some insight on the workings of the ASTM Tech. P, and in a few minutes

Bill Ruff of NBS will provide his comments on behalf of the Mechanical Failures Prevention

Group. At this time, I will take several minutes to describe what the NBS Recycled Oil Program would like to see occur during this conference.

First, there are three general objectives which I discussed at our previous conferences,

and which I hope will also be present at this Conference. They are as follows:

1) To obtain information and input to the NBS Recycled Oil Program from all re- levant sources;

2) To report to you on the directions and progress we are making on our legisla- tive mandates; and

3) To bring together in one place all of the different people who are involved with the various aspects of lubricating oils--the producers, the testers, the

users, the recyclers, and the regulators—to discuss new developments and re- cent changes in oil recycling, and the needs for measurement methods and stan- dards for recycled oil. During the Conference, we have tried to provide many opportunities for you, the participants, to meet and talk with the other parti cipants--at coffee breaks, receptions, even on bus rides.

In addition to the above objectives, there is an additional objective oriented more

towards the primary topic of this conference, engine oils. This objective is to provide a forum where the concerns and questions about possible widespread increased use of re-refined constituents in engine oils can be openly and objectively discussed. This conference, along with the many other NBS activities, will be important to establishing our Program as a strong, objective and technically oriented effort to establish the scientific and technical require- ments for the effective reuse of re-refined oils.

In conclusion, when this Conference is concluded, I trust that we will be able to say that it has helped to provide a focal point on the subject of recycled oil--a forum in which

hard technical questions can be asked, discussed, and answered, either now or after additional studies. I feel that this focus on the technical questions, rather than on political questions or emotional questions, can thus provide a strong foundation on which effective oil recycling can increase, and will provide for the optimum utilization of our limited resources

of petroleum lubricating oil.

9

CONFERENCE OBJECTIVES

A. W. Ruff

Mechanical Failure

National Bureau Washington,

Prevention Group

of Standards

DC 20234

Joint sponsorship of this Conference by the Mechanical Failures Prevention Group re- flects the focus of MFPG technical activities on failure prevention and reliability in me- chanical systems. This group, which is sponsored by NBS, ONR, NADC, DOE, and NASA, has the express purpose of stimulating voluntary cooperation among all segments of the national sci- entific and engineering communities to reduce the incidence of mechanical failure. The MFPG interest in oil analysis and monitoring of systems performance provides a strong common

interest with the NBS Recycled Oil Program. The MFPG operates through four technical com- mittees as listed in the Conference Program. One of these, the Materials Durability Eval- uation Committee, is responsible for the MFPG role in this Conference, particularly in or- ganizing Sessions 4 and 7. The central theme of these invited papers is on system condition

monitoring in lubricated systems, and on the related aspects of performance and durability. These are regarded as critical issues in the overall program for effective use of re-refined

lubricants.

Session 1 RECENT DEVELOPMENTS IN RECYCLED OIL

13

National Bureau of Standards Special Publication 584. Proceedings of Joint Conference

on Measurements and Standards for Recycled Oil/Systems Performance and Durability held at

NBS, Gaithersburg, MD, October 23-26, 1979. (Issued Nov. 1980)

ACTIVITIES OF THE NATIONAL ASSOCIATION OF OIL RECOVERY COORDINATORS

Don Eastep

National Association of Oil Recovery Coordinators

Illinois Institute of Natural Resources

Springfield, IL 62708

As your first speaker of this morning, let me open by saying how happy I am that we can finally meet face-to-face. I have spoken to many of you by phone over the past year and a half, and I hope to be available tonight to go into detail with anyone on program specifics.

Last April the second, in Salt Lake City, representatives from 12 states met to discuss

oil recovery. As a result of that meeting, the National Association of Oil Recovery

Coordinators was formed. Membership in the Association was easy—be a member of Government

and interested in the development of an oil recovery program in your state. One of our goals

was to standardize our printed materials, such as posters, pamphlets, radio and TV PSA's, and

news releases. This was tested during the charter meeting by making comments on the API Language that would go on the oil cans sold in New York. It was recommended that the API member present, Harold Tiffany, suggest that all motor oil sold in the U.S. be so labeled.

This language was accepted by New York State and our other recommendation is being considered. Another one of our objectives was to create an organization which would give us a voice

within the industries we work with. As the association has grown to 35 states, so also has our voice become more effective. When the Association first began, a number of the interest groups said they wanted to

help, and for the most part, they just talked. They talked about incentives, promotional

material, and technical assistance. It was not until we began to grow that these offers

became real. In Illinois, one company donated 10 000 bumper stickers. Another company

offered us space in their national advertising as well as having their ad agency work with us. Public service radio spots were developed by one station which are being used now by several

states. Professionally made video tape messages were prepared by the State of Oregon and have

been re-edited for use by several states. Through the technical assistance program of the USEPA (Peer Match), it is possible for members to travel to other states. (This was how the Salt Lake City Meeting was funded.) The re-refining industry has been most cooperative. Companies from all around call and ask for the name of their state coordinator. I have received reports from coordinators telling of their success in getting programs started. They

all say the same thing, without the cooperation of the interest groups, they would still be in

a development stage instead of implementation.

Recently, I met with an inventor who had a plug for an oil pan. This would allow the do-it-yourselfer to change oil quickly and cleanly. The reason I mention this is to show that

others are interested in the business of oil recovery. I can see in the next few years a new

look to the re-refining industry. This will happen when the people who change oil are made

aware of the value of recovery and the industry gets more aggressively involved in that

recovery. We in the National Association of Oil Recovery Coordinators are dedicated to that

end. To work closely with the re-refiners, the major oil companies, the retailers of oil to the do-it-yourselfer, service stations and recycling centers, where used oil is brought in, and the scores of civic groups needed to coordinate these programs on the local level. Let me talk a bit about the problem. How big is it and what can we do to help alleviate

it. According to recent estimates 1

, in 1978 the total lubricant sales in the U.S. were

259 100 000 gallons. Of this, 1 233 000 000 gallons went to the automotive market as crankcase oil and about 35 percent of this volume was consumed by the engine or lost through

15
leakage. That gives us over 801 450 000 gallons of used crankcase oil. If 60 percent of the motor oil sold is through other than service stations, we have a do-it-yourself market that is responsible for 480 870 000 gallons of recoverable oil a year. If we add to that 50 percent

of the non-SAE engine oils, such as railroad diesel, marine, and aircraft--the total is 462 536 000 gallons. The general industrial lubricants sold in 1978 were 1 016 000 000 gallons. Figuring

about 60 percent recovery rate, we have another 610 000 000 gallons. The overall total of recoverable oil then would be more than one billion gallons.

The re-refining industry currently handles about 150 000 000 gallons a year (35 000 000 gallons automotive, 115 000 000 gallons industrial). This means that there is more than 850 000 000 gallons per year not accounted for! Where is it all going? An unknown amount of industrial oil is being recycled in-house.

A great deal of automobile oil is being dumped into sewers or just on the ground. Some

of it is being burned, causing a serious environmental hazard; much of it goes to landfills. The only thing these methods have in common is that the oil is being disposed of--not

recovered.

The economics of recovering this much oil is staggering. If we could recover 200 million

gallons and re- refine it, we could have 150 million gallons of lube stock to place back on the

market. On the other hand, based on API estimates of 1.5 percent lube stock per 42 gallons of crude, we would have to refine 238 000 000 barrels of crude to have the same amount (238 x 42

x 1.5% - 150 million gallons). To satisfy this segment of the market, it would cost us, in 1979 dollars, at $23.50 a barrel, $5 593 000 000. When the price goes to $40.00 a barrel, it will be $9 520 000 000. I realize that the rest of the barrel is also necessary. I also realize that others are working in areas dealing with the "rest of the barrel". The President has said we will cut down on the import of crude. He has also given

several guidelines as to how we can take up the slack. At this time, very little has come

from Washington regarding used oil recovery as a viable alternative. Tomorrow morning I will

be meeting with members of the White House Staff to discuss the possibility of a National Oil Recovery Program. It would be premature to have any discussion of this at this time. However, I will advise the members of the Interagency Committee on Resource Recovery (IC0RR)

of the results.

To conclude, what can we do to help? I think the most important one thing is to educate

the public; to inform them of the problem; to show them that used oil, even in quantities of one gallon, is worth something. It does not have to be dumped on roads for dust control. The farmers (one of the largest individual do-it-yourselfers) do not have to use it to kill weeds

or pour it into a pit for their pigs to soak in.

I read somewhere once that it is better to have tried to do something and failed than to try nothing, and succeed. For years nothing has been done quite successfully. It is time now

to try, not with the cloud of failure hanging over us, but with the idea in mind of how

successful we will be. How much can we help with our energy problems--how much cleaner can we make our environment— how much money can we save? The answer is not just around the corner

but it is closer now than ever before.

^im Helms, Sun Oil Co., The Changing Lube Market, Annual ASLE Meeting, May 1979.
National Bureau of Standards Special Publication 584. Proceedings of Joint Conference

on Measurements and Standards for Recycled Oil /Systems Performance and Durability held at

NBS, Gaithersburg, MD, October 23-26, 1979. (Issued Nov. 1980)

THE MARYLAND OIL RECYCLING LEGISLATION

C. R. Willey and D. G. Phillips Maryland Environmental Service Maryland Department of Natural Resources

60 West Street

Annapolis, MD 21401

1. Introduction

Maryland's 1978 Used Oil Recyling Act is the latest of a series of steps taken by the State to control oil and oily waste discharges into the environment. Before discussing

details of this new law, and the program that evolved from it, it seems appropriate to review

some of the actions that preceded its passage by the Maryland Legislature.

In the early 1970' s Maryland began to recognize the magnitude of its waste oil problem

[l] 1. It was estimated that some 18.5 million gallons of waste oil was generated yearly in the state, with about 7 million gallons estimated to be crankcase type oils [2], and, as a result of a decline in the oil recycling industry in the 1960's, many generators of waste oil were without means of disposal other than into the environment in one way or another. In addition, it was felt that the State needed to do more to prevent oil spills and respond to needs for oil spill cleanup.

As a result, legislation was passed granting the Department of Natural Resources broad authority to license the handling and storage of oil, to create the "Maryland Oil Disaster

Containment, Clean-up, and Contingency Fund", to promulgate regulations, develop an enforce- ment program to control discharges of oily wastes, and to carry out other functions necessary

to prevent or control oil and oily waste contamination of both the land and waters of the State [3]. At the same time, the Maryland Environmental Service, which was then a newly formed

State "waste management" agency [4], began to examine ways to improve the collection and

reuse of waste oils [2,5,6]. The 1974 oil embargo, however, revived the oil recycling in- dustry such that adequate collections were resumed, and plans for a State supported collection and recycling program were abandoned.

In 1975, then, with the State's regulatory and oil control program underway, waste oil collection by the recycling industry improved, and major sources of oil contamination under

control, attention began to focus on "do-it-yourself" automotive crankcase waste oil, which

still had no place to go but on the land, in the garbage, storm drains, and the like. Re- ports indicated that the numbers of people involved in this practice was increasing rapidly

and that as a result several million gallons of used oil was entering the environment in Maryland each year. The need to collect and reuse this oil thus came to the attention of the State Legislature.

In 1976, after several meetings of an ad hoc task force to review proposed legislation,

an oil recycling act patterned after part of the Federal Energy Administration (FEA) "Model Used Oil Act" [7] was prepared and introduced in the 1977 Maryland Legislature. Although the

act was passed, it contained one requirement objectionable to the oil industry-- that oil be sold in a "resealable" container. Subsequently, after a hearing, it was vetoed by the Governo

of Maryland. When reintroduced in the 1978 session without this requirement, with the support

of environmentalists and industry alike, the act was passed and became law in May of 1978. The primary intent of the law was environmental protection and, therefore, was made the respon

sibil ity of the Maryland Department of Natural Resources [8]. Figures in brackets indicate the literature references at the end of this paper.

17
2. The Maryland Used Oil Recycling Law Highlights of the new law are that it: 1) Requires an education program to inform the public of the needs for and the benefits of collecting and recycling used oil in order to conserve resources

and preserve the environment.

2) Requires persons regularly engaged in the business of selling lubricating oil for use off the premises to post and maintain, at or near the point of display

or sale, legible signs informing the public of the importance of proper col- lection and disposal of used oil, and how and where used oil may be disposed

of.

3) Establishes a used oil information center to explain local, state, and federal

laws and regulations governing used oil and to inform holders of quantities of used oil on how, where, and in what manner used oil may be properly disposed

of. 4) Encourages the establishment of used oil collection and recycling programs and provides technical assistance to persons organizing these programs.

5) Encourages the use of labeling for oil containers to inform the user of the importance of proper collection and disposal of used oil.

6) Encourges State Inspection Stations, service stations, and other establishments with suitable facilities to serve as collection facilities for the deposit of used oil, with no cost to a person making the deposit. Each desig- nated facility shall post and maintain a sign which indicates the facility is designated as a used oil disposal location. Each designated facility regularly shall remove and dispose, or have removed and disposed by used oil col- lectors, the accumulated oil in a manner as required by law. 7) Makes it illegal for a person to dispose or cause to be disposed any used oil by discharge, dump, or deposit into sewers, drainage systems, surfaces or ground waters, any waters in this State, or by incineration or as refuse, or onto any public or private land unless such land is designated by the State or by any of its agencies or political subdivisions as a collection facility and

the used oil is placed in a receptacle or container installed or located on the property.

8) Establishes Penalties - a) Any person who violates any provision of this section of the law or any rule or regulation issued under the Act, in addition

to any other penalties specifically provided by law, is subject to a civil penalty not exceeding $250 for each violation, b) Any person who commits a second or subsequent violation, of any provision of this section or any rule

or regulation issued pursuant thereto, in addition to any other penalties specifically provided by law, is guilty of a misdemeanor and, upon conviction,

in a court of competent jurisdiction, is subject to a fine not exceeding

$1000 or imprisonment not exceeding two months, or both, with costs imposed

at the discretion of the court.

3. Responsibilities

To implement the new law responsibilities were split between two agencies of the Depart- ment of Natural Resources. Enforcement became the jurisdiction of the Water Resources Admini- stration Enforcement Program previously established to handle pollution violation. The educational program, designation of oil collection stations, and other aspects of the law were assigned to the Maryland Environmental Service to be carried out in conjunction with other waste recycling programs.

18
4. The Maryland Environmental Service Program

The first step taken by the Maryland Environmental Service upon passage of the law was

to provide the required "collection facilities" where used crankcase oil could be deposited. Most licensed Automobile Inspection Stations (about 1/3 of the stations, garages, and car dealerships in the State) were contacted through the Automotive Safety Enforcement Division

of the Maryland State Police over a two month period. Of those contacted, 410 agreed to serve as a collection facility; 493 refused. Additional survey programs were carried out by several volunteer organizations to bring the list of collection facilities up to just over

500 stations by midsummer of 1978. (Since then, the number approaches 700.)

Step two was a letter to all 23 counties and Baltimore City to inform them of the law and request that each of them designate a person to assist with implementing the used oil recovery program. Step three was to select a symbol that could be associated with the oil recycling program. Formation of a task force to do this was considered, as well as a contest; both were

rejected because of the time involved. Instead what appeared to be an appropriate symbol was simply created. It was shown to oil industry representatives and others who had sup- ported the legislation to determine if the symbol was acceptable, and it received their

approval. The symbol and a sign created to identify used oil "collection facilities" is illustrated in figure 1. Step four was the preparation of a sign for display (under the law) by persons engaged

in the business of selling oil for off-premise use. Various trade associations were con- tacted regarding the sign and it was agreed to keep the sign small. A 28 x 34 mm sign, figure 2, was printed on heavy paper for distribution to major trade associations and di- rectly to the main offices of major stores selling oil. With the completion of these steps, a dedication ceremony was held August, 1978, as the first move bringing the program to the attention of the public. The attendance of several

key elected officials helped to assure TV coverage, and press releases were sent to radio stations and newspapers throughout the State. At the same time, an "information office" was established at the Maryland Environmental Service office to supply locations of used oil collection facilities, names of licensed oil handlers to stations needing oil pick-up service, and other information on proper disposal of

oil. Other steps taken have been: 1) the distribution of signs to collectors and oil re- tailers through county coordinators; 2) periodic meetings with county coordinators to en- courage the use of the news media to publicize the Program; 3) distribution of brochures;

4) inclusion of introduction on proper disposal of oil and oil recycling in the Maryland

Driver's Education Program; 5) inclusion of a section on oil recycling in the Maryland

Driver's Handbook; and 6) the recent preparation of brochures to be distributed by the Maryland Motor Vehicle Administration to all persons renewing automobile tags at their

offices. Maryland also has joined with other States in encouraging oil companies, through the Maryland Petroleum Association-State Division of the American Petroleum Institute, to adopt

the following labeling of oil: "Don't Pollute - Conserve Resources - Return Used Oil to Collection Center"

5. Evaluation of the Program

Does the program work? Second question: how do we know?

Oil handlers operating in Maryland are required by law to report quantities of crankcase

and noncrankcase oil collected. The following amounts for crankcase oil have been reported:

19
MARYLAND USED

OIL COLLECTION

FACILITY

SAVE ENERGY

AND PROTECT YOUR

ENVIRONMENT

DEPT. OF NATURAL RESOURCES — MARYLAND ENVIRONMENTAL SERVICE

Figure 1. Reproduction of 40.6 cm (16 in) by 60.9 (24 in) metal sign used by the State of Maryland to identify used oil collection facilities.

20
NOTICE TO MOTOR OIL BUYERS DO YOU KNOW? — THE STATE OF MARYLAND NOW HAS A LAW WHICH FORBIDS YOU TO DUMP USED OIL IN SEWERS, ON LAND, IN REFUSE OR IN THE WATER. FIRST TIME VIOLATORS ARE SUBJECT TO A MINIMUM

OF A CIVIL PENALTY UP TO $250.00.* — YOUR USED OIL CAN BE RECYCLED TO CONSERVE ENERGY AND PROTECT THE ENVIRONMENT FROM POLLUTION. — YOU CAN TAKE YOUR USED OIL TO THE SERVICE STATIONS AND RECYCLING CENTERS LISTED BELOW

OR TO ANY FACILITY DISPLAYING THE "RECYCLE-OIL-HERE" SYMBOL SHOWN ABOVE.

FACILITIES IN THIS AREA THAT ACCEPT USED OIL FOR RECYCLING INCLUDE:

'EFFECTIVE JANUARY 1, 1979 ENFORCEMENT PROGRAM, WATER RESOURCES ADMINISTRATION, MARYLAND DEPARTMENT OF NATURAL RESOURCES. FOR INFORMATION ON RECYCLING AND COLLECTION FACILITIES CONTACT THE MARYLAND

ENVIRONMENTAL SERVICE, PHONE 301-269-3355.

Figure 2. Retyping of sign required by the State of Maryland to be posted by sellers

of oil for off-premise use. (Original of sign could not be reproduced for

publ i cation.

)

21
January through June 1978 - 2.74 million gallons July through December 1978 - 3.69 million gallons January through June 1979 - 4.52 million gallons

Substantial increases in the quantity reported collected have occurred during the brief period of reporting; however, it is impossible to determine what portion of the increase was

the result of the recycling program, increased collection activity, or just better reporting.

In July of 1979, a survey was made of 24 collection facilities in the Annapolis - Baltimore areas of the State. Operators were asked about the numbers of people returning oil and the location of the "Recycle Oil Here" sign (fig. 1) was checked. Answers ranged from

none to 40 gallons per week with the average answer being a few gallons per week. Signs were displayed in windows or outside at 2/3 of the stations contacted. A problem noted was that

no one person could be counted on to know how much oil had been returned for recycling. Stores retailing oil for off-premise use also were checked for presence of their re- quired sign and the compliance was found to be rather poor. The problem seems to be one of educating individual store managers; although store headquarters personnel have been cooperative in the distribution of signs, it appears that not enough has been done to cause the individual stores to display the signs. Judging from numbers of calls inquiring about oil collection facilities, people are learning about the law and the program. Progress in this respect though, has been hindered

by a lack of funds. The law, unfortunately, was passed without supporting funds so that it has been necessary to manage the program with existing staff and modest support ($10 000) from Maryland's Energy Administration and assistance from the State's Motor Vehicle Administration.

We believe we have done well with the resources available to us, but would suggest for other

States of a similar size (4 million population) that to start such a program (exclusive of enforcement) that the program be provided with at least a staff of two, initially, and a budget of at least $75 000, exclusive of salaries. This amount would support the purchase of signs to identify oil recycling centers, a film for use in driver education training, production of TV and radio spots, advertising and other material for public education parts of the program.

6. Future Plans

The program is now seeking funds for more intensive efforts to inform the public of

the law, the availability and locations of collection facilities, and the need for recycling

oil. Emphasis will be placed on the energy savings aspects of recycling as well as the environmental

.

There also appears to be a need for more public collection facilities. People using gas and go locations, which lack oil storage tanks for recycling, may be reluctant to drop oil at service stations they do not patronize. Collection at places such as fire departments may encourage greater participation.

A third area is communication with stations and car dealerships serving as collection

facilities. Information must be made available to them to keep up their interest in the program and to continue educating new workers about the program.

7. Conclusion

In 1971 it was estimated that 28 percent of automotive oil was changed by the "do-it- yourself" person. The estimate is now 50 percent. Based on automobile registrations and three gallons per car per year, an estimated 3.3 million gallons of waste oil, therefore,

is now drained from automobiles each year. It is indeed important that we provide for the collection and reuse of this oil.

22
References

[1] Shields, W. H. and Miles, W. A., Used Oils: A Waste? Or a Resource?, Maryland Environmental Service and Maryland Department of Health and Mental Hygiene, p. 32 (1971).

[2] Waste Oil Recovery Practices: State of the Art, Report for Maryland Environmental Service and the U.S. Environmental Protection Agency by Environmental Quality Systems,

Inc., Washington, DC, p. 250 (1972).

[3] Oil Discharge Containment, Control, and Clean-up, Natural Resources Article, Annotated

Code of Maryland, Title 8, Subtitle 14, Article 8-1411 (1974).

[4] Maryland Environmental Service Law, Natural Resources Article of the Annotated Code of Maryland (Sections 3-101 to 3-131, 1979 Supplement) (1970).

[5] State of Maryland Waste Oil Recovery and Reuse Program, EPA Technical Report, 670-12-

74-013, p. 248 (NTIS No. PB-234 446/3BE) (January, 1974).

[6] Waste Oil Recovery and Reuse Program - Residue Management, Report to the Maryland Environ- mental Service and the U.S. Environmental Protection Agency by GCA Corporation, Bedford,

MA, p. 131 (April, 1975).

[7] A Model Used Oil Recycling Act, Prepared by W. A. Irwin, Environmental Law Institute, Washington, DC for the Federal Energy Administration (1976).

[8] Maryland Used Oil Recycling Act, Natural Resources Article of the Annotated Code of Maryland (Section 8-1411.1, 1979 Supplement) (1978).

23

National Bureau of Standards Special Publication 584. Proceedings of Joint Conference

on Measurements and Standards for Recycled Oil /Systems Performance and Durability held at NBS, Gaithersburg, MD, October 23-26, 1979. (Issued Nov. 1980)

RE-REFINING IN INDIA

M. K. Bhargava

Chemoleums Private Limited Thiruneermalai Road Chromepet Madras 44 Madras, India The Indian Institute of Petroleum, Dehra Dun made available its know-how for re-refining

used engine oil to about 30 entrepreneurs. Out of these only a handful are utilizing their

process. However, there are about 30 members in Petroleum Re-Refiners Association of India. After the certification scheme, as announced by the Ministry of Petroleum is complete, a true picture would emerge as to the actual number of re-refiners engaged in the proper re-refining

of used engine oil. There do exist a large number of backyard reclaimers whose existence be- comes possible due to high price of the virgin engine oil. The cost of the virgin oils are: Technically Equivalent MIL-L-2104A/ DEF Series DEF2101C 2101D MIL-L-2104B 3 oil (Rates are packed in 205 liter drum or * 54 U.S. gals.

)

1. Price per liter Rs. 6.81 Rs. 6.98 Rs. 7 23 Rs. 7 73

2. Price per U.S. gal

.

Rs. 25.78 26.42 27 37 29 26

3. Price per U.S. gal

.

$ 3.22 $ 3.30 3 42 3 66

The backyard reclaimer found a ready market for his finished product by mixing improperly re- claimed oil with virgin oil or selling it as such in bulk or packed in smaller containers of the well-known brands. Used Oil The used oils are sold by large fleet owners/government state transport undertakings in open auction and by the private fleet owners and other generators of used oil negotiation.

The price of used engine oil in bulk ranges from Rs. 2/-per liter to Rs. 3/-per liter

($1 per U.S. gal. to $1.40 per U.S. gal.). This high price requires a larger working capital

for the recognized re-refiner. Fortunately, the used engine oil in our country has a lower additive content, is void of lead and is generally monogrades, thus making the re-refining comparatively easier than the European and American used engine oils which have a higher

additive content, possibly contain lead, and are generally multigrade. The draining in our country is mainly from diesel engines. The total consumption of lubricants in India is 500 000 tons of which about 5 percent

maximum comes to the recognized re-refining industry and the balance is either burnt or discarded. The Government of India has been encouraging in particular the Government

undertakings to set up their own captive units for re-refining but these have not been so successful and the output of captive units is used for topping up purpose.

I would conclude by saying that "Oil is Politics" and with the establishment of a re-refined engine oil specification and registration of the re-refiners in our country,

it is hoped that the Government will take a more positive step in encouraging the re- refining industry in our country (see attachments 1 and 2). 25
ATTACHMENT 1 Indian Specification for Re-Refined Automotive Internal Combustion

Engine Lubricating Oil

1. Introduction

The Indian Standards Institution (ISI) was established in 1947. The main objective of the Indian Standards Institution could briefly be described as being the promotion of stan- dardization in the country through the preparation of specifications and the administration

of quality certification mark scheme for products that comply with these specifications and

it is governed by the Indian Standards Institution (Certification Marks Act 1952).

2. Specification

Generally, British and American standards have been adopted insofar as the petroleum

products are concerned. Toward the end of 1976, the Minister of Petroleum announced with a view to curb the sale of spurious lubricating oils that all lubricants sold in the country

must compulsorily carry ISI Mark. This announcement naturally caused anxiety in the trade, and in particular to the smaller oil companies who immediately applied for ISI Mark. Since

the current specifications did not include performance and other stringent tests it became necessary to review all the lubricating oil specifications. The Ministry of Petroleum di- rected ISI to do so and ad hoc study groups were formed. In 1977, the study group for auto- motive oils submitted its report and in respect to the re-refined oil reported that since

the feed stock was obtained from different sources it was very difficult to qualify the re-refined product without full engine testing. Thereafter, based on the representation made

by the Petroleum Re-Refiners Association of India to the Minister of Industries it was de- cided in early 1978 that ISI would give its Mark to the Re-Refined Oil and the Re-Refining

Industry would be registered with the Ministry of Petroleum, and the Ministry of Petroleum

in turn would make available the used oil to the re-refiners and such other virgin base oils

and additives they would require. Accordingly, after much discussion the draft Specification for Re-Refined Automotive

Internal Combustion Engine Lubricating Oil was finalized. In June 1979, the Ministry of Petroleum announced a scheme for registration of the re-refining units as per details

enclosed.

The specification approved for the re-refined engine oils is: 1) HD Type 1 tech- nically equivalent to DEF 2101/MIL-L-2104A; 2) HD Type 2 technically equivalent to DEF 2101D; and 3) HD Type 3 technically equivalent to obsolete MIL-L-2104B. The specification requires

that the re-refined base oil corresponds to the requirements as in table 1 which follows. The physico-chemical requirements of the re-refined engine oil is as shown in table 2 which follows. The Department of Petroleum will depute a Technical Committee consisting of six members

to determine the eligibility of the re-refining units for registration. This scheme has just been initiated and the period for registration will expire on September 26, 1979, pro- vided no further extension is granted. The implementation of the scheme can only be known after the registration is completed.

The qualification certificate would be valid for 4 years. Full specification tests, including engine tests, are required to be carried out on one batch initially. Thereafter,

the following are the requirements:

1) The physico-chemical requirements on both base stock and finished oil shall be met on each batch.

2) The same additive package and dosage to meet the required performance

level shall be used for all subsequent batches.

26
3) One screening test for oxidation stability and bearing corrosion characteristics

on Petter Wl/CLR L-38 shall be conducted once in each year to the satisfaction of the qualifying authority according to the procedure laid down by it with regard to sample collection and evaluation.

The specification suffers from the following:

1) The virgin base stock should be allowed to meet the viscosity requirements

for some of the grades, particularly SAE 50. 2) The finished oil is required to be labeled as "Re-Refined Engine Oil".

3. Marking Fee

ISI has announced the marking fee for re-refined engine oil as:

Rs. 10.00 per unit (1 kilo liter) for 1500 units

Rs. 8.00 per unit for the next 1500 units

Rs. 5.00 per unit for the remaining units with a minimum of Rs. 15 000/- for an operative period of one year. In addition, the ex- penses for panel members for qualification approval and other tests such as qualification of engine test, approval of blending facilities and scrutiny of engine test data, will be borne

by the manufacturer.

4. Levels of Control

ISI has announced the following quality controls:

1) All the physico-chemical tests as contained in the enclosed tables 1 and 2 for re-refined base oil and re-refined automotive combustion engine lubricating oil are to be carried out for each batch.

2) For every fifth batch, phosphorus, chlorine, sulphur, barium, calcium, zinc, and sulphated ash test is to be carried out.

3) Once a year Petter Wl/CLR L-38 test for oxidation stability and bearing corrosion characteristics is to be carried out.

4) Once in four years, engine performance tests.

5. Reaction of Engine Builders to the Re-refined

Engine Oil Specification

The initial response from the two major engine builders, Messrs. Ashok Leyland, Ltd., and Tata Engineering Locomotive Company Ltd. (TELC0), in our country has been positive. They have called for samples of re-refined engine oils for evaluation in their laboratories

and field tests. It is hoped, within a short time, all the engine builders will, in principle, accept the re- refined engine oils.

27
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29
ATTACHMENT 2 Government of India Ministry of Petroleum and Chemicals

and Fertilizers

(Department of Petroleum)

Shastri Bhavan

New Delhi The Director of Industries 26th June 1979

Subject: Introduction of a scheme for registration of units engaged in the re-refining

of used automotive lubricating oils. Sir,

I am directed to state that Government have decided to introduce a scheme of voluntary registration of Units engaged in Re-refining of Used Automotive Internal Combustion Engine Lubricants with the objective of ensuring that the end products conform to the desired quality standards while simultaneously guarding against the possibility of circulation of off specification and poorly reclaimed lubricants which not only cause serious damage to industrial equipment and machinery but can also be potential health hazard to the per- sons who handle them. The scheme provides for preliminary screening of the applications

received from the units intending to get registered with the Department of Petroleum, followed by physical inspection of the facilities and know-how available with them for quality re-refining of used automotive lubricating oils. Simultaneously, the units are also required to obtain ISI Certification Mark which would be a pre-condition for their registration with the Department of Petroleum. After the task of registration of re- refining units has been completed it is proposed to take measures with a view to en- sure that the bulk of the available Used Automotive Lubricant is supplied only to the re-refining units registered with Department of Petroleum.

A copy of the Press Note issued in the regard together with a set of detailed guidelines which are required to be observed by the Re- refining Units seeking registration is enclosed. It is requested that this scheme may be brought to the notice of all Re-refining

Units functioning under your jurisdiction.

It is further requested that immediate action may kindly be initiated to facilitate early implementation of this scheme.

V. K. Misra

Deputy Secretary to the Government of India. Press Note Government has been greatly concerned over the circulation of spurious/substandard

lubricants in the market which cannot only cause serious damage to industrial equipment and machinery but can also be a potential health hazard to the persons who handle them. The mushroom growth of backyard re-refiners and other unauthorized units, which are neither licensed nor registered and pass off their substandard products as the genuine stuff, very often in counterfeit tins and containers of the type in which well known brands of lubri- cating oils are marketed, has accordingly been a source of serious anxiety to the Government.

Such parties reportedly market their goods unscrupulously through bazaar traders, garage

owners, repair shops and bus and truck fleet operators, etc. The Central Government has already requested all the State Government/Union Territories to arrange for surprise checks both in respect to the clandestine operators as well as any of the retail outlets of the different oil companies which are suspected to be indulging in the malpractices. It has been emphasized that firm administrative action on their part would go a long way in con- taining this rapidly growing menace. Simultaneously, the oil companies have been asked

to intensify their supervision and control over the movement and delivery of petroleum

products from the lube blending plants to the recognized outlets for lube distribution

and deal severely with defaulters. The have also been advised to launch a major publicity

drive in order to bring about greater consumer awareness of the pitfalls of using sub- standard lubricants.

30
In this background, Government has considered it necessary to pay special attention to the regulation of the lube oil re-refining industry. It is not generally known that if used lubricating oil is re-refined and fortified with the appropriate additives in a scientific

manner, the resulting product is comparable in every way with virgin oil and yet has a sig- nificant price advantage over it. It is obviously desirable to encourage the production of scientifically re-refined lubricating oils in the interests of conservation of scarce petroleum products as well as economy to the consumers. The Government of India has accordingly

decided, after detailed consultation with the various interests concerned, to introduce a scheme of voluntary registration of the re-refining units so that their products may be marketed under ISI Certification. It should be mentioned in this connection that the ISI has already formulated a set of specifications covering the re-refining of automotive

internal combustion engine lubricating oils. Units which are not in a position to come

up to these ISI standards will not be permitted to be registered under this scheme.

In the first phase, the scheme will cover the re-refining of automotive internal com- bustion engine lubricating oils which account for the major proportion of the total lube

oil consumption in the country. The re-refining of used transformer hydraulic and other

industrial and secondary oils will be considered for inclusion under this scheme at a later date. It is also intended that the Re-refining Units which get registered with

the Department of Petroleum under this scheme, will be automatically entitled to the grant

of COB (Carry on Business) Licence in the event of applicability of the Industries (Develop- ment & Regulation) Act. Applications for registration are required to be made to the Department of Petroleum

through the Director of Industries of the State/Union Territories in which the Unit is

1 ocated.

All existing units engaged in the re- refining process, whether on a captive or a com- mercial basis, may submit their applications for registration on the prescribed proforma

to the Supply Division, Department of Petroleum, Shastri Bhavan, New Delhi, within a period

of 90 days from the data of announcement of this scheme. The process of registration in- cluding issuance of certificate of registration, is expected to be completed within a period

of 120 days from the date of receipt of the application in the Department of Petroleum.

New entrepreneurs wishing to enter this field may approach the Indian Institute of Petroleum, Dehradun, or the National Research & Developing Corporation, New Delhi, for acquiring the technology and know-how for the re-refining of used lubricating oils in accordance with the appropriate ISI Standards. Government hopes that this scheme will succeed in its object of making high quality

re-refined lubricating oils available to the public at reasonable prices and putting out of business the Units/Parties which are selling substandard and counterfeit oils to unsuspecting buyers. Re-Refining of Used Automotive Internal Combustion Engine Crank-Case

Lubricating Oils Guidelines for introduction of a Scheme for Registration.

1.0. Objective

1.1. In the interests of ensuring that the activity of re-refining of used lubricating oils

is undertaken on scientific lines and of ensuring desired quality standards in the final product, the Government of India has decided, after consultations with the Ministry of

Industry, DGYD, DC (SSE), Indian Standards Institutions, oil companies, Indian Institute

of Petroleum, Indian Oil Corporation (R&D Center), and the Petroleum Re-Refiners Association, that the activity of re-refining of used lubricating oils should be brought under

a scheme of registration with the Central Government. The following are the details of the scheme.

31
2.0. Eligibility for Registration

2.1. All units, whether already existing or yet to be set up, whether captive type or com- mercial type, will come under the scope of the registration, regardless of the quantum of capital investment or manpower employed.

3.0. Registering Authority

3.1. The Department of Petroleum will be the authority for registration until otherwise

notified. The re-refining units which get registered with the Department of Petroleum

under this scheme will automatically be entitled to the grant of a COB License (carrying

on business) in the event of applicability of the industries (development and regulation)

act. 4.0. Procedure of Applying for Registration

4.1. Applications for registration should be made on the prescribed proforma (Annexure I) in s'x (6) copies to the Department of Petroleum, Shastri Bhavan, New Delhi, through the Director of Industries of the State/Union Territory in which the unit is located or to be located. The application form must contain all the information specified in the proforma.

4.2. Since the scheme of registration is also linked with the ISI Certification Mark (relating to engine oil from re-refined base stock) applicants should simultaneously apply to the Indian Standards Institution, Manak Bhavan, 9 Bahadur Shah Zafar Marg, New Delhi 110 002, for obtaining the ISI Certification Mark. The application form for this purpose will be as prescribed by the ISI. 5.0. Mechanism for Registration

5.1. The Department of Petroleum will constitute a Technical Committee comprised of a rep- resentative of that Ministry, DGTD, DC (SSI), Indian Institute of Petroleum, Indian Oil Corporation (R&D Center) and Indian Standards Institution, entrusted with the responsi- bility of technical scrutiny of the application in order to determine their eligibility

for registration or otherwise. The Committee would like appropriate recommendations to the Department of Petroleum who will be responsible for a final decision. The Committee would meet as often as necessary.

6.0. Times Schedule for Application

6.1. All existing units engaged in the re-refining process whether captive or commercial

type unit may submit their application for registration on the prescribed proforma to the Department of Petroleum within a period of 90 days from the date of announcement of this

scheme.

6.2. New units may apply for registration as and when they are ready with their detailed

scheme.

7.0. Time Schedule for Registration

7.1. The process of registration including issuance of the certificate of registration will

be completed within a period of 120 days from the date of receipt of the application in the Department of Petroleum.

8.0. Time Schedule for ISI Certification Mark

8.1. Since the scheme of registration is linked to the issue of ISI Certification Mark, the

ISI formalities on this account should be completed within a period of 90 days so as to en- able the Department of Petroleum to complete the registration formalities within the stipu- lated period of 120 days.

32
9.0. Guidelines for Registration

9.1. In the case of existing re-refining units, no application for registration would

be entertained unless all the information stipulated in the proforma are furnished. In the case of new units such information will be required except the portion relating to past production and past level of consumption of input oils.

9.2. The Technical Committee shall satisfy itself, through physical inspection of the plant facility, about the units technical capability for the re-refining of used oils on scientific lines. The minimum general requirements for the used lubricating oils re-refining plant are stipulated.

9.3. There will be no registration without compliance with the requirement for obtaining

ISI Certification Mark scheme relating to engine oils from re-refined base stock.

9.4. After obtaining the Certificate of Registration, it will be obligatory on the part

of the applicant to submit to the Department of Petroleum, at the end of each quarter, details of production. New units will comply with this formality after the commencement of production. The Department of Petroleum may withdraw the Certificate of Registration in the event of noncompliance of this formality. Such action will be taken with the simultaneous advice to the oil companies, DGTD, DC (SSI) and the Director of Industries of the State/ Union Territory in which the re-refining unit is located.

10.0. Guidelines to oil companies on supply of base oils and additives.

10.1. Supply of virgin oil and additives by the oil companies or their subsidiaries will

be made to the re-refining unit only on the basis of Certificate of Registration.

11.0. Guidelines to agencies concerned with supply and disposals of used oils.

11.1. Agencies of Central and State Government as well as public and private sector

industrial enterprises who are bulk consumers of lubricating oils will not, henceforth, dispose of used lubricating oils in auction system or to contractors. Instead, they would make the used lubricating oils available only to the approved and registered re-refiners on the basis of the latters' accreditation with the Ministry of Petroleum. For this purpose,

the Ministry of Petroleum will periodically circulate a list of registered re-refiners.

33

National Bureau of Standards Special Publication 584. Proceedings of Joint Conference

on Measurements and Standards for Recycled Oil /Systems Performance and Durability held at NBS, Gaithersburg, MD, October 23-26, 1979. (Issued Nov. 1980) RE-REFINING WASTE OILS: IMPROVING ACID/CLAY TREATMENT BY USING

ACID SLUDGES AS AN ADDITIONAL FUEL IN CEMENT KILNS

A. L. Roll in and L. Estaque

Ecole Polytechnique of Montreal

P 6079 "A" Montreal, CANADA

An experimental burning of acid sludges was performed in a cement

kiln for a one week period. These acid sludges, resulting from the acid/clay process used in re-refining waste crankcase oils, were used as an additional fuel. In this report a material balance on four toxic elements contained in the acid sludges shows their retention in the produced clinker. The cement produced from the test clinker had properties acceptable for commercial uses. The results of this experimental program indicate that the burning of acid sludge blends is an attractive way to increase the economics of the re-refining process and also prevent

pollution.

1. Re-refining Waste Oils. The Acid/Clay Treatment

E. T. Cutler recently reports in a A.P.I, publication [2] 1 that "re-refining could meet

58 percent of U.S. lube oil needs while conserving oil and preventing pollution". It has been clearly stated by many other scientists [4,6,1] that re-refining appears to be the best way to conserve lube oils. However, among the different industrial processes presently used, the acid/clay treatment is known as the most expensive treatment [5] with the increased costs resulting from the disposal of the residues such as acid sludge and contaminated clay. The purpose of this report is to stress that the use of these acid sludges as an additional fuel burned in a cement kiln can represent an easy way to increase the economics of the process while avoiding pollution.

2. Experimental Program

An experimental program of burning waste oils was done at the St-Lawrence Cement Co. in Mississauga, Ontario in collaboration with the Canadian Environmental Service [1]. It was shown that waste oils could be used as additional fuel in a cement kiln without increasing

the emission of toxic products in the flue gas. In fact the results indicated that the toxic

elements, metals contained in the crankcase oils, were trapped in the produced clinker.

In view of these findings, it appeared interesting to repeat a similar program using

acid sludge blends from the acid/clay treatment as the additional fuel. Since these blends contained the same toxic elements as used oils a similar behavior was forecast and the pro- gram would support oil conservation. Four goals were set for this program:

1) identification of toxic elements in the fuel mixture;

2) identification of toxic elements in the emission gas in the stack;

3) identification of toxic elements in the produced clinker; and

4) determination of some physical properties of the cement. Thus, in April 1977, an industrial testing program was planned with the coordination of

an engineering team from the Chemical Engineering Department of Ecole Polytechnique of Figures in brackets indicate the literature references at the end of this paper.

35
Montreal. Tests were performed at the Canada Cement Lafarge Co. plant at St-Constant,

Quebec, Canada and the program was done with the collaboration of: 1) the Northern Oil Co., who supplied the acid sludge blend; 2) the Canada Cement Lafarge Co., who installed

the combustion system, operated the kiln and sampled and analyzed samples of crude clinker

and cement; 3) the Provincial Environmental Agencies who sampled and analyzed the flue

gas; and 4) the Canadian Environmental Service who financed the program. The analysis of the fuel samples were performed at Ecole Polytechnique of Montreal.

3. Experimental Installations

The experimental installations can be divided into three parts: 1) the combustion

system; 2) the acid sludge blends' circuit; and 3) the sampling outlets.

4. The Combustion System

As shown in figure 1 a temporary circuit was installed near the designated kiln. The

fuel blend was fed to a secondary burner installed just beside the main burner of the kiln which was fed with a Bunker C fuel. The fuel blend was atomized in the flame of the main burner at an approximate ratio of fuel blend to Bunker C of 1 to 20. A storage tank, a filter, two pumps, a flowmeter, high and low pressure alarms, and a safety valve completed

the combustion circuit. More details of the auxiliary burner and the characteristics of the accessories are available elsewere [3].

Storage Tank

P-1: Roper Pump

Helicoidal Gear

60 GPM

P-2: Astral Pump

Model 99 3/8

Figure 1. The combustion circuit.

No modifications were made to the kiln system which operated as in normal production.

The kiln was 490 feet long with a diameter of 15 feet. As shown on figure 2, the crude ore, to which the dust residues recuperated from a dust collector and an electrostatic precipitor

are added, is introduced in the kiln and calcinated. The residence time of the ore in the

36
^i

n

i-It/S

Pr°2 imate

] y ei

' 9ht h °^S - Al> is P reheated by Posing it through the hot clinker and introduced counter currently into the kiln. ^ Sample Outlets

Figure 2. The kiln and the sample outlets.

5. The Acid Sludge Blend Circuit

As shown in figure 3, the used oils are pumped into a flash tower that separates the water and the light ends from the heavier hydrocarbons. This distillate (II) is a first residue that will be used as an ingredient to the fuel blend. The bottoms oil stream is pumped to a reactor into which a sulfuric acid solution is added. Following a lengthy resi- dence time (contact and sedimentation) an acid sludge constituted from heavy hydrocarbons,

additives, sulfuric acid and most of the contaminants is collected. This stream (I) is the second available residue for the fuel blend. Finally used oils (III) and water (IV) are added into the mixing tank to provide good fluid characteristics, to lower the mixture pH and

to ensure homogeneity of the fuel blend. The following properties have been established after tests on blends prepared with these four streams: 20 percent (by volume) of acid sludge, 50 percent of used oils, 20 percent of distillate and 10 percent of additional water. Analyses were performed by the National Research Council of Canada [3].

6. The Sampling Outlets

As shown in figure 2, four sampling outlets were used to collect samples during the testing period from different streams. Prior to the introduction of acid sludge blend into the kiln, samples were collected to establish the kiln operation under "normal operating

conditions". The streams to be sampled and analyzed during the experimental program were: the ore fed into the kiln, the produced clinker, the fuels and the gas leaving the stack.

37
Flash Tower

/I Used [\

H2 S04 A Steam

Oil to Clay Contact

(I) Acid Sludge

(II) Distillate T

H2 0

Figure 3. The acid sludge blending system. The testing period duration was one week; however, several acid sludge blend feed inter- ruptions were caused by pump failure and burner plugging. Coking inside the injection burner circuit (from flashing into the line) was easily overcome by cooling the atomizing circuit with air. The total feeding period of the blend was 90 hours with an average flow rate of 1 GPM as reported in table 1. The feed of crude ore was 93 t/h while 19.5 GPM of Bunker C was used. In spite of the

fact that approximately 5 percent of acid blend was added to the Bunker C as fuel, the Bunker

C's flow rate remained constant during the testing period for a constant feed rate of crude

ore. In total 5529 Gal. of acid sludge blend were fed into the kiln.

7. Results

The results from the analysis of the collected samples and from a material balance of some toxic elements are presented in this section.

7.1. Properties of fuels

Some physical properties and concentrations of elements in the Bunker C and acid sludge blend collected during the experimental program are presented in table 2. It should be noticed that the calorific value of the blend is approximately of 132000 BTU/gal as compared

to 177000 BTU/gal for the Bunker C. The specific gravities of both fuels are similar even though the flash point of the blend is lower than that of the Bunker, being approximately

38
160 °F and 265 °F, respectively. The water content in the blend is approximately of 20 percent and the average concentrations of Pb, Zn, P and Br are respectively of 6000, 1150, 850 and 1100 ppm. Finally, the sulfur concentration represents about 5 percent (by weight)

of the mixture.

7.2. Element identification in the solid samples

The results of the analyses of some elements in the collected solid samples are pre- sented in table 3. One observes that the concentrations of sulfur, phosphorus, zinc and lead are higher in the clinker than in the crude ore plus the added dust collected. These data suggest that the increased concentrations results from the element content in the blend. A confirmation that these elements have been fixed in the clinker can be found in the material balance of each element which gives a retention rate of 93 percent, 89 percent and 87 percent, respectively, for the lead, zinc, phosphorus, and sulfur (see tables 5 to 8). These results

are similar to those obtained in the Mississauga program [1]. Finally the curves representing each element input and output rates and the cumulative input and output are plotted in figures 4 to 6.

Lead Rate (kg/h) Input Output Feed

Bunker Clin Acid Sludge oooo Total

Cumulative Lead Input •— Cumulative Lead Output

oooooooo

~tlY1 1 May 1 Figure 4. Lead rate and cumulative lead input and output. Only an average retention of 12 percent of the bromine that enters the kiln is found in the clinker suggesting that the bromine appears as potassium bromide in the precipitator

system. This suggestion, due to Berry [1] is corroborated by the data of table 9. 7.3. Analysis of flue gas The analyses of the samples of stack gas indicate no increase in the concentration of the toxic elements during the testing period (table 4). The samples collected on April 22nd

39
correspond to the operation of the kiln prior to the experiment and the results of the analysis of those samples can be used for comparison. It is noted that on April 27th the concen- tration of the four toxic elements were very high. This is explained by a poor performance

of the electrostatic precipitator on that day. In spite of these production problems, the toxic elements' concentration in the flue gas were lower than the Environmental Protection Agency's specifications.

April 24 May 1 Figure 5. Cumulative lead, zinc and bromine input and output.

7.4. Energy balance

An accurate energy balance on operating cement kiln is very difficult to make because of lack of data on the energy losses. For that reason, and also because of fluctuations in some

of the operating variables, it was impossible to close the energy balance. The energy input

of the acid sludge blend was small compared to the combustion of the Bunker C. 7.5. Cement properties

The clinker produced during the program was used to make cement samples which were analyzed to insure properties acceptable for commerical uses. The results of the analysis performed by Canada Cement Lafarge Co. indicated that the setting times were faster than those of samples of cement produced prior to the experiment. However, these times were within acceptable limits. The compressive strength was better than that of the cement pro- duced prior to the experimental period. All other properties fell into the acceptable range

set by the company.

40
Figure 6. Cumulative sulfur and phosphorous input and output.

8. Conclusion

The primary conclusions of this experimental program is that the burning of an acid

sludge (from an acid/clay treatment of used oils) in a cement kiln is an attractive way to increase the viability of the re-refining process and to prevent pollution. It was found that the toxic elements contained in the fuel blend are trapped in the clinker with no sig- nificant increase of toxic elements in the flue gas. Finally, the cement produced with the clinker obtained during the testing period has properties acceptable for commercial uses. Unfortunately, this trial did not allow us to make an energy balance hence a detailed

program should be considered to evaluate the real calorific contribution of the acid sludge

blend. The accumulation of the bromide in the dust collector circuit should be analyzed in more detail. Finally, a study of the best acid sludge mixture should be undertaken to opti- mize the process.

41
TOTAL

BY

DAY

I

Clinker (t)

(m 3)

1444.81444^8

444

1418.4 1473.6 1444.8

1428.0

455

1392.0

465

1428.0

471

1452.0

486

1435.2

469

1

Acid

sludge

blend

(gal) 0 0 0 0 0 km

1 1 III mil

Feed

(t/h)

2256.0 2258.4 2215.2 2301.6 2258.4 2229.6 2174.4 2232.0 2270.4 2244.0

Air

(stack) (m

/mn) III!

CI

inker (t/h) 60.2 60.2 59.1 61.4 60.2 59.5 58.0 59.5 60. 5

59.9 o

r-i

IX> i

!

1

il

= s

o

Bunker

(gal/min) 19.

46.

19.34°

20.00

18.58.19.34° 19.41°

18.49 19.72 19.66 19. 80 s

s

-O 0°rH rO did

92.9°

90.6 94.6 93.5

Operation

with

acid

sludge

blend(h) 0 0 0 0 0 8.66

22.75 21.00 24.00 15.75 o

DATE 21-

4-77

22-

4-77

23-

4-77

24-

4-77

25-

4-77 £££££

ttm

R

i

42
Table 2. Properties of fuels. BUNKER ACID SLUDGE BLEND

Date 26-4

(20h) 27-4(7h30) 28-4

(14h) 29-4

(2h30) 30-4

(14h)

Pb (ppm) (45) 6060 - 6400 5620 - 6100 5665 - 5800 5950

Zn (ppm) 47 1150 1130 1160 1060 1290

P (ppm) 2.5 1209 744 79 9 908 803

Br

(ppm) 8 1040 1080 103i 1070 1170

S (%) 2.97 - 4.2 5.6 4.6 6.2 4.9 4.7

H

20 (%) .05 20 19 19. 5 18 19. 5 H

2 S04

(%) .05 6. 0 5. 63 5. 60 4. 58 5.09 Calorific Power

(BTU/gal.) 177580 129613 134411 134681 129466 134078 Specific

Qrs v i ty .967 .961 .960 .963 .957 Flash point

(°F) 265 170 140 175 155 170

43

Table 4. Analysis of gas in the stack.

SAMPLING DATE

April 22nd

AVERAGE FLOW

m

3/mn

1850.93

TEMPERATURE

°C

327

CONTENT

Pb mg/m3 .116

Zn mg/m3 .116

Br mg/m3 .071P mg/m3 .625

P

P. P.m. 81

SO

P. P.m.

- April 26th 1896. 96 342 .145 .172 .121 .906 65 April 27th

(8h-16h)

April 27th (16h-24h)

1901.61

1977.53

319 .198 .106 .119 .56 53 .2

319 1.44 .682 .188 5.65 16 .9

April 28th

(8h-16h) 1942.41 319

roo SMAL L SAMPLES

16 .5

April 28th

(16h-24h) 1984.20 324 .518

a .085a .002

a .045

a 40 7.6

April 29th 2025.54 320 00 SMAL . SAMPLES

rL

April 30th 1957.36 317 1 1 TOO SMALL SAMPLES

I i

Without the sample from the filter in the sampling train. Table 5. Mass balance on lead. Input (Ib/D) Output (Ib/D)

Date Feed Bunker Blend Total Clinker Stack Total Retention

(%)

| 26-4-77 142.56 12.2 30.2 185 1 159.8 .34 160.1 86 27-4-77 134.9 11.5 73.7 220 1 178.1 .50 178.6 81 28-4-77 138.2 12.2 68.5 219 0 194.2 194.2 88 29-4-77 140.6 12.2 82.3 235 1 223.7 223.7 95 30-4-77 134.6 12.5 52.9 200 0 232.6 232.6 116 TOTAL(lb) 690.9 60.9 307.7 1059 2 988.4 989.2 93

45
Table 6. Mass balance on zinc. Input (lb/D) Output (lb/D) Date Bunker Total CI inker Stack Total Retention

(%) 26-4-77 115 9 5. 7 134. 3 128.4 .7 128.4 95 27-4-77 121. 7 12.

148. 5 130.

1.

131.8 89 28-4-77 128.2 13.0 14. 05 153. 3 131 3 131. 3 85 29-4-77 122.6 12.7 14.6 149.95 133.4 133.4 89 30-4-77 121.2 13.0 11.7 145.95 132.0 132.0 90 TOTAL(lb) 609.6 63.4 60.95 733.95 655.9 657.6 89

Table 7. Mass balance on phosphorus. Input (lb/D) Output (lb/D) Date Feed Bunker Blend Total Clinker Stack Total Retention Prior to Experimet 1184.7 1502.6 26-4-77

2407.9 .67 6.0 2914.6

2170.56 5.28 2175.84 90

27-4-77

2435.3 .62 9.8 2445.7 2115.8 3.4 2119.2 86

28-4-77

2232 .67 9.66 2242.2 1970.64 1970.64 88

29-4-77

2179.7 .67 12.48 2182.8

2032.8 2032.8 93

30-4-77

2154. 24 .69 7.32 2162.3

1865.7 1865.7 86

TOTAL(lb) 11409.1 3.32 11447.6 4364.

10164.8 89

46
Table 8. Mass balance on sulfur. INPUT (lb/D) OUTPUT (lb/D) Retention

Date Feed Bunker Blend Total Clinker Stack Total (%) Prior to Experiment

26- 4-77

27- 4-77

28- 4-77

29- 4-77

30- 4-77

13333

13704

13940

13778

7990 8019

8147

8122

8180

0 283

747

663 484

21635

22599 22728

22442

20524

15137

20849 19166

22676

32.3

-

20524

15137

20881

19166 22676

91

7086

9284 101

Total Experiment 67888 40107 2791 110786 96202 96239

Average

Experiment 13578 8021 558 22157 19240 19248 87

Table 9. Mass balance on bromine.

INPUT (lb/D) OUTPUT (lb/D)

f

1 Retention

; Date Feed Bunker Blend > Total Clinker Stack Total (%) Prior To Experiment 2.26 2.16 0 4.42 .41 26-4-77 2.66 2.16 5.20 10.03 .29 .72 1.01 10.1 27-4-77 2.62 2.06 14.19 18.88 .55 .72 1.27 6.7 28-4-77 2.23 2.18 12.49 16.91 1.44 1.99 11.8

29-4-77 2.28 2.18 15.53 19.99 1.44 1.44 7.2 30-4-77 1.80 2.21 9.81 13.82 4.01 4.01 29.0

Total Experiment 11.59 10.79 57.23 79.53 7.73 9.72 Average Experiment 2.32 2.16 11.44 15.91 1.55 1.94 12.1

47
References

[1] Berry, E. E. , McDonald, L. P., and Skinner, D. J., Experimental burning of waste oil as a fuel in cement manufacture, Report EPS-4-WP-75-1, Environment Canada (1975).

[2] Cutler, E. T. , Conserve lube oil: re-refine, Hydrocarbon Processing, 86 (May 1976).

[3] Estaque, L. and Rollin, A. L. , Essai de combustion dans un four a ciment d'un melange constitue de residus du procede de regeneration des huiles usagees, Technical Report

CDT, Ecole Polytechnique de Montreal, 335 (November 1977).

[4] Skinner, D. J., Preliminary review of used lubricating oils in Canada, Report EPS- 3-WP-74-4, Environment Canada (1974).

[5] Weinstein, N. J. , Re-refining schemes compared, Hydrocarbon Processing, 74, (December

1974).

[6] Whisman, M. L. and et al., Re-refining makes quality oils, Hydrocarbon Processing, 41 (October 1978).

[7] Cukor, Peter, Waste oil recycling study, Teknekron Inc., Technical Report for the Ontario Ministry of Energy (March 1976).

48
Session 2 ENGINE OIL EVALUATION

49

National Bureau of Standards Special Publication 584. Proceedings of Joint Conference

on Measurements and Standards for Recycled Oil /Systems Performance and Durability held at

NBS, Gaithersburg, MD, October 23-26, 1979. (Issued Nov. 1980)

STATUS OF THE MIL-L-46152A ENGINE OIL SPECIFICATION

T. Bowen

U.S. Army, MERADCOM

Mobility Equipment Research and Development

Ft. Belvoir, VA 22060 Over the past several years, the Department of Defense has placed considerable emphasis

on the revision of military petroleum product specifications to allow the use of recycled or re-refined materials. Although this effort is not complete, significant advances have been

made. One such advance has been with the MIL-L-46152 lubricating oil specification under

which engine oil is procured for use in administrative vehicles. A draft revision of the specification allowing the use of re-refined materials has been prepared and forwarded to the

U.S. Army Materials and Mechanics Research Center for editorial review and issuance. Also as

an interim measure to expedite the procurement of these lubricants a purchase description,

ME-101, covering engine oil as defined by the draft specification was issued on the 15th of October 1979. Today, I will briefly describe the requirements established by these documents. Before entering this discussion, let me clarify one point. The draft specification has a qualification requirement which is not included in the purchase description perse. However,

the purchase description does require lubricant approval; the process for which is the same as that required for qualification under the specification. In other words, both documents

require prior testing and review before lubricants are purchased. Prpducts which are approved

for purchase under the purchase description will be qualified products when the specification

is issued.

As with previous military engine oil specifications or purchase descriptions, the MIL-L-46152A and ME-101 documents are based on lubricant performance. As such only minimal constraints are placed on lubricant composition and properties prior to qualification or approval. Materials to be used in formulating the lubricant are defined in general terms as shown by table 1. Note that the base stock may consist of a virgin, re-refined or a combination virgin-re-refined product. In regard to property requirements illustrated in table 2, viscosity and viscosity index are used to define lubricant grade and maximum pour and minimum flash point values are established to provide a general control of low- temperature

handling and product volitality, respectively. One new requirement, a maximum 0.14 mass percent phosphorus limit, is included because of the harmful affects on emission control systems associated with phosphorus containing additives. Table 1. Material requirements before qualification/approval.

o Base stocks: petroleum, synthetic, or combination: virgin

re-refined, or combination.

o Additives: detergents, dispersants, oxidation inhibitors, etc.

51
Table 2. Finished oil property requirements before qualification/approval.

Property 10W 30 5W-20 10W- 30 20W-40 Viscosity @ 100 °C, cSt min max

5.6 <7.49.3 <12.55.6 <9.39.3 <12.5

12.5 <16.3 Viscosity @ -18 °C, cP min

max 1250 <2500 <1250

1250 <25002500

< 10000 Viscosity Index (min) -- 75 -- -- "

Pour Point, °C (max) -32 -18 -40 -32 -23 Stable Pour Point, °C (max) -32 -40 -32 -23 Flash Point, °C (min) 205 220 200 205 215 Phosphorus, %M (max) 0.14 0.14 0.14 0.14 0.14

Table 3. Engine test requirements. Test

L-38

Brg. Wt. Loss, Mg (max.)

Seq. IID

Avg. Rus (min) 8.5 Lifter Sticking None

Seq. HID

Vise. Inc. @ 40 °C, 40 h, % (max.) 375 Piston Varnish (min) 9.1

Oil Land Deposit (min) 4.0

Sludge (min) 9.2 Ring Sticking None Scuffing & Wear @ 64 h Cam or Lifter Scuffing None

Cam + Lifter Wear urn Avg. 102

Max. 254

Seq. V-C/V-D

Avg. Eng. Sludge (min) 9.0/9.2

Avg. Eng. Varnish (min) 8.1/6.4

Piston Skirt Varnish (min) 8.0/6.3

Oil Screen & Ring Clogging, % (max.) 5/10

Comp. Ring Sticking None/None

Cam Wear, urn Avg. —/51

Max. -/102

Cat. 1H2

Top Groove Filling, % (max.) 45

Total Weighted Deposit, (max.) 140

Requirement

40

52
The key to both the specification and purchase description is lubricant performance

as defined by a series of engine dynamometer tests. Requirements for these tests are summarized by table 3. Note that requirements are presented for both the sequence V-C

and recently approved sequence V-D procedure. It is envisional that use of the sequence V-D procedure will be implemented as soon as possible. These requirements are the same as established for API performance classification SE--CC. After qualification or approval, the latitude allowed in formulation is removed. As shown by table 4, the manufacturer is restricted to the same base stock--additi ve combination

as was used for the qualification or approval sample. Tolerances, more restrictive than the prior general requirements, are established for both the chemical and physical properties of the lubricant. In addition, the MIL-L-46152A specification provides for annual monitoring and sampling of base stock materials as shown by table 5. It is noted that tolerances require- ments are not currently assigned to the base stock properties. However, significant variation

from the initial characteristics would require an explanation and could possibly necessitate

partial or complete retesting of a product. Table 4. Material and tolerance requirements after qualification/approval.

Material

o Base Stock: same source and refining treatment as used in qualification/

approval sample.

o Additive: identical as used in the qualification/approval sample. Finished Oil Tolerances

o Gravity, °API

o Flash, Finished Oil °C

o Viscosity

o Viscosity Index

o Pour Point, °C

o Stable Pour Point, °C

o Ramsbottom Carbon, %

o Sulfated Ash, %

o Elemental Constituents

Table 5. Base stock properties. Viscosity

At 100 °C, centi stokes

At 40 °C, centi stokes Viscosity Index Gravity, °API Pour Point, °C Carbon Residue, %

Sulfated Ash, %

Total Acid Number Saponification Number

Elemental Content, Mass %

Nitrogen

Chlorine

Sulfur

Color Boiling Point Distribution, °C

@ 1, 5, 10, 50, and 90% Point

53
Although the specific date of issue for MIL-L-46152A is not known, the specification

should be available in the near future. As an interim measure the ME-101 Purchase description will allow the procurement of the quality level lubricant as defined by the proposed specification.

54
National Bureau of Standards Special Publication 584. Proceedings of Joint Conference

on Measurements and Standards for Recycled Oi 1 /Systems Performance and Durability held at

NBS, Gaithersburg, MD, October 23-26, 1979. (Issued Nov. 1980)

FIELD TEST OF RE-REFINED AUTOMOTIVE ENGINE OIL

IN RCMP VEHICLES

J. Armstrong

Environment Canada

351 St. Joseph Boulevard

Hull, Quebec K1A 1C8 CANADA

1. Introduction

First, I would like to thank the organizers of this conference for inviting Environment

Canada to participate in it. I will be describing the re-refined oil testing program which we

are presently conducting, in conjunction with a number of other agencies. The first phase of this program is now approximately 50 percent complete, and involves a comparison and evaluation

under selected field operating conditions, of the performance characteristics of a virgin base stock reference oil and a re-refined base stock test oil. I will be presenting some of the

data we have obtained to date, along with some of the observations which can be made with this

data.

2. Description of Test

The field test portion of the program was started in early March of this year, and is expected to run until December or January. Eight new, identically-equipped patrol cars were

made available for use in the program by the Royal Canadian Mounted Police Force. These cars

are 1979 models, Chevrolet Bel-Air sedans equipped with police-duty 305 cu in V-8 engines and automatic transmissions. They are all based in Ottawa and all experience essentially the same city-driving type patrol service. They operate on a continuous basis, 24 h/day, 7 days a week, and accumulate between eight to ten thousand kilometers per month. Barring accidents or other unforeseen circumstances, the test program will continue until the cars reach their

normal fleet mileage of 100 000 km. At this time, all the engines will be disassembled and examined and rated for sludge and varnish accumulation. Because we did not premeasure the engines, wear comparisons will be based primarily on visual examination.

The reference oil being used is a commercially available, fully-qualified, API SE-CC multigrade 20W40 oil prepared from virgin base stocks. The additive formulation used in the reference oil was used at the same treatment level with acid-clay re-refined base oil to prepare the test oil. This approach was taken to allow us to isolate, as much as is possible,

the performance characteristics of the base oils only.

3. Physical and Chemical Properties Most of the physical and chemical properties of the base and finished oils have been determined, largely through the efforts of the Fuels and Lubricants Laboratory of the National Research Council, and I will discuss a few of them today. Some of the physical properties of the two base oils used for formulation of the finished

oils are shown in table 1. Both oils are approximately an SAE 20 grade. I should point out

here that the virgin base stock is a blend of approximately equal parts of SAE 10 and SAE 30 grade oil. While the specific gravity and viscosities of the virgin and re-refined oils are quite similar, the VI of the re-refined oil is somewhat higher than the virgin oil, and the flash point of the re-refined oil is about 15 °F lower than that of the virgin oil. As would

be expected, there was a color difference between the two oils.

55
Table 1. Physical properties of base oils. Virgin Re- refined

Base Stock Base Stock

A.P.I. Gravity 29.7 29.6

Uicrn<;itu 0 1 00 °C 7.30 cSt 7.51 cSt Viscosity @ 40 °C 53.43 cSt 52.62 cSt Viscosity Index 95 104.5 Flash Point 435 °F 420 °F Color <1.0 <3.0 Determination of the boiling point distribution showed a slight difference between the two oils. Plotting these figures (fig. 1) shows the boiling range of the re-refined base oil (the dotted line on the figure) to be about 20 °F lower than the virgin oil boiling range. This is probably due to the presence of light ends in the re- refined oil, and this may be one

of the reasons for a slightly higher oil consumption rate in the cars using the re-refined

test oil

.

1200

500 ' 1 1 1 ' 1 0 20 40 60 80 100 Percent Distilled Virgin Base Oil Re-refined Base Oil

Figure 1. Boiling point distribution.
One of the reasons we had for selecting the re-refiner we did, was that the National Research Council had previously examined samples of his re-refined oil, and therefore had a reasonably good idea of what the oil would be like. While I believe the subject of base stock consistency is being addressed later in the conference, I have prepared the following table

(table 2) to show that the re-refined base oil we are using is representative of the re- refiner's production. The first column of figures in the table are the average values from

ten samples of re-refined oil produced by the re-refiner during the period 1968 to 1978. As can be seen, the properties of our test oil are quite similar to the previous sample averages,

and I think it is fairly safe to say that we are using "normal" production quality oil. Table 2. Re-refined base stock consistency. Samples 1968-1978

Test Oil Base Stock

A.P.I. Gravity 29.6 29.6 Viscosity @ 100 °C 7.50 cSt 7.51 cSt Viscosity @ 40 °C 54.90 cSt 52.62 cSt Viscosity Index 100.25 104.5

Flash Point 418 °F 420 °F Color <2.0 - 3.5 <3.0

Some properties of the finished oils are shown in the next table (table 3). The oils were formulated to SAE 20W40 grade, this being a formulation which was suitable for year-round

operation, and one that would allow us to use only re-refined base stock for the test oil. As was the case with the base oils, the two finished oils are reasonably similar. Total Acid

Number shows two separate determinations for each oil. Table 3. Properties of finished oils. Virgin

Oil Re- refinedOil SAE Grade 20W40 20W40

A.P.I. Gravity 27.9 28.5 Viscosity Index 127.5 132.5

Flash Point 445 °F 440 °F

T.A.N. 2.24/2.78 2.5/2.64

T.B.N. 5.71 5.74

4. Field Test Results to Date

As I said earlier, the field test portion of the program is approximately 50 percent

(table 4). We have four patrol cars operating on each oil. Over 168 000 km (about 105 000

miles) have been accumulated on the virgin oil, and over 150 000 km (approximately 94 000

miles) on the re-refined oil. All cars are following the normal maintenance schedules and procedures practiced by the RCMP, including oil and filter changes every 5000 km. However, be- cause the cars are operating on a continuous basis, their availability for servicing is af- fected, and we are seeing oil changes occurring anywhere from about 2500 km to about 10 000 km, with the majority occurring around the 5000 km mark. For some reason, presumably chance, the vehicles using the re-refined oil are so far exhibiting about a 600 km longer average oil change interval than the cars using the virgin oil.

57
Table 4. Field test 50 percent complete.

No. of Test Vehicles

Total Test Mileage

No. of Oil Changes

Avg. Oil Change Interval

Virgin

Oil

168 400 km

33 5128 km

Re-refined

Oil

154 100 km

27 5720 km

We have been monitoring relative engine condition and used oil performance characteristics by analyzing samples of used oil taken at each oil change. These samples are being analyzed for metals, viscosity, and fuel, glycol, and water content by a private

laboratory. The Fuels and Lubricants Laboratory of the National Research Council have been providing the physical and chemical analyses of the used oil, including infrared analysis. The averages of some of these properties are shown in table 5. Table 5. Used oil properties.

Average Top-Up Rate Average Oil Age Average Iron Content Viscosity Increase @ 100 °F Viscosity Increase @ 210 °F Degree of Oxidation

Virgin

Oil 0.21 Liter 1000 km 979 km/L

31 PPM 15.7 cSt

0.6 cSt

9.5 ABS

CM

Re- refined

Oil 0.25 Liter

1000 km 1006 km/L

37 PPM

29.6 cSt

1.76 cSt

17.3 ABS

CM

As I mentioned earlier, the average top-up rate for the re-refined oil (0.25 liter/1000 km)

is somewhat higher than the virgin oil top-up rate of 0.21 liter/1000 km. However, because of the longer average oil change interval being experienced by the cars using the re-refined oil, the calculated average oil age is about the same--1006 km/liter and 979 km/liter for the group of cars using virgin oil. The average oil age at each oil change

is calculated by dividing the number of kilometers driven since the last oil change by the

total quantity of oil added to the crankcase, that is, the 4.5 liters initial charge plus the amount of top-up oil added during the period. Use of this figure instead of distance traveled between oil changes as an independent variable during analyses helps to account

for the variations in top-up rate and length of oil change intervals.

For the remaining properties shown— iron content, viscosity increase, and degree of oxidation of the used oils--the values obtained for the re-refined used oil are consistently

higher than those measured for the virgin oil. A fair bit of information about the comparative behavior of the two oils can be obtained

from looking at graphs of the used oil properties plotted against average oil age. The next

few slides I will show are the graphs of iron content, viscosity increases at 100 °F and

210 °F, and the degree of oxidation measured for the used oil samples.

58
The first pair of figures show the iron content of the used oil. Interestingly, the slope of the best-fit line for the cars using virgin oil (fig. 2) is about twice as steep as the slope of the line obtained for the re-refined oil (fig. 3). As a point of interest, one of the vehicles using re-refined oil was in an accident about a week after the field test

started, and while no front-end or engine damage occurred, it sat idle for about six weeks while repairs were being made. Analysis of the used oil from the first oil change after the accident resulted in the 95 ppm iron concentration outlier on the graph. The iron concen- tration of the next oil sample obtained from this vehicle was 41 ppm. The next four figures show the behavior of used oil viscosity with respect to oil age. The behavior of each oil is similar, with the best fit lines for each having essentially the same slopes but different intercepts. This was observed at both 100 °F and 210 °F. The viscosity increases observed in the virgin oil at 100 °F (fig. 4) are about 15 cSt less than the viscosity increases measured for the re-refined oil (fig. 5). Similarly at 210 °F, the viscosity increases observed in the virgin oil (fig. 6) are about 1.0 - 1.5 cSt less than those observed for the re-refined oil (fig. 7). The graphs of the oxidation products present in the used oil do not indicate the parallel behavior seen with the viscosity increases. The virgin oil (fig. 8) shows a considerably less rapid increase in oxidation products with oil age than does the re-refined oil (fig. 9). In an attempt to provide a somewhat more thorough analysis of the used oil data, we subjected the previous four properties plus copper concentration data to a more sophisticated

linear regression analysis, using average oil age, vehicle odometer reading, and oil type

(i.e., virgin or re-refined) as independent variables. Keeping in mind the limitations on validity of results obtained from this type of analysis on the relatively small amount of data we have, the following results were obtained at statistically significant levels:

1) In the analysis of iron concentration, oil type was not a significant contributor

to the measured responses. Average oil age was by far the most significant

independent variable.

2) In the analysis of copper concentration, total engine mileage (i.e., odometer

reading) was the most important contributor, with both kilometer and kilometer-squared terms being more significant contributors by an order of magnitude over the other variables.

3) Both average oil age and oil type, in that order, exhibited significant

effects on the measured viscosity increases in the used oil samples, both

at 100 °F and at 210 °F. 4) Analysis of oxidation products indicated that all three independent variables—average oil age, oil type, and total mileage accumulation-- were significant contributors to the measured responses.

4. Conclusions

To conclude, I would like to repeat that the field test has been designed to isolate the performance characteristics of the virgin and re-refined base oils being studied. The con- ditions selected for the test are those normally experienced by RCMP vehicles in similar

service. We have attempted to ensure that all test and reference vehicles are subjected to

as equal treatment as possible, in both driving conditions and maintenance schedules. The primary conclusion that can be made with the data obtained to date is that there are statistically significant differences occurring in certain measured properties of used crankcase oil from the two test groups of vehicles. These differences are no doubt attributable,

at least in part, to performance differences between the two finished oils, but other factors

such as the observed differences in length of oil change interval and top-up requirements are also contributing to the responses being measured. Given the methods by which we defined and chose the test and reference oils, it might be expected that differences in performance characteristics would be observed, and also that the reference oil might exhibit "better" performance characteristics than the test oil. However,

59
we will not know the final magnitudes of any differences between the oils until the field test period is completed, and the real significance of these differences, in terms of their effect

on the engines, cannot be determined until the engine examinations have been completed.

a/Virgin Oil US©

100 m

• • •

• • • • •

100 1000 Average Oil Age, KM/Litre 1500

Figure 2. Iron concentration in crankcase drain samples.

60
b/Re-refined Oil 150

100

50 x

x x X

X

X x

x

X xx

*x

x xx xX x x

X J L

500 1000 1500 Average Oil Age, KM/Litre

Figure 3. Iron concentration in crankcase drain samples.

61
a/Virgin Oil

• • • • • •

500 1000 Average Oil Age, KM/Litre 1500

Figure 4. Viscosity increase at 100 °F.

62
b/Re-refined Oil

X

X

X X*

X

X x

x

X

500 1000 Average Oil Age, KM/Litre 1500

Figure 5. Viscosity increase at 100 °F.

63
a/Virgin Oil

3..0

2 0

1 0

—1.0

G

On • • • • 8 0.0 \% • *

1000 Average Oil Age, KM/Litre 1500

Figure 6. Viscosity increase at 210 °F - virgin oil.

64
b/Re-refined Oil 5.0 r

4.0 -

X

X X

X

X

X

X

X X x

XX

500 1000 1500 Average Oil Age, KM/Litre

Figure 7. Viscosity increase at 210 °F - re-refined oil.

65
a/Virgin Oil

E

e/) cn 20.0 h

<

o CO

_L

1000 Average Oil Age, KM/Litre 1500

Figure 8. Oxidation products in used oil - virgin oil.

66
b/Re-refined Oil

<

40.0 r

30.0 -

20.0

10.0 - X

X X * X,

0.0500

I 1000 Average Oil Age, KM/Litre 1500

Figure 9. Oxidation products in used oil - re-refined oil.

67

National Bureau of Standards Special Publication 584. Proceedings of Joint Conference

on Measurements and Standards for Recycled Oil /Systems Performance and Durability held at NBS, Gaithersburg, MD, October 23-26, 1979. (Issued Nov. 1980) PROP RE-REFINED OIL ENGINE TEST PERFORMANCE

R. E. Linnard Phillips Petroleum Company

429 TRW Building

Bartlesville, OK 74004

At the 1977 NBS-sponsored Conference on Recycled Oils, I reported to this group on the Phillips Re-refined Oil Process (we call it PROP 1 ). At that time engineering and fabrica- tion of the first PROP oil re-refining plant were just getting underway. While we were not then in a position to disclose details about the process (as we have subsequently done on NPRA paper AM-79-21) I did make a point of describing Phillips' intent to demonstrate

the efficacy of the process in terms of the quality of its product as meeting industry recognized standards of engine test performance. Specifically, we indicated our intent to put PROP re-refined motor oils through the same independent laboratory engine tests as are commonly undertaken with virgin oils to show compliance with the approval requirements of MIL-L-46152 and to give credible support

to claims of API Service SE/CC quality.

In the intervening two years, we have not deviated from our initial approach for demon- strating product quality. Recognizing the lack of meaningful alternatives, ASTM engine tests conducted by independent laboratories continue to be used as attestations of the high quality

of PROP plant-produced re-refined base oils. Using conventional, commercially-available

nonproprietary (to Phillips) additive treatments, engine test programs have successfully

demonstrated PROP oils' compliance with the performance requirements of MIL-L-46152A and

API Services SE/CC.

In the brief time allotted, I will report on our engine testing experience with PROP re- refined oils as produced in a full-scale 2 MM GPY PROP plant operating with Buyer-collected

used oil feedstocks. I will also comment on the status of the first two PROP plants, one built for the State of North Carolina and the other for Mohawk Oil Company, Ltd., Vancouver

B. C. , Canada. Before getting into the details of the testing programs, I want to elaborate briefly

on Phillips concept of contractually demonstrating product quality to Buyer's of PROP plants. Technically credible proof of quality is essential to industry and government acceptance

of lubricants blended with re-refined oils. From this base, public acceptance will evolve providing undeserved labeling requirements are lifted by FTC. Simplistically-speaking, this requires demonstration of re-refined base oil equivalency

to virgin oil blending stocks, quality-wise. For the PROP program, we are utilizing the SAE/ ASTM/API service definitions and engine test criteria to demonstrate the additive-treated

re-refined oil's equivalent or "passing" performance. With the use of widely available, com- mercial additive packages, we view this not only as adequate verification of base oil quality,

but also as being in the best interests of re-refiners and oil compounders who desire to employ re-refined base stocks in their motor oil blends. Contractually, we are prepared to carry out such tests for each Buyer of PROP plants. Once this is successfully done, the Buyer then has the responsibility for utilizing PROP base oils in his development of a variety of specific products to meet his marketing needs. This concept is consistent with that Phillips has followed during the 30 years of operation

of its solvent extraction lube oil refinery in Kansas City--namely to produce high quality

paraffinic base stocks as the starting point for blending a wide range of additive-treated

automotive and commercial oils. Registered trademark.

69
Phillips plans to continue with this format for those Buyers of PROP plants desiring this degree of quality assurance until such time as NBS is successful in coming up with the equiv- alency tests, as required by the EPCA Act of 1975 (PL 94-103). Hopefully, these will be less complex and less costly, but I doubt that anyone here believes this to be less of a challenge

to NBS now than when discussed at the first of these conferences. Nonetheless, with ASTM now deeply involved in this effort, and with the Department of Defense' amendment to MIL-L-46152

('A' revision) recognizing the potential equivalency of re-refined and virgin base oils, we optimistically believe real progress will be forthcoming.

Let us turn now from prognostications to facts. PROP base oils used in the blending of SE/CC motor oils for independent laboratory engine testing programs were produced in the 2 MM GPY plant built for North Carolina. The production runs were made with plant operation at its temporary site at the Phillips Research Center. (PROP oil, for the first two testing programs

I will discuss, involved plant runs with used oil feedstock collected by the State of North Carolina.) The third involved base oil recovered from waste oil collected by Mohawk Oil Company and supplied as feedstock representative of their half-million gallon storage in the Vancouver area. Data pertaining to the oils tested and the results of their SE/CC engine tests performed

by outside certified laboratories are shown in the next several tables (table 1). Programs conducted with North Carolina PROP oil contain two different additive treatments. Program A utilized a "Universal" additive treatment and a 20 cSt @ 100 °C viscosity adjusting stock to bring the blended oil viscosity to the mid-range of the SAE 30 grade. Program B was less conservative, utilizing a competitive-cost additive treatment recommended for SE/CC per- formance. Viscosity adjusting stock was not used in the Program B oil blend; hence its viscosity was within but near the lower limit of the SAE 30 grade. Table 1. Prop oils for engine testing programs A & B. Feedstock Source: North Carolina Used Oil Collections

Processing: 2 MM GPY PROP plant Motor Oil Grade: SAE 30 Re-refined Neutral, %

Viscosity Adjusting Stock, %

Detergent-Inhibitor, %

Pour Point Depressant, %

Physical Properties: Flash Point, °C Viscosity, cSt @ 40 °C cSt @ 100 °C Viscosity Index

TBN Sulfated Ash, %

Zinc, %

Program A 78.9

9.7 11.3 (Univ.)

0.1

216 104.1 11.58

108

3.9

1.00 0.14

Program B 92.2

7.7 (SE/CC)

0.1

75.7 9.89

111

6.9 1.08 0.15

Sequence I ID , HID, Caterpillar 1-H2 and CLR L-38 engine tests have been successfully completed in both programs (tables 2 and 3). Sequence VC data complete Program A, confirming

this oil's SE/CC and MIL-L-46152A. A Sequence VD test is scheduled for Program B (tables 4 and 5) with all other test data indicating its SE/CC performance. Contingent upon passing Sequence VD results, this program will be presented to the SAE's Lubricants Review Institute

for Review Board approval as meeting the MIL-L-46152A specification.

70
Table 2. Engine test results prop oil - program A. ENGINE TEST

Ratings:

Avg. Rust

Avg. Sludge

Avg. Piston Varnish

Avg. Engine Varnish Ring/Land Varnish

Oil Ring Clogging

Oil Screen Clogging

Ring Sticking

Lifter Sticking

Avg. Cam/Lifter Wear, in Max. Cam/Lifter Wear, in Cam/Lifter Scuffing Viscosity Incr. @ 40 h %

Viscosity Incr. @ 64 h %

Oil Consumption, qts

SEQ. IIP

Overall Rating

SEQ. HID

9.6

9.4

None

None 0.0038

0.0051

None

59

923.31

Engine test results prop oil - program A. Cat. 1-H2

SEQ. VC

9.5

8.0 8.5

None

None

None

Fed. Test Method

Ratings: Top Groove Carbon, % Weighted Total Deposits Bearing Weight Loss, mg Piston Varnish OVERALL RATING

ENGINE TEST

Ratings:

Avg. Rust

Avg. Sludge

Avg. Piston Varnish

Avg. Engine Varnish

Ring/Land Varnish

Oil Ring Clogging

Oil Screen Clogging

Ring Sticking

Lifter Sticking

Avg. Cam/Lifter Wear, in Max. Cam/Lifter Wear, in Cam/Lifter Scuffing Viscosity Incr. @ 40 h %

Viscosity Incr. @ 64 h %

Oil Consumption, qts. OVERALL RATING

3 139.3

PASS Engine test results prop oil SEQ. IIP 8.7

34.1

9.6

program B. SEQ. HIP

9.5 9.2

None

None 0.0032 0.0058

None

53 1703.31

SEQ. VP

IN PROGRESS

71
Table 5. Engine test results prop oil - program B. Engine Test

Fed. Test Method

Ratings: Top Groove Carbon, %

Weighted Total Deposits

Bearing Weight Loss, mg Piston Varnish

0 100.9

28.9

9.6 OVERALL RATING Program C results, as shown in tables 6, 7, and 8 pertain to a similar demonstration of PROP oil quality as re-refined from Mohawk-supplied Canadian waste oil feedstock. In this instance, the plant-produced 300 neutral stock (62 cSt @ 40 °C) was fractioned into two blending stocks--a 150 neutral and 700 neutral. This fractionation simulates the Buyer's intention to fractionate the product in his PROP plant operations. Also as an accommodation

to this Buyer's specific interests, Sequence tests and the L-38 test were run with an SAE 10W-30 grade for SE performance, and the Caterpillar 1-H2 test with the SAE 30 grade. Table 6. Prop oil for engine testing program C. Feedstock Source: Mohawk Oil Co. Ltd. Used Oil Collections

Processing: 2 MM GPY PROP plant

Re-refined Light Neutral, %

Re-refined Heavy Neutral, % Detergent-Inhibitor, %

Viscosity Index Improver

Pour Depressant Solution

Physical Properties:

Flash Point, °C Viscosity, cSt @ 40 °C cSt @ 100 °C Viscosity Index

TBN Sulfated Ash, %

Zinc, %

7.9

1.8 0.6

213

76.0 11.40

1426.7 1.05 0.17

SAE 30 22.0

70.0

7.9 0.1

24396.9 11.41

1058.0

1.03 0.17 Compositional and physical characteristics for the two Mohawk oils are shown in table 6. Both were treated with the same commercial, cost-competitive SE/CC detergent-inhibitor treatment. No virgin oil viscosity adjusting stocks were used in either Mohawk oil. Engine test results (tables 7 and 8) indicate full compliance with the ASTM test performance criteria for

API Services SE/CC and the passing limits of MIL-L-46152A.

Our field experience with PROP re-refined oils has totalled 1.5 million miles. For the most part, this has involved PROP oils from North Carolina feedstock treated with the 'Universal' additive treatment of Program A. These field trials have been of a comparative

nature, conducted in a more or less uncontrolled testing environment. One 600 000 mile experience involved 19 Company-owned late model automobiles and pick-up trucks in pool service operating out of Bartl esvi 1 1 e. Service spanning one to two years to individual vehicles was trouble-free. Examination of operating records, comparing test units to the parallel operation of more than 100 similar vehicles running with Phillips' first line quality motor

oil, showed no differences in engine performance.

72
Table 7. Engine test results prop oil - program C. Engine Test

Ratings:

Avg. Rust

Avg. Sludge

Avg. Piston Varnish

Avg. Engine Varnish Ring/Land Varnish

Oil Ring Clogging

Oil Screen Clogging

Ring Sticking

Lifter Sticking

Avg. Cam/Lifter Wear, in Max. Cam/Lifter Wear, in Cam/Lifter Scuffing Viscosity Incr. @ 40 h Viscosity Incr. @ 64 h Oil Consumption, qts. OVERALL RATING

SEQ IIP 8.6

SEQ 1 1 ID

9.7

9.4

None None 0.0023

0.0043

None

2245

9.5 8.1

8.4

None

None

None

None

Table 8. Engine test results prop oil - program C. Engine Test CAT 1-H2 CLR L-38

Fed. Test Method 346 3405

Ratings: Top Groove Carbon, % 10% Weighted Total Deposit 133.6 Bearing Weight Loss, mg 26.8

Piston Varnish 9.6 OVERALL RATING PASS PASS Another 925 000 miles of experience has been obtained in a tire test fleet. One phase of their experience involved 30 passenger cars and light trucks (all gasoline engine-powered)

with curb weights 50 percent above normal. Units in "as is" condition, with from 100 000 to more than 400 000 engine miles of prior service were used. 650 000 miles were accrued

with these cars on high speed service. No initial nor final engine inspections were involved. Notwithstanding the initial high mileage of these cars, their operation during the five

months' trial was satisfactory and typical of prior experience in the fleet. The diesel truck experience was limited to 275 000 miles total, divided among six heavily

loaded tractor-trailers. Individual odometer readings ranged from 650 000 to 1.1 million

miles at the outset. Most were well within the fourth 250 000 mile bearing changeout period. Operation with PROP oil was limited to only 35 000 to 70 000 miles per vehicle and realis- tically was not sufficiently extensive to justify a performance claim. Presently, the State of North Carolina has several thousand gallons of SE/CC motor oils blended with PROP plant produced base oil. This SE/CC product is now being used in a variety

of State-owned vehicles on an uncontrolled basis. This experience began at mid-summer. To date reports indicate good acceptance and wholly satisfactory performance.

In closing, I want to report briefly on the status of the first two PROP plants which

you have read about in the press. The 2 MM GPY plant destined for North Carolina was demonstrated to and accepted by the State in late 1978. Subsequent independent laboratory engine

73
testing confirmed the PROP oil's SE/CC and MIL-L-46152 quality. For several months, this plant was operated intermittently as a prototype unit at its temporary site in Bartlesville

while North Carolina sought to come to a decision as to its permanent siting in the Raleigh

area. The plant has been ready for shipment for several months. North Carolina's expectation

is that the plant will be started up at their Garner (Raleigh suburb) site very early in 1980. Product use will be limited to the public vehicles of state and local government as stipulated

by State law to avoid competition with private enterprise. Fabrication of a 5 MM GPY PROP plant for Mohawk Oil Company, Ltd., is now complete. As I speak, final arrangements are being

made for its shipment to Mohawk's North Vancouver, B.C. plant site. Start-up is scheduled

during the first quarter of 1980. Mohawk has generated extensive favorable publicity for their re-refining program during the past year. Their announced plans include marketing of PROP re-refined oils meeting SE/CC/MIL-L-46152A and other industry requirements to all segments of the Western Canada market.

74
National Bureau of Standards Special Publication 584. Proceedings of Joint Conference

on Measurements and Standards for Recycled Oil/Systems Performance and Durability held at NBS, Gaithersburg, MD, October 23-26, 1979. (Issued Nov. 1980)

HISTORICAL PERSPECTIVE OF LUBRICANT DEPOSIT EVALUATIONS

AT SOUTHWEST RESEARCH INSTITUTE

J. N. Bowden and S. J. Lestz Southwest Research Institute

P. 0. Drawer 28510

San Antonio, TX 78284

1. Introduction

The purpose of a lubricating oil in the crankcase of internal combustion engines, in gear trains, and in turbine engines is to separate metallic surfaces that move with respect

to each other, thus minimizing friction and wear. In addition, the lubricating oil performs

as a heat transfer medium, a dispersant for wear and sludge particles, and a neutralizer for acidic combustion and/or oxidation products. If the lubricant fails as a coolant, dispersant, and neutralizer, then insoluble oxidation products are formed which deposit on metallic

surfaces, plug screens and filters, thus preventing the lubricant from performing its major

function, that of separating sliding surfaces. Mineral oils refined from petroleum crude provided satisfactory liquid lubricants for machinery for many years, but most modern equipment demands more from a lubricant than mineral oils alone can provide. Various additives have been developed to improve the properties of mineral oils and to give them desirable new properties. Aircraft turbine engine

lubricants are subjected to large volumes of high temperature gases which flow through the engine and to comparatively high loading on gearing. Thus, good thermal and oxidative sta- bility combined with good load carrying properties are essential, and synthetic lubricants

have been found to meet these requirements more adequately than petroleum-based lubricants.

At Southwest Research Institute, many projects have been devoted to learning more about

the basic mechanism of lubrication, the function of additives in lubricants, and evaluation

of the qualities of piston and turbine engine oils by means of bench tests development and subsequent correlation with full-scale engine tests. This presentation describes briefly

many of these projects involving piston and turbine engine lubricants.

2. Dispersancy Mechanisms

The basic mechanisms pertaining to the performance of oil soluble dispersants were in- vestigated using microscopy techniques to observe sludge agglomeration at elevated temperatures and to measure the electrophoresis of the particles dispersed in the oils [l] 1

. Figure 1 is a photograph of the microscope equipped with a heating stage used in this program,

and figure 2 shows the parts of the electrophoresis cell. The heating stage is capable of heating the sample, under close control, to 660 °F, and contains a removable slide holder

fitted with a cover glass to shield the objective lens. These techniques proved to be effective tools for studying and evaluating oil soluble

dispersants. As the dispersant concentration increases, the stability of a sludge suspension, when heat is applied, improves; and the electrophoretic mobility decreases. This mobility is nil at the maximum effective concentration for a stable sludge suspension,

showing that an equilibrium between the electrically charged entities in the system has been

established.

To investigate the mechanisms of ashless motor oil dispersant additives, which are mostly copolymers containing functional groups, an electron microscope technique was em- ployed [2]. It was learned the polymeric dispersants function much like the metal-organic

additives (fig. 3).

1 Figures in brackets indicate the literature references at the end of this paper.

75

Figure 3. Effect of dispersant concentration on el ectrophoretic mobility. Either the electrophoretic or sludge agglomeration techniques can be used effectively in studying the behavior of engine sludge dispersion in lubricating oils [3] (fig. 4). A procedure was developed which permitted the prediction of sludge rating in the low temperature dispersancy (LTD) engine test [4]. This test utilizes the CLR single cylinder

laboratory engine [4]. Examination of used oils with the microscope showed that high temperature was a major

cause of dispersant depletion, thus permitting the sludge to agglomerate and deposit on en- gine parts when a given sludge particle size is reached. Conclusions from this work were that: 1) Dispersant depletion can be studied by observing sludge agglomeration in the oil by optical microscopy. 2) Oil contamination by sludge precursors is greater at lower engine operating temperatures. Raising the oil tem- perature results in larger size oil sludge agglomerates, the deposition of which is facili- tated by cooling the oil. 3) The sludge agglomerate size technique can be used to pre- dict engine sludging at any time during an LTD test without the necessity of engine dis- assembly. 4) The agglomeration temperature analytical technique for screening new dis- persant oils correlates well with fleet and laboratory engine deposits and can predict LTD engine test ratings.

77
2

CONCENTRATION, WT %

Figure 4. Effect of additive concentration on sludge mobility (basic barium sulfonate).

3. Blowby Diversion

When combustion products, commonly called "blowby", are prevented from reaching an en- gine's crankcase, sludge formation is inhibited and lubricant life extended. Blowby diversion does not reduce an engine's inherent combustion leakage but is accomplished after the blowby gases leak past the compression rings and before the gases escape into the crankcase

atmosphere. Blowby, after leaking past the compression sealing zone, can be diverted from

the crankcase by one, or a combination of the following (fig. 5): Basic Method No. 1 - Di- version of blowby through a passage in the piston material to the combustion chamber. Basic Method No. 2 - Diversion of blowby to outside the engine by an isolated crankcase passage. Basic Method No. 3 - Diversion of blowby through the cylinder to outside the engine. Basic Method No. 4 - Diversion of blowby past the compression rings back into the combustion

chamber.

78
Single cylinder engine studies have demonstrated that the principle of blowby diversion

is feasible and can prevent better than 90 percent of the blowby from entering the crankcase.

The studies further indicated a significant reduction in sludge formation rates (increase in engine cleanliness), with decreases in ring wear and air pollution.

Use of basic method Nos. 2 and 3 permitted isolation and collection of blowby outside

the engine for thorough analysis. It was learned that this material is composed not only of hydrocarbon but also a significant concentration of nitric, sulfuric, and hydrochloric

acids.

Figure 5. Four basic methods of blowby diversion.

4. Engine Sludge Analysis

At low temperature engine operating conditions, sludge is often formed which results in deposits on engine parts. A study conducted at SwRI on the mechanism of sludge formation in- dicated that it is initiated by liquid oxidation products, inorganic salts, and polymerized

organic products that pass the piston ring zone [6]. During this work condensable blowby

products were analyzed and consisted of unburned fuel, water from combustion, oil insoluble

liquid oxidation products, and solid materials. Analysis of low temperature sludge generated in a laboratory engine was found to contain from 16 to 32 percent solid materials

depending upon the efficiency of the dispersant additive in the oil, 60 to 80 percent oil, and small amounts of water and fuel. Inorganic salts account for half the solid content of the sludge.

7q
5. Engine Varnish Varnish is a type of deposit that occurs on piston rubbing surfaces and can form on other surfaces in an engine. Varnish formation in spark ignition engines was investigated

to determine the interrelationship between fuels, lubricants, additives, and engine operating conditions [7]. A series of engine tests were conducted with fuels of varying compositions,

and different lubricants. The varnish deposits formed were removed and analyzed by nuclear magnetic resonance and infrared spectroscopy. From the data generated in this work, it was concluded that: 1) The main varnish precursors are fuel aromatic compounds. 2) Finished

lubricants act as varnish inhibitors. 3) Compression ratio, jacket temperature, and engine

load are the most important engine variables which affect varnish formation. 4) Nitrogen

fixation (N0 2 formation) contributes to varnish formation but does not have an overriding

effect. 5) Engine varnish composition is mostly alkaline in character and consists of primarily hydroxy and carbonyl organic compounds, but sulfur and nitrogen hydrocarbon derivatives are also present. In addition, lead salts are part of varnish but are not a prerequisite to varnish formation.

6. Thermal Oxidation Stability of Gear Lubricants

A method for measuring the thermal oxidation stability of gear lubricants was developed

at the Army Fuels and Lubricants Research Laboratory, SwRI, which became a part of Federal Test Method Standard No. 791-B, and was assigned Method No. 2504. The method evaluates the deterioration of gear lubricants under severe oxidation conditions and consists of placing a sample of the lubricant in a gear case in which two spur gears and a test bearing are opera- ted under load while heat is applied and air is bubbled through the lubricant (fig. 6). The temperature of the sample is maintained at 325 °F and the test is continued for 50 hours. Every ten hours a sample is taken for viscosity measurement, and if 100 percent increase in viscosity is observed, the test is stopped. The lubricant sample is drained out of the gear

case and tested for viscosity, acid number, pentane and benzene insolubles. Deposit on gears, various parts of the gear case and catalyst are rated for color, hardness, thickness,

and type, such as lacquer or sludge. Several engine oils were evaluated by this procedure

to study the high temperature oxidative effects; however, the repeatability of the test data

was not good. The apparatus was modified to evaluate the oxidation corrosion tendencies of crankcase

lubricants [8]. The modification consisted of removing the test gears, copper catalyst, gear-loading mechanism, and air supply system. The lubricant compartment was modified to accommodate a driveshaft seal, and a test bearing connecting rod journal of special design

was mounted on the driveshaft (fig. 7). Lubricants evaluated in this apparatus for copperlead bearing weight loss compared with results for the same lubricants evaluated in L-38 single cylinder engine tests (fig. 8).

7. Turbine Lubricants

As stated earlier, the requirements of aircraft turbine engine lubricants are considerably more stringent than those of automotive engine lubricants. Several procedures have been developed and investigated at SwRI to evaluate oxidation, corrosion, thermal stabilty,

and depositing characteristics of synthetic turbine engine lubricants.

8. Oxidation-Corrosion-Deposition and Thermal Stability Characteristics of Aircraft Lubricants

A glassware test to investigate the oxidative, corrosive, depositing and thermal sta- bility characteristics of synthetic aircraft turbine lubricants was used extensively at SwRI

[10]. The procedure became a Federal Standard Method and is a required test for Military

Specification, MIL-L-7808 type lubricants [11]. During the course of this work a light meter for evaluating deposits was developed which had good precision and excellent cor- relation with visual ratings. The effect of metal and moisture on the stability of the lubricant was found to vary considerably depending on the test lubricant (fig. 9). Thermal stability investigation carried out in an inert (N 2 ) atmosphere indicated that various metals, notably magnesium, significantly reduced lubricant temperature tolerance.

80

Figure 7. TOST apparatus modified for evaluation of oxidation and corrosion tendencies of crankcase lubricants.

9. Micro Panel Coker

Over the years, considerable attention has been devoted to the refinement and develop- ment of various bench-scale test devices intended to screen aircraft turbine engine lubri- cants on the basis of deposition tendencies. The thermal stress of the lubricant under such conditions results in oxidative breakdown of the fluid and the formation of deposits which

impede satisfactory operation of the power plant.

A liquid-phase micro panel coker was designed and developed primarily for use in screening synthetic lubricants, on the basis of deposit formation, in instances where only researchsize sample quantities are available [12] (fig. 10). The device, which requires less than

75 ml of sample per test, is capable of operation to 1000 °F panel temperature and exhibited

good correlation wth a full-scale, RTD "TR" panel coker which requires a sample volume of approximately 650 ml per test (fig. 11).

82
1500

EJ000

JJ 500

i '

1

1 1 1

1

1

1 1 1 n 1

1 1 1 1 1

1

1

o L-38 ENGINE

a BENCH TEST

2 ,ooT

bJ 75 - z 50

5 25

FAIL PASS

ESM. n Mini il null 0 10 20 30 40 50

LUBRICANTS

Figure 8. L-38 engine and bench test bearing weight loss.

A vapor-phase micro panel coker was also developed and was employed in a less extensive

study of vapor-phase deposition, as opposed to the essentially liquid-phase condition found

in the normal panel coker design. Both micro panel coker models were utilized in an experimental investigation of the effect of moist air on test lubricant performance (fig. 12). A varying response to moisture

was found. The performance of some fluids was unaffected, while others showed improvement,

and some indicated a deleterious effect. In addition, lubricant sensitivity to moisture was dependent upon the coker type and was, in some cases, reversed between the two coker models

when compared with the normal procedure using dry air.

10. Hot Wall Deposition Rig

An expanded program to study the deposition and degradation characteristics of aircraft

turbine lubricants involved the fabrication and operation of a test rig designed to simulate

the conditions of actual engine operation with regard to temperature, lubricant dispersion,

and flow rate that occur in the vicinity of the No. 2 rear bearing support of a J-57 jet

engine. In this test, the No. 2 rear bearing support, herein called the hot-wall, is used

as the test specimen on which deposits are caused to form by subjecting the front surface of the specimen to a lubricant fog while heat is applied to the back surface (fig. 13) [13]. A schematic diagram of the hot-wall deposition rig is shown in figure 14. The test oil sump L and makeup oil reservoir U are charged with 2000 and 1000 ml of test lubricant, respectively.

The lubricant is heated to 350 °F and pumped to the test specimen A, where it is fogged through

nozzle E on to the hot-wall, which is kept at the desired temperature between 500 and 560 °F. Data from this test identified heating fluid temperature, atmosphere type, and test time as significant main effects of the deposition process.

A continuing investigation led to the discovery of the presence of appreciable metal (iron) content in the deposits recovered from the conventional bearing deposition tests and full-scale engine tests. The concentration of iron in the test lubricant in the principal deposits was monitored by atomic absorption spectroscopy. A direct indication of the extent

of wear metal generation was provided by weight loss measurements of spring-loaded mild steel wear plates mounted within the test-lubricant sump (fig. 15). Significant deposit rating

increases were found in many instances, dependent upon the test lubricant and magnitude of wear [14] (table 1). 83
Figure 9. Typical sample tube deposits.

84

Figure 11. Correlation of deposit weight between RTD panel coker and liquid-phase micro panel coker.

11. Rotating Cylinder Rig Experiments were conducted with a device known as the rotating cylinder rig for the formation of controlled-thickness thin films (0.004 in) at temperatures in the range of 350°

to 550 °F (fig. 16). Analytical techniques for detection of lubricant or additive con- sumption and degradation products included liquid chromatography and gas chromatography/

mass spectroscopy. Studies were conducted with selected polyol ester and diester base stocks, both with and without additives. Experiments showed that the antioxidants effectively

retarded oxidation and deposition for both ester base stocks up to the time of complete additive consumption. A beneficial synergistic effect on deposition was noted at one concentration using the antioxidants in combination. The findings strongly suggest that

an interaction between the ester oxidation products and system wear metals is a significant factor in the deposition mechanism for both ester types [15].

12. Engine Simulator Test for Lubricant Evaluation

The Air Force Aero Propulsion Laboratory engine simulator was designed to provide a flexible test facility with the capability of closely simulating the critical temperatures

and oil flow variables experienced by the lubricant in the full-scale aircraft turbine en- gine. The No. 4-5 bearing compartment areas of a J-57 turbine engine are used as the basic section of the simulator (fig. 17). The simulator is driven by a 100-hp variable-speed

drive system through the accessory drive gearbox, providing simulator mainshaft speeds up to 10 000 rpm. Electrical resistance heaters are used to heat the air surrounding the oil- wetted areas within the No. 4-5 bearing compartment areas to the controlled test temperatures. Results obtained on eight lubricants, for which full-scale engine data are available, show a 90.4 percent correlation coefficient of the deposit ratings obtained using the AFAPL engine simulator and the deposit ratings obtained from the No. 4-5 bearing compartment areas from the engine tests [16] (figs. 18 and 19).

86
87
88
39
O Test No 824 % Test No. 826 o o o o o 6

Figure 15. Typical wear metal trends in hot-wall deposition tests with wear

specimens.

TO GC

ELECTROSTATIC

PRECIPITATOR

SCAVENGE

PRESSURE

RELIEF LINE

X—«*- GAS {AIR OR N 2

)IN > CONDENSATE

SEAL R0T0R\ ^CYLINDER

RETURN LINE

| ill' '\

T SJ" COOLER L_l

FILTER H TL-^ggr^ifUMP

~? tz^£r>— i I 3 LUBRICANT-IN PUMP

3-WAY

VALVE

LUBRICANT RESERVOIR

Figure 16. Rotating cylinder rig lubricant/atmosphere flow systems.

90
Table 1. Summary of hot-wall deposition test results on the effect of wear metal (Fe). Mean Results Specimen Lubricant weight Deposit 100 °F vis NN change,

code loss, mg rati ng change, % mg KOH/g 0-64-2 NP

a 36(4)

b

g 46 43(4) 0 34 0-64-13 NP 35(3)

62(3) 7^3 0 07 0-64-25 NP 14(5)

806 91(3) 10.2 1 00 0-65-16 NP 29(5) 381 47(4) iiJ 0 54 0-67-20 NP 54(7) 9 3 0 34 81(2) 8^5 0 30 0-67-21 NP 31(3) 88(3) 20.4 0 95 0-68-1 NP 41(3)

437 79(3) 15! 3 0 74 0-68-7 NP 26(2)

68(2) 7'.b 1 68 0-68-9 NP 37(3)

355 62(4) 1.6 0 34 0-68-13 NP 22(2) 2.8 0 26 37(2) 0-69-2 NP 31(7) 12.1 0 67 124 58(4) 12.1 0 56 0-70-2 92(2) 49.1 29 8 347 116(2) 62.7 36 1 a NP-wear specimens not present in system.

13 Numbers in parentheses denote the number of tests run to obtain the indicated means.

91
9Z
1 1 TOTAL FULL-SCALE ENGINE DEPOSIT RATING i ENGINE 4-5 AREA DEPOSIT RATING x 4 .31

\ \ ENGINE SIMULATOR DEPOSIT RATING x 4.31

Figure 18. Comparison of estimated and actual total engine deposit ratings.
o

18 -

r 6

! .1

EAR REGRESSION

LINE Y = 7.23 + .64X CORRELATION COEFFICIENT

r = 90.4 PERCENT

20 22 24 26

4-5 AREA FULL-SCALE ENGINE DEPOSIT RATING

Figure 19. AFAPL engine simulator deposit ratings versus deposit ratings of the 4-5 area from full-scale engine tests. Concluding Remarks

The foregoing discussion presented numerous bench tests investigated at SwRI which were

intended to evaluate the performance of automotive engine and gear oils, and aircraft tur- bine lubricants. In most cases the tests were designed to simulate certain aspects of the environment seen by the lubricant while performing its function, and lubricant degradation

with subsequent deposit formation are the parameters measured. Although in many instances

good correlation with specific engine tests were achieved, the final measure of acceptability

of a finished lubricant for military applications remains the full engine tests for engine

oils; automotive gear tests for gear oils, and full-scale turbine engine tests for the air- craft lubricants. The tests discussed here are excellent screening devices for new experimental lubricant formulations. References

[1] Bowden, J. N. and Dimitroff, E. , Electrophoresis of dispersant lubricating oils, paper presented at the Division of Petroleum Chemistry of the American Chemical Society, 140th National Meeting, 6, [4], B5, Chicago, Illinois (September 3-8, 1961).

[2] Bowden, J. N. and Dimitroff, E. , Mechanism studies of polymeric dispersants, paper presented at American Chemical Society Symposium on Polymers in Lubricating Oils,

Z» B-45, Petroleum Division, Atlantic City, New Jersey (September 1962).
[3] Dimitroff, E. and Bowden, J. N. , A theory on the mechanism of dispersancy in oil medium, paper presented at American Chemical Society Symposium on Dispersancy in Oil Medium, Division of Colloid and Surface Chemistry, Atlantic City, New Jersey (Sep- tember, 1962).

[4] Dimitroff, E. , Moffitt, J. V., and Quillian, Jr., R. D. , Dispersancy prediction by optical microscopy, paper presented at the Society of Automotive Engineers, National Fuels and Lubricants Meeting, Philadelphia, Pennsylvania, paper no. 600B (November,

1962).

[5] Quillian, Jr., R. D. , Meckel, N. T. , and Moffitt, J. V.-, Cleaner crankcases with blowby diversion, paper presented at the Society of Automotive Engineers' Automotive

Engineering Congress, Detroit, Michigan, paper no. 801B (January, 1964).

[6] Dimitroff, E. and Quillian, R. D. , Jr., Low Temperature Engine Sludge, What? Where?

How?, paper presented at the Society of Automotive Engineers, International Automotive

Engineering Congress, Detroit, Michigan, paper no. 951A (January, 1965).

[7] Dimitroff, E. , Moffitt, J. V., and Quillian, Jr., R. D. , Why, what, and how: Engine

varnish, Journal of Lubrication Technology, 406-416 (July, 1969).

[8] Thermal Oxidation Stability of Gear Lubricants, Federal Test Method Standard No. 791, Method 2504 (January 15, 1969).

[9] Staudt, J. J., Lepisto, P. R. , and Vitkovits, J. A. , A bench technique for evaluating

high temperature oxidation and corrosion tendencies of automotive crankcase lubricants, paper presented at Society of Automotive Engineers, West Coast Meeting, San Francisco, California, paper no. 680538 (August, 1968).

[10] Cuellar, J. P. and Baber, B. B. , Studies on the Oxidation-Corrosion-Deposition and Thermal Stability Characteristics of MIL-L-7808-Type Lubricants, Technical report AFAPL-TR-72-45, Southwest Research Institute (June, 1972).

[11] Corrosiveness and oxidation stability of aircraft turbine engine lubricants, Federal Test Method Standard No. 791B Method 5307 (June 30, 1974).

[12] Cuellar, Jr., J. P., and Ku, P. M. , Development of a Micro Lubricant Deposit Test, Technical report AFML-TR-67-438, Southwest Research Report (January, 1968).

[13] Cuellar, Jr., J. P., Montalvo, D. A., and Baber, B. B. , Studies with Synthetic Lubri- cants in the Hot-Wall Deposition Rig, Technical Report AFAPL-TR-72-25, Southwest

Research Institute (June, 1972).

[14] Cuellar, J. P. and Baber, B. B. , Hot-Wall Deposition Test Results on the Effect of Wear Metal, Technical Report AFAPL-TR-73-123, Southwest Research Institute (November,

1973).

[15] Cuellar, Jr., J. P., Mechanism of Turbine Engine Lubricant Deposition, Technical Re- port AFAPL-TR-79-2037, Southwest Research Institute (May 1979).

[16] Baber, B. B. , Tyler, J. C. , and Valtierra, M. L. , Development of the AFAPL Engine Simulator Test for Lubricant Evaluation, Technical Report AFAPL-TR-75-38, Southwest

Research Institute (June, 1975).

95

National Bureau of Standards Special Publication 584. Proceedings of Joint Conference

on Measurements and Standards for Recycled Oil /Systems Performance and Durability held at NBS, Gaithersburg, MD, October 23-26, 1979. (Issued Nov. 1980)

CURRENT ACTIVITIES OF THE NATIONAL BUREAU OF STANDARDS

RECYCLED OIL PROGRAM Donald A. Becker

Recycled Oil Program Office of Recycled Materials

National Bureau of Standards Washington, DC 20234

For those of you who are not familiar with the origin or responsibilities of the National Bureau of Standards (NBS) Recycled Oil Program, the program history will be reviewed very

briefly. In December of 1975, the Congress of the United States passed the Energy Policy and Conservation Act (P.L. 94-163, Section 383; 42 U.S.C. 6201 et seq. ) This legislation stated that the National Bureau of Standards was to develop test procedures which could be used to establish the substantial equivalency of recycled oil products when compared to virgin oil products.

In response to this legislation, in 1976, NBS formed the Recycled Oil Program in order to develop the technical expertise necessary to address this problem. Shortly after formation, Jack Comeford joined the program, and the technical effort at that time consisted of the two

of us with several part-time laboratory technicians, plus the technical expertise in specific

areas around the Bureau, such as analytical chemistry, calorimetry, etc. In June of 1977, Bob Pedall of Motor Oils Refining joined NBS as an Industrial Research Associate, sponsored

by the Association of Petroleum Re-Refiners (APR). Bob was very effective in helping us learn more about the petroleum test procedures that are used with re-refined oils and recycled oils in general. Soon after our formal organization, the goals and objectives of the Program were

established. Since these help to provide insight into our efforts and responsibilities, they

are included here. Our goal is "to provide the measurement methods and standards required for effective utilization of recycled petroleum products." This goal was to be carried out by achieving the following three objectives.

1) Establish the scientific and technical basis for characterization of recycled petroleum oils.

2) Develop and evaluate test procedures for establishing the substantial equivalency

between recycled and virgin petroleum oils.

3) Provide technical information and data to encourage the effective utilization of recycled petroleum oils. Note that in the second objective as shown here, the requirement for NBS as described in the legislation is not to prove equivalency, but to develop test procedures which can be used

by any knowledgeable person to establish or confirm such equivalency. Many of the research

efforts by other organizations which have been looking at recycled oil have established

without question that a particular batch of re- refined oil is equivalent to a high quality

virgin oil. The problem was, and still is, can a set of tests be developed to establish on a regular and reasonable basis that a particular re-refined oil is in fact a high quality

lubricating oil

.

In the development of an NBS Program, four groups of end-use products, or phases, have been identified. These phases were based on both perceived need as well as technical ability

to respond. The first phase is on test procedures required to establish the equivalency of a recycled oil when used as a burner fuel. This phase has now been completed and the results

97
are briefly discussed below. The second phase is on test procedures for recycled oil used as engine oils, and we are in the process of working on the first portion of this phase, engine crankcase oils. The third phase of our program is on recycled oils used as hydraulic oils, and the fourth phase is on industrial oils (e.g., cutting oils, grinding oils, rolling oils). We will address the third phase of our effort after we have completed the second phase on engine oils, and so on. The report on Phase 1, Test Procedures for Recycled Oil Used as Burner Fuel, was completed

for the operational test procedures in September of 1978 and transmitted to the Federal Trade Commission (FTC). Several additional test procedures for potential environmental concerns were completed in August of 1979, and were transmitted to the FTC in September of 1979. In the first portion of this report, on the operational test procedures required for equivalency,

8 test procedures were recommended for modification or addition to the test procedures contained in the ASTM Specification (D396) and the Federal burner fuel oil specification

(Federal Specification W-F-815c). In the environmental section of this report, three additional test procedures have been evaluated and included, should the Environmental Protection Agency

feel they are necessary. These tests procedures include analysis for polynuclear aromatics, chlorine and bromine, and lead. This entire report is available from NBS upon request.

In the fall of 1978, NBS received a Congressional appropriation which enabled this program to expand and establish the technical effort which we felt was necessary for initiating work on the difficult question of substantial equivalency for engine oils. We have now developed a rather extensive technical program, and I will describe various aspects of this program at this time. Within the matrix management system as found in the National Measurement Laboratory of

NBS, the Recycled Oil Program acts as an information source, a coordination system and a funding organization. We provide a focal point for persons both within and outside NBS, to request and obtain information on the subject of oil recycling and measurement methods and standards connected with oil recycling. In addition, the Recylced Oil Program provides coordination and contact with many outside organizations, including the American Society for Testing and Materials (ASTM), the Society for Automotive Engineers (SAE), the American Society

for Lubrication Engineers (ASLE), the Association of Petroleum Re-Refiners, and the American Petroleum Institute (API). The actual research and development work in the area of recycled

oil is located within the various technical divisions in NBS, as well as in several projects located outside NBS. There are 8 major R&D projects funded by the Recycled Oil Program, and these will be discussed individually below. The first research project is in the Tribochemistry Group, which was formerly the recycled oil laboratory. This group has now been expanded and transferred to the Chemical Stability and Corrosion Division within the Center for Materials Science. This effort is actually a number of activities, and contains a major portion of the NBS R&D effort directed

towards recycled oil. Specific aspects of this work will be discussed in more detail later in this paper. The second project is in the area of lubricated wear, and represents the activity taking place within the Wear Group in the Metallurgy Division, also in the Center for Materials

Science. They are investigating certain aspects of lubricated wear, particularly with respect

to the effect of various metallurgies and of surface topography on bench wear test procedures. Some of the activities of this group will be presented by Louis Ives later in this meeting. Third, we have a significant effort in the Inorganic Analytical Research Division involving the development and modification of test procedures for the analysis of trace

elements. In particular, the evaluation of lead analysis procedures for the environmental portion of the fuel oil tests required a great deal of effort by this Division. They are also working on the development of specific analytical methodology to support work of the Tribo- chemistry Group as well as the development and certification of Standard Reference Materials

(SRMs) of used oil and of wear metals in oil. The Organic Analytical Research Division was instrumental in the evaluation of a method

for analysis of polynuclear aromatics in fuel oils, and at the present time is looking at 98
the determination of polychlorinated bi phenyls in oils. You will hear a talk on this work by Steve Chesler later in this meeting. The fifth project is the antioxidant capacity test which was developed by the Ford Motor

Company, and that we have also set up for evaluation here at the National Bureau of Standards. Dick Rebbert will discuss his work later in the meeting, and we have great hopes for this

test. The sixth project is differential scanning calorimetry (DSC), and this test method will

be described more fully by Jim Walker, later in the program. The last two projects are research projects that we have initiated outside of NBS. The first is the microoxidation test that Elmer Klaus is modifying for use with petroleum oils, and he will report to you on it Thursday afternoon. The second one is a cooperative engine deposit study, an interagency agreement with the Army that we just initiated, and you heard

about the historical aspects of the work that Southwest Research Institute did for the Army

just a few minutes ago. This organization has had extensive experience in the evaluation of engine deposits and we look forward to a very fruitful and useful cooperative effort with

them. The NBS Recycled Oil R&D has been expanded considerably since the early stages of the program, and the Tribochemistry Group now has eight full time scientists working on these projects as well as five part time people working in the laboratory, plus a secretary. As many

of you involved in scientific research can well appreciate, it has taken a considerable period

of time to locate and bring in people with appropriate experience and background. These

scientists are providing a high quality research effort in the area of petroleum testing, obtaining and modifying appropriate laboratory facilities for this work, and gaining experience with the rather extensive equipment and test procedures that are involved in petroleum oil evaluation.

The Tribochemistry Group has activities in the 4 general areas of physical properties,

chemical properties, hydrocarbon type characterization, and performance test development. There is also an oil storage and blending facility to carry out the logistical requirements of

the program. In the storage blending facilities, the modifications are now essentially

complete and we have a storage capacity of about 150 drums plus an additional 500 gallons in one and five gallon cans. We have a blending capacity of 60 gallons, and at the present time, have 19 re-refined base stocks in our inventory. Of these, eight of them are in ten drum

quantities, and these are the base stocks which we have obtained directly from a number of re-refiners and are in the process of characterizing in order to make them available to organizations requesting samples of re-refined oils for their testing. Two of these oils have already been obtained by the Army for use in their investigation of the MIL-L-2104C

specification using single cylinder diesel tests. As part of this project, we are requesting

that each organization which obtains samples of these oils for testing and evaluation provide

the results and data to the NBS Recycled Oil Program, and this information will be compiled

and published in the open literature. In addition to those initial eight re-refined oils, we

have nine other re-refined oils in one drum quantities, as well as two additional re-refined

oils in five - 15 gallon quantities each. Besides the re-refined oil base stocks, we have 39 different virgin oil base stocks which

we will be testing. Since the legislation requires us to investigate the "substantial equivalency" of a re-refined oil when compared to a virgin oil, we feel it is necessary to fully understand the important characteristics of virgin oils as well. Next, we currently

have 56 different additive components, which have been obtained from additive companies. We

will be using these additive components in our program to investigate the additive response of re-refined oils using various bench tests. Also, as part of this effort, we have 21 of the ASTM reference engine oils. The physical properties under investigation include as a first priority: viscosity at

40 and 100 °C, density, (API gravity), color, pour point, boiling point distribution using gas chromography , and flash point. In addition, the derived property, viscosity index, is of interest and will be evaluated. Some additional physical property tests that we will also be looking at, after the first priority tests have been investigated, include refractive index, average molecular weight, molecular weight distribution, and cloud point. Further, the derived physical properties of carbon distribution using the NDM method, the viscosity-gravity

constant, and the refractivity intercept may be of interest.

99
Chemical properties of first priority include the test procedures for carbon residue,

total acid number, sulfated ash, saponification number, sulfur, nitrogen, chlorine, and infrared spectroscopy scan. With the exception of the infrared scan, these are test proce- dures that are included in the revised military specification MIL-L-46152A. There are a number of additional chemical properties which also may be of interest for the characterization of lubricating oils, and these are: water content, oxygen, bromine number, aniline

point, coagulated insolubles (including both pentane insolubles and toluene insolubles), precipitation number, metal content (by atomic absorption spectroscopy or emission spectroscopy), ultraviolet spectroscopy, demulsibil ity characteristics, and a copper corrosion test to determine active sulfur.

In the hydrocarbon type characterization effort within the Tribochemistry Group, they are looking at several different methods of column chromatography to determine the various hydrocarbon components using clay and silica gel/alumina columns. At the present time, various combinations of these columns can determine the quantities of saturated hydrocarbons, aromatic hydrocarbons (including monoaromatics , diaromatics, and polynuclear aromatics), and polar hydrocarbons. The NDM carbon distribution method can be applied to lubricating oils directly, as well as to the various fractions obtained by the column chromatography procedures mentioned above. There is an effort to prepare various fractions of lubricating oils by gradient elution through an alumina column. These fractions can then be used to establish the effect of various polar fractions on some of the bench tests procedures that are being developed through the performance test R&D. UV and IR methods will also be examined for possible use in the characterization of hydrocarbon types. Efforts in the area of hydrocarbon type characterization which are outside the Tribo- chemistry Group include the application of nuclear magnetic resonance by a state-of-the-art

fourier transform NMR spectrometer which is currently being set up as part of another program,

and the application of high resolution mass spectrometry in cooperative efforts with several major oil companies. In addition, the Bartlesville Energy Technology Center will be running

high performance liquid chromotographic separations coupled with low resolution mass spectro- metry on a number of oil samples as part of the ASTM/NBS base stock consistency study that Ken Frassa will be talking about tomorrow morning, and the results from this study should be very

useful in the evaluation of which of these hydrocarbon type characterization methods actually provides accurate results in terms of saturates, aromatics, naphthenics, polar compounds, etc. The Tribochemistry Group is interested in development of performance tests for in the four general areas shown here: lubricated wear, oxidation stability, deposit formation, and rust and corrosion. However, these efforts have been largely limited at the present time until the first two areas of physical and chemical properties are completed. Instead, much of this effort is being accomplished by various research efforts outside the Tribochemistry Group, which have already been described. One of the most important aspects of the performance test projects are evaluation of the "additive response" of lubricating oil base stocks. Since it has been stated that re-refined

oil may very well have an "additive response" which varies from batch to batch, we feel it is necessary to develop test procedures which are capable of evaluating the additive response of

a re-refined (or virgin) base stock. One way to do this is to use a standard additive

package, perhaps at considerably smaller treat levels then would normally be used in service,

and determine the effect of different batches of a particular re-refined oil on the perfor- mance of that base stock/package combination. As you can imagine, trying to establish rather

or not there i_s a significant additive response component for re-refined oils may very well be much more difficult than monitoring such a response once it is found. I feel it is important

that we establish whether or not this is a real concern, and whether or not performance tests must be developed which are capable of monitoring this characteristic in re-refined oils on a regular basis.

I now will briefly mention the various performance tests that we are involved with at the present time. In the area of lubricated wear, Lou Ives from the Metallurgy Division will be talking about their work on the ring and block tests and their evaluation of the pin and V test using Falex equipment for both of these tests. The Tribochemistry Group is also involved

in lubricated wear, and will be discussing their work on the 4-ball wear test. The cam and lifter test for determination of lubricated wear is one that is of great concern at the

100
present time in the industry, and this type of wear is currently being monitored in several of the engine sequence tests. We are in the process of obtaining a MIRA cam and lifter bench

rig, which can be used to look at this type of wear.

In the area of oxidation stability, papers on work supported by NBS will be given during

this Conference on the Ford anti-oxidant capacity test, a differential scanning calorimetry

test, and the microoxidation test by Elmer Klaus of Pennsylvania State University. In addition, the chemi luminescence test is currently of interest, and we hope to provide some input to this test which appears to be a very useful method for looking at oxidation

stabi 1 ity. Future research and development by the Tribochemistry Group will include the evaluation

of oil thickening tests, the rotary bomb oxidation test, and the steam turbine test--commonly

known as ASTM D943--and comparison of these tests to other oxidation stability tests as far

as reliability, precision and accuracy, and usefulness of the information obtained.

In deposit formation, much of the NBS effort will be through a cooperative research project with the U.S. Army Fuel and Lubricants Research Laboratory in San Antonio. Also, eventually we will be looking at the panel -coker test for deposits and may very well evaluate

various dispersancy tests, an important characteristic of formulated lubricating oils. Further, there are currently two engine sequence tests which are concerned with the area of rusting and corrosion. These are the L-38 Bearing corrosion test, and the II D rust test. The possibility of evaluating re-refined oils for additive response to these tests will certainly be considered. Recent progress of the NBS Recycled Oil Program include the following:

1) Transmittal of the test procedures of Phase I of our program on test procedures for recycled oil used as burner fuel to the Federal Trade Commission. (Copies of this report are available upon request.)

2) Initiation of work on Phase II of the NBS program, test procedures for engine crankcase oil, was initiated in November of 1978.

3) Proceedings of the last NBS Conference on Measurements and Standards for Recycled

Oil were recently issued as NBS Special Publication 556. 4) Consumation of an interagency agreement with the U.S. Army MERADCOM on a cooperative

program for investigation of mechanisms and development of test procedures for sludge and deposit formation. This is a two year agreement and we are looking forward to continued

interaction with the Army in this area, and expect that their long standing expertise in the area of sludge and deposits will provide a substantial effort on the problems of testing for sludge and deposit tendencies of lubricating oils.

5) Initiation of ASTM-NBS base stock consistancy study in March of 1980. Ken Frassa

will talk about this program in detail tomorrow morning and we look forward to this cooperative effort by many different organizations. I feel information on base stock consistency is crucial in the determination of which test procedures might be necessary to adequately characterize re-refined (and virgin) oils. Finally, I want to describe the various mechanisms NBS uses to provide information on our work to you, the consumer. The Energy Policy and Conservation Act requires that the NBS Recycled Oil Program provide reports on our test procedures to the Federal Trade Commission.

We have taken the philosophy that everything we provide to the FTC is available to anyone who

should request it. Should you be interested in receiving one or more of our reports or publications, please let me know and I will be happy to see that you will receive them. We

also feel that it is important that information on what we are doing be made available to ASTM, SAE, ASLE, to the API and the APR, and I make it a point to attend at least one of these

meetings each year to report on what we are doing and why.

I believe this information transfer is crucial to assuring people that our legislative

requirements are being actively complied with, and on a technically defendable basis.

101
Additional delivery mechanisms include conferences and workshops, publications, development of Standard Reference Materials, and providing technical advise and assistance where needed. In particular, we feel it is important to provide NBS technical assistance to other government

agencies (including Federal, State and local agencies), and both the Energy Policy and Conservation Act and the Resource Conservation and Recovery Act contain specific references to support for the education of both public and private sectors on the merits of increased use of recycled oil.

In conclusion, I wish to invite all of you to provide input into the NBS Recycled Oil Program, and to write me on what you feel the needs and the problems are in the area of oil recycling and on how NBS can help solve these problems, particularly in the area of new or

improved measurement methods and standards. I always stand ready to discuss this with any of

you, and feel free to discuss this with me at this meeting, by mail, or by telephone.

102
Session 3 LUBE OIL BASE STOCK CHARACTERIZATION

103

National Bureau of Standards Special Publication 584. Proceedings of Joint Conference

on Measurements and Standards for Recycled Oil /Systems Performance and Durability held at NBS, Gaithersburg, MD, October 23-26, 1979. (Issued Nov. 1980)

ASTM/NBS BASE STOCK CONSISTENCY STUDY

K. A. Frassa

Mobil Oil Corporation

150 East 42nd Street

New York, NY 10017

This paper summarizes the scope of a cooperative ASTM/NBS program established in June

1979. The contemplated study will ascertain the batch-to-batch consistency of re-refined and virgin base stocks manufactured by various processes. This activity, which is presently being

implemented, falls under ASTM Committee D-2, Technical Division P - Recycled Petroleum

Products, Section II - Used Oil and Base Stocks. A total of 12 different organizations have volunteered to participate in this study: Barttesville Energy Technology Center Motor Oils Refining Co. Chevron USA National Bureau of Standards

Lubrizol Corporation National Research Council of Canada Meradcom Savant, Inc. Mobil Oil Corporation Suntech, Inc. Texaco Gulf Research and Development

For one year, approximately eight to ten different base stocks samples, table 1, will be obtained by NBS every two weeks. One set of bi-monthly samples will be forwarded to each participant, on a coded basis monthly. As noted, seven to eight samples will be obtained from

six different re-refining processes and two virgin oil samples from a similar manufacturing

process. Table 1. Base stock samples.

No. of Samples Process Re-refined stocks 1 Acid/clay

1 Short path vacuum dist (tentative)

2 Vac. dist/acid/clay

1 Clay

1 Demetal ize/f ilter/hydrogen (tentative)

Virgin stocks 2-4 Vac. Dist/solvent ext/hydrogen

The participants will report their results on a monthly basis. The second set of samples

will be retained by NBS for an interim monthly sample study, if required, based on data

analysis. Each sample's properties will be evaluated using various physical tests, table 2, chemical tests, table 3, and bench tests, table 4. The total testing program should define

the batch-to-batch base stock consistency short of engine testing.

105
The first monthly samples are tentatively scheduled for shipment to participants during January 1980 and monthly thereafter for 12 consecutive months. Over 500 individual tests will

be run on base stocks from each manufacturer. The total testing program will exceed 5 000

tests. The results will be analyzed on a statistical basis in a report targeted for mid- 1981. Table 2. Physical property tests. Test

Gravity, °API Color; foam Viscosity @ 40 & 100 °C Viscosity Index

Pour point, °C Carbon residue Boiling point dist

Cold cranking simulator 0° to -40 °C Mini-rotary vise. 10 °C to -40 °C Brookfield viscosity 0, -20, -40 °C Refractive index

Demul sibi 1 ity

Fi Iterabil ity h

Participant

Suntech

NBS

Table 3. Test

Tan Saponification

Nitrogen, chlorine, sulfur

Low resolution mass spec (selected samples)

Liquid chromatography

Emission spectrograph

Halogens

Nitrogen, oxygen

Diff. scanning colorimeter

Differential infra-red Sunlight stability Additive compatibility

Glycol

Chemical property tests. Participant Meradcom

BETC Texaco Motor Oils Ref

NBS

Mobil

Nat. Res. Canada

Lubrizol Gulf

106
Table 4. Bench tests. Test

Engine oil additive package oxidation response

Engine oil additive package

EP response

Rusting

LUBTOT

Seq III C simulator

Ford anti-oxidant response

RBOT (base stock + additive) Turbine oil oxidation

(selected samples) y

Participant

Chevron

Lubrizol Meradcom

Suntech

NBS

Nat. Res. Canada

107

National Bureau of Standards Special Publication 584. Proceedings of Joint Conference

on Measurements and Standards for Recycled Oil /Systems Performance and Durability held at

NBS , Gaithersburg, MD, October 23-26, 1979. (Issued Nov. 1980)

PROPERTIES OF CANADIAN RE-REFINED BASE OILS

P. L. Strigner

National Research Council of Canada Division of Mechanical Engineering

Ottawa, CANADA K1A 0R6

1. Introduction

Owing to limited laboratory facilities, Canadian oil re-refiners employing the acid/clay

process have sought aid from the Fuels and Lubricants Laboratory of the National Research

Council of Canada (NRC) in the laboratory evaluation of their products, including base

stocks, finished oils and waste oil feedstocks. The NRC laboratory has provided this evaluation service since 1967 even though its own facilities have not been extensive. In addition,

base stocks from a number of experimental processes submitted by the re-refiners and others were evaluated. Even industrial and hydraulic reclaimed oils have been evaluated.

This presentation on properties of re-refined oils covers only the evaluation of base

stocks obtained principally from used service station oil drainings by the acid/clay process

(table 1). Data were condensed from a more comprehensive NRC, Division of Mechanical Engi- neering report MP-75 [l] 1

. Since numbers by themselves often have little meaning, reference

data were obtained on a small number of refined or virgin base stocks as well (table 2). Furthermore, the summarized Canadian data are also compared with the excellent re-refined

base stock data generated by the U.S. Army for an EPA study [2], also summarized for this

report. In addition, summarized data generated by NRC on three re-refined base stock samples obtained from an Indian company in 1977-79 are also compared. These base stocks were obtained

from diesel engine oil drainings by the acid/clay process and are destined for reuse in re-refined diesel engine oil formulations. India has a specification standard for re-refined

diesel engine oil [3]. Table 1. Canadian re-refined base Table 2. Virgin base stocks-reference,

stocks-acid/clay. Evaluation period 1968-1979

Re-ref i ner Samples

A 2

B and C 1 each

D 3

E and F _6 each TOTAL 19

In addition "D" submitted an imcompletely

re-refined base stock and "F" submitted a base stock obtained from used RR diesel engine oil drainings custom re-refined for reuse for the same purpose.

Base stock used in engine oils* - 3 samples White oil - 1 sample

base stock in MIL-L-5306 - 1 sample

*Base stocks obtained from Canadian and Mid-continent crudes by solvent refining. Summarize data from the testing

of these three oils, i.e., excluding white oil and 5606 base oil data, are shown in the various tables as "virgin". White oil and 5606 base oil data are identified separately, e.g., table 17. As might be expected, emphasis by the NRC laboratory has been placed on determining in

a general way the presence of any remaining solid and liquid used oil contaminants, oil and additive deterioration products normally present in used oils, and additives. Covered as well in a general way are process contaminants, i.e., strong acid and clay.

Figures in brackets indicate the literature references at the end of this paper.

109
No attempt was made to determine the ultimate destination of the Canadian re-refined

base stocks originating from used engine oil drainings. Many end up as RR car journal box

oils [4], but many also are formulated, it is believed into engine oils, hydraulic oils and industrial oils. The degree of formulation is also uncertain.

2. Test and Analytical Data

A variety of standard ASTM and other physical and chemical tests were performed on the oils aimed at assessing (a) levels of solid and liquid contamination, and residual additive,

(b) general physical and chemical properties, (c) hydrocarbon types and elements, (d) light, storage and low temperature stabilities, and (e) response to anti-oxidants. Results of these tests are presented in NRC, Division of Mechanical Engineering Report ME-75. In order

to keep the volume of data compact for this NBS presentation the individual results were averaged or ranges derived from the nineteen Canadian re-refined oils tested, three virgin

oils and three Indian oils (tables 3 and 6). A number of extreme results were trimmed off

to give a less misleading indication of range than by leaving them in. These trimmed off

(or removed) results amounted to no more than a few in any particular property. The U.S. ranges were similarly trimmed. Because the single RR base stock sample (obtained from used naphthenic RR diesel engine oil) showed an unusually high solids level of 47 mg/100 mL (table 3) and strong acids (table 6) a repeat sample was obtained. The repeat sample showed

a much lower solids level and nil strong acids, data more characteristic, it is believed, of re-refined RR diesel engine oil base stocks. It is believed that the contaminants were inadvertently picked up in the process. During the course of the evaluations an opportunity presented itself for checking base stock consistency on two occasions: once when re-refiner "E" submitted six samples over a span of six months in 1967, and later when re-refiner "F" submitted six samples over a span

of 10 years. The ranges of results are given in tables 4 and 7. From the data generated, and based on low levels of solid and liquid contaminants as well as low levels of residual oil additive, suggested property limits were generated to represent what would probably be regarded as good quality Canadian re-refined oils from service station oil drainings (tables 5 and 8). These, of course, are somewhat arbitrary

and not based on any end-use requirements. Bearing end-use in mind, some limits are not needed or should be relaxed while others may be needed or existing ones tightened. Some obviously would be redundant. For example, a limit for the ash content could do away with

the need for limiting metallic elements, and a sulfur limit could become unrealistic as higher sulfur crudes emerge.

In tables 9, 10, 11, 12, and 13 some comparative data are given for partially

re-refined and fully re-refined base stocks. Even though nonadditive oils, i.e. base stocks, are rarely recommended for modern machines and engines, except possibly where the

oil experiences a short duration of use, it is believed that nonadditive oils are on the market. Indeed, API service classification SA for nonadditive oils still exists and so do SA engine oils. Accordingly, a number of standard bench oxidation tests were performed on some of the base stocks. Results are presented in tables 10 to 13. In addition the L-38 engine test was performed for 10 hours on a re-refined base stock. It was not possible to run the test for the standard 40 hours owing to heavy oil oxidation and high bearing weight

loss even after 10 hours (table 14). From these data it is inconceivable that an SA engine

oil, i.e., a base stock, could perform satisfactorily for a significant period of time in an engine. Probably the API SA category should be withdrawn unless convincing evidence can

be provided to support good behavior. It is interesting to note that of the two virgin

base stocks tested one showed superior bench oxidation stability at 400 °F, but inferior stability at 200 °F while the other was vice versa (tables 10 to 13). Of more interest is the response to anti-oxidants. For this ASTM D943 was selected rather arbitrarily, because even though long in test time it does not require a dispropor- tionate amount of operator time and does provide at least some comparative data for this

study. The two additives used were zinc dialkyldithiophosphate and 2, 6-di tertiary-butyl

para-cresol. Averages and ranges are presented in tables 15 and 16. Some of the other data are shown with oxidation lifetimes (D943) in table 17 in an at- tempt to view possible correlations with oxidation lifetime. As shown a number of properties

110
of Canadian oils seem to correlate, e.g., hydrocarbon types, viscosity, sulfur, total acid number and carbon residue, although it is not known precisely which ones are operative in each instance. Furthermore, the Indian oils present some contradicting evidence, e.g., high aromatics and high sulfur contents have not hurt the oxidation lifetime. Obviously,

any real correlation would have to be based on more detailed analyses of hydrocarbon types than by ASTM D2007. For example, polar and/or sulfur compounds may enhance or inhibit the additive role. Just knowing the total amounts of one or the other is not enough; the actual active compounds may have to be identified. Suggested correlations are also shown in table

18 between demul sibi 1 ity and polar constituents as measured by the general or total type tests of polar compounds, total acid number and saponification number. Here, too, better

hydrocarbon, element and compound characterizations are needed for correlations. Three storage stability tests (one year) were performed: 1) light stability in a clear

glass bottle in the laboratory in sunlight, 2) room temperature stability in a dark bottle

in a cupboard, and 3) low temperature stability in a dark bottle in a cold room at 40 °F. In the light stability test re-refined base stocks tended to develop flocculent precipitates

after about 3 months in the sunlight; the virgin stocks tended not to even after one year

(this includes the white oil and MIL-L-5606 base stock). This generalization has to be interpreted with care, however. Re-refined base stock from one of the re-refiners (one sample) did not precipitate; some recent samples of virgin base stocks are showing evidence

of precipitates that settle. Re-refined oil flocks tended not to settle.

In respect to room temperature stability, no samples either re-refined or virgin showed flocculation even after one year. In respect to low temperature stability, the re-refined

base stocks developed precipitates at 40 °F while the virgin base stocks did not. IR spectra of a representative number of the oils were obtained. These are presented

in figure 1 and the following observations are made about a number of the peaks:

o Peak at 1710 cm"1 due to carbonyl absorption of some engine oil additives. Barely present in Canadian re-refined engine oil base stock and RR re-refined

base stock. Absent in the others. Carbonyl absorption also results from oil oxidation.

o Peaks at 1600 cm

-1 and 813 cm

-1 due to double bond of aromatic hydrocarbons. Absent in white oil and MIL-L-5606 base stock. Present in all others in varying degrees.

o Peak at 720 cm

-1 due to saturates. Present in all samples. Cycloparaff ins tend to absorb at higher wave numbers, e.g., 745 cm

-1

. The broader peak of the MIL-L-5606 base stock 720 cm 1 and up could be characteristic of cyclo- paraff ins.

3. Summary

In summary, the Fuels and Lubricants Laboratory of NRC (Canada) has been examining

for over 10 years, as a service, the properties of base stocks made by Canadian re-refiners. Nineteen samples of acid/clay processed base stocks from six Canadian re-refiners were

examined.

As shown, when well re-refined, the base stocks have excellent properties including a good response to anti-oxidants and a high degree of cleanliness. Since traces of additives

and/or polar compounds do remain, the quality of the base stocks is judged to be slightly

inferior to that of comparable virgin refined base stocks. Some suggested specification limits for various properties and some indication of batch-to-batch consistency were obtained. Any usage of the limits should be done with

caution, e.g., sulfur, bearing in mind the rapidly changing crude oil picture and engine

and machine technology leading to oil products of differing compositions. Certainly

modifications are in order; it may even be desirable to have grades of base stocks.

Ill
4. Recommendation

ASTM standards are absent in some areas and some ASTM standards are inadequate. For ex- ample, good ASTM standards are needed for detecting metals and non-metals in low ranges. Ash

(D482) and sulphated ash (D874) methods could be extended to lower levels of detectability. Qualitative tests for appearance and odor would be useful. An ASTM standard specification

could even be developed for re-refined base stock quality, if only to limit the levels of used

oil contaminants, additives and process materials. There could even be a number of grades.

Microns

Wavenumber (cm'1

)

Figure 1. IR spectra of several base stocks.

No. 1 - White oil No. 4 - Virgin base stock

No. 2 - MIL-L-5606 base stock No. 5 - Canadian re-refined base stock

No. 3 - Virgin base stock No. 6 - Indian re-refined base stock

No. 7 - RR re-refined base stock

112
Table 3. Physical properties - ranges/averages.

Gravity & viscosity

API gravity (D287) Viscosity index (D2270) Viscosity at 210 °F (D445) cSt

SAE

R.R.(l) 26.1[25.5]

79[79] 14.5[14.9]

40[40]

CANADA

Re-refined U.S. 29.1-30.2

100-113

7.2-

20

28.5-30.5

97-110 6.6-9.3

20

27.4-27.6

102-104 11.2-11.4

30 Solid contaminants & ash Trace sediment (D2273),% V .001 .000 .000-. 005 Solids (D2276), mg/100 mL 47[6] 0.5-3.5 3.3-5.0

Ash (D482), % W .002[.000] .000 .000-. 01 Sulfated ash (D874) % W .004 .000 .001-. 01

Rams. carb. res (D524), % W .27 .05-. 07 .12-. 19

.004-. 06(2) 3.1-6.0

.000-. 004

.000-. 004

.24-. 26

Flash point (D92), °F 480 395-450 400-450 410- 450 420-470

Dilution (D3525), 3i V (8) .02[.25] .00-. 02 .03 .01-. 03 Glycol (D2982) Nil Nil Nil Nil Water (visual) Nil Nil Nil Nil Distillation range (3) IBP, °F 670[522] 605-675 540-615 520- 680 550-630

5%, °F 780[741] 675-715 655-690 690- 725 640-725

50%, °F 890[779] 785-805 780-810 825- 870 830-920

90%, °F 940[885] 860-880 860-970 990- 1060 940-1085

95%, °F 940[988] 875-905 875-1030 (4) 950-1110

FBP, °F 960[1037] 910-970 940-1080 (4) 970-1135

Miscel laneous ASTM color (D1500) D8.0[8.0] <0.5 2-5 Aniline point (D611), °F 227 210-225 222-226 Copper corrosion (D130) No. 1 No. 1 No. 1 Odor (5) (6) (5) Appearance Dark (7) (7) Cloud point (D2500) °F 0 -2 to +12 +12 to +24

Pour point (D97), °F +20 -5 to +10 -25 to +10

2.5-6.5 220-225

No. 1

3-L4.0 226-230

No. 1 (5)

(7) +45 to +50

+45 to +50

(1) Data obtained on only one sample received in December 1976. Data on another

sample received in November 1979 are given in [ ]. (2) The three samples had results as follows: .004, .004, and .06% V. (3) Distillation range obtained by G.C. ASTM D2887 generally followed for Canadian

and Indian samples. Some difficulty was experienced at the end point when over

1000 °F. Comparisons with vacuum distillation data suggest that in this instance

the G.C. end points may be low. The U.S. procedure of cutting off the distillation at 600 °C (1112 °F) and recording the residue at this point seems preferable.

(4) Residue range at 600 °C (1112 °F) is <1 to 6% w. (5) Odor characteristic of oils obtained by acid/clay re-refining.

(6) Odor characteristic of virgin or refined oils, i.e. slight oil odor.

(7) Clean, clear.

(8) Less than .05% V is regarded as nil.

113
Table 4. Physical properties - consistency of re-refined base stock. Re-refiner "E" Re-refiner "F"

No. of samples 6 6 Period, years 1/2 (1967) 10 (1968-78) Gravity & viscosity

API gravity (D287) 28.8-29.5 29.1-29.9 Viscosity at 210 °F (D445) cSt. 8.6-9.4 7.3-8.2 Viscosity index (D2270) 101-104 97-102

Solid contaminants & ash Trace sediment (D2273), % V .000-. 004 .000-. 001 Solids (D2276), mg/100 mL Ash (D482), % W .005-. 03 .000

Rams. carb. res. (D524),%W .12-. 24 .11-. 17 Liquid contaminants

Flash point (D92), °F 440-460 390-440 Dilution (D322), % V Nil Nil Glycol (D2982) Nil Nil Miscellaneous

Color (D1500) L3.5-L6.5 L2.0-3.5 Copper strip corrosion,

3 h at 100 °C No. 1 No. 1 Aniline point (D611), °F 225-117.5 222-226
Table 5. Suggested limits for well re-refined Canadian base oils. (Acid/clay processed from service station drainings)

TEST Gravity & viscosity

API gravity at 60 °F Viscosity index Viscosity at 100 °C Solid contaminants & ash Trace sediment, % V Solids, mg/100 ml_ Precipitation no. n-Pentane insol . , % W Ramsbottom carbon residue % W

Ash & sulfated ash, % W

Physical Tests METHOD

D287 D2270

D445

D2273 D2276

D91 D893/B

D524 D482/D874

SUGGESTED LIMITS 28.5-30.5

95-115 9.0-9.4

.001 max

5 max

.001 max

. 02 max

.20 max

.005 max

Liquid contaminants

Flash point, °F Dilution, % V Dilution, % V Glycol Water, % VD92 D3525

D322 D2982

D95

400 mi n 0.05 max

Nil

Nil

Nil Workmanship

Appearance

Odor Color

Visual

Smell D1500

Clean, clear

Characteri stic 4.0 max

Miscel laneous Copper strip corrosion,

3 h at 100 °C Aniline point, °F Cloud point, °F Pour point, °F Distillation range, °FD130

D611 D2500

D97 D2887

No. 1 220-226

+24 max +15 max 550-1100 (1) Note: (1) Or in lieu of 1100 °F max. temperature, a limit on residue at 600 °C of 5% W max

115
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116
Table 7. Chemical properties - consistency of re-refined base stock.

Number of samples

Period, years Neutralization & saponification numbers

Total acid No. (D664)

Total base No. (D664) Strong acid No. (D664 Saponification No. (D94) Initial pH reading (D664) Hydrocarbon types (D2007) Saturates , % W Aromatics , % W

Polar compounds, % W

Miscel laneous Sulfur (D129), % W

Nitrogen, ppm (2) Molecular weight (D2502) Metallic elements (AA)

Re-refiner "E" 1/2(1967)

.12-. 37

.00-. 01

Nil

.09-. 22 479-496

Re-refiner "F" 10(1968-78)

.04-. 20

.00-. 09

Nil

75.9-78.0

20.3-22.2

1.6-2.2

.08-. 21 5-33 448-475

<5 (1) NOTES: (1) Each element. Element tested were: Al , Ba, Ca, Cr, Cu, Fe, Mg, Pb, Si, and Zn. (2) Determined by Canadian Ministry of Energy, Mines & Resources by microcoul ometry. Suggested specification limits for well re-refined Canadian base oils. (Acid/clay processed from service station drainings)

Chemical tests TEST Neutralization and saponification numbers

Total acid no. Total base no. Strong acid and strong base no. Initial pH reading Saponification no. Hydrocarbon types Saturates , % W Aromatics, % W

Polar compounds, % W

Metals & silicon

Calcium, barium, ppm

Zn, pb, Mg, Cu, Cr, Fe, Na, ppm

Silicon, ppm Non-metals

Sulfur, % W Nitrogen, ppm

Chlorine, ppm (2) Phosphorus Oxygen

Response to anti-oxidant

Oxidation with 0.3 % w DBPC, hrs

D664 D664

D664 D664

D94

D129, D1552

D1317 D1091

SUGGESTED LIMITS 0.20 max

0.10 max

Nil 6-8

1.0 max 75-80

20-22

2.5 max

10 max

5 max

10 max

0.20 max

100 max

50 max

15 max

0.60 max

(1) Each element.

(2) Includes bromine; ASTM D1317 measures halogens. If a standard test detecting lower limits is available the chlorine limit could be lowered to 20 ppm. 117
Table 9. Properties of partially vs fully re-refined base stocks. Partial- Full-range of single results (from

sample3 tables 3 & 6) Color (D1500) D8.0 2-5 Trace sediment (D2273), % V 0.8 .000-. 005 Sulfated ash (D874), %w .176 .001-. 01 Total acid No. (D664) .28 .06-. 24 Polar compounds (D2007), % w 5.1 2-4 Saponification no. (D94) 1.0 .07-1.2

Zinc (AA), ppm Much <l-8

Lead (AA), ppm 350 <1-12

Iron (AA), ppm 23 <1~18

NOTE: (a) Submitted by re-refiner "D" (table 1).

Table 10. Oxidation of base stock at 400 °F (B.A.M.

a-IP48). Viscosity Carbon

0 Ratio8 Residue Increase Re-refined (fully) 1.4 0.9 Re-refined (partially) 2.0 1.8 Virgin, base stock 1 1.3 0.4

Virgin, base stock 2 .1.9 1.0 CGSB Specifications (old requirement)

3-GP- 51(non-heavy duty engine oil)® 2.0 max 1.1 max9 3-GP-100(aircraft recip. engine oil) 1.75 max 1.1 max9 NOTES: a B. A.M. is the British Air Ministry Oxidation Test IP48.

b Ratio of viscosities at 100 °F; after oxidation divided by before

oxidation.

c Difference in Ramsbottom carbon residue; after oxidation minus before oxidation.

d CGSB is Canadian Government Specifications Board, Ottawa.

e 3-GP-51 was a specification for a gasol ine/diesel engine oil (SAE 20). It was cancelled in 1966. No engine sequence

tests were required although a performance test was indica- ted as "may be required".

f 3-GP-100b is non-detergent reciprocating aircraft engine

oil comparable to MIL-L-6082. The requirement for the B.A.M. test was dropped in 1966 when 3-GP- 100c was issued.

g Assuming that the new oil carbon residue is .1. The limit is stated as original +1.

118
Table 11. Oxidation of base stock at 200 °F (ERDA-modi f ied D943)

a

. Sap.

Re-refined (fully) 5.9 0.7 0.6 Re-refined (partially) 53.4 0.4 1.4 Virgin, base stock 1 81.2 2.4 0.3 Virgin, base stock 2 1.5 5.3 0.0

NOTE: (a) Test developed by DOE, BETC (ref. 5).

Table 12. Oxidation of base stock at 200 °F (CIGRE-IP 306). Tota 1 Oxidation Products

Re-refined (fully) Re-refined (partially)

Virgin, base stock 1 Virgin, base stock 2

NoCatalyst

0.1

0.3

6.6

0.0

Solid Soluble Catalyst Catalyst

2.4 3.3 17.6

0.7 15.7 2.2

Table 13. Oxidation of base stocks - comparison of data' Test Virc in Re- refined

Temp. , °F Base 1 Base 2 Fully Partially

B.A.M. (Viscosity ratio) 400 1.3 1.9 1.4 2.0

ERDA (Filt. res.) 200 81.2 1.5 5.9 53.4

CIGRE (Tot. oxid. prod.) 200

No catalyst 6.6 0.0 0.1 0.3 Solid catalyst 17.6 0.7 2.4 3.3 Soluble catalyst 15.7 2.2 1.9

NOTE: (a) Data taken from tables 10 to 12.

Table 14. Oxidation of base stock - re-refined base stock. L-38 engine test (10 hours) Bearing weight loss, mg 430

Total acid no. (oxidized oil) 13 Viscosity increase, % 62 Hydrocarbon types (oxidized oil) (D2007) Saturates, % W 52 Aromatic, % W 19 Polar compounds, % W 28 Infrared analysis (oxidized oil) (a) Note: (a) Strong peak at 1710 cm 1

. 119
Table 15. Response to anti-oxidants-ranges.

ASTM D943, lifetime-hours

RR 336(168)" 504(336)c Re-refined 336-1512 1008-2016 Virgin (reference) 840-2016 1680-2325 White oil <2016 <2016

Base stock MIL-L-5606 <3024 <3024

Notes: (a) DBPC is 2 ,6-ditertiary-butyl para-cresol

.

(b) ZnDP is zinc dial kyldithiophosphate.

(c) Data on recent sample shown in parenthesis.

Table 16. Response to anti-oxidants-consi stency ASTM D943, lifetime-hours. Re-refined base stock, supplier "F" 0.3%w DBPC

3 0.5%w ZnDPb Sample A 504 1008 Sample B 504 840 Sample C-test 1 672 1176 Sample C-test 2 672 1008 Sample D 504 840

Notes: (a) DPBC is 2,6-ditertiary-butyl para-cresol.

(b) ZnDP is zinc dial kyldithiophosphate.

120
121
Table 18. Demul sibi 1 ity (D1401) vs polar constituents.

Base stock

Demul sibi 1 ity D1401

Polar CPDS D2007T.A.N. S664Sap. No. D94 Re-refined 1 40-40-0 (15) 1.9 0.11 0.5

Re- refined 2 40-39-1 (35) 1.6 0.11 0.12 Re-refined 3 40-31-9 (60) 1.9 0.12 0.28

Re- refined 4 22-0-58 (60) 2.7 0.06 0.96 Re-refined R.R. 0-0-80 (60) 2.5 0.27 0.48 Virgin base stock 1 40-40-0 (7.5) 0.7 0.07 0.66 Virgin base stock 2 40-40-0 (5) 1.0 0.03 0.2

The author gratefully acknowledges the permission granted by Mr. E. Dudgeon, Director

of the Division of Mechanical Engineering and Dr. R. B. Whyte, Head, Fuels and Lubricants

Section, and the efforts of the staff in performing the tests. References

[1] Strigner, P. L. , Moroz, G. , Sabourin, R. , Burton, G. , and Bailey, T. , Properties of base stocks obtained from used engine oils by acid/clay re-refining, NRC DME Report ME-75 (1980).

[2] Frame, E. A. and Bowen, T. C. , Jr., U.S. Army/Environmental Protection Agency Re-refined Engine Oil Program, AFLRL Report No. 98. [3] Indian Standard Specification for Re-refined Automotive Internal Combustion Engine Lubricating Oils, IS: 9048-1979 (May 1979).

[4] Strigner, P. L. , MacLeod, D. M. , Dunn, T. R. , and Shepp, L. P., Properties of USSR,

U.S.A. and Canadian R.R. Car Journal Box Oils, ASLE No. 79-AM-6E-2, presented at 34th Annual ASLE Meeting, St. Louis, MO (April 30-May 3, 1979).

[5] Whisman, M. L. , Goetzinger, J. W. , and Cotton, F. 0., Waste lubricating oil research;

an investigation of several re-refining methods, Bureau of Mines Report RI 7884 (1974).

122
National Bureau of Standards Special Publication 584. Proceedings of Joint Conference

on Measurements and Standards for Recycled Oil/Systems Performance and Durability held at

NBS, Gaithersburg, MD, October 23-26, 1979. (Issued Nov. 1980) ASSOCIATION OF PETROLEUM RE-REFINERS STANDARDS FOR RE-REFINED BASE OILS

MORCO/APR

7601 W. 47th Street

McCook, IL 60525 About 1950 the members in the Association of Petroleum Re-refiners (APR) felt that they should have a set of standards or specifications for re-refined base oils which could in some way be used as a requirement for active membership. The purpose was, of course, to improve

the re-refiners image, at least the image of the members of the APR. The specifications were written for oils of SAE, 10, 20, 30, and 40 grades and included viscosity limits, minimum

flash points and maximum colors. They then added to the membership application a statement

that those applying for active membership are regularly engaged within the United States in the business of re-refining used oil and operating a plant with the capability of meeting the technical requirements of re-refining oil in accordance with the minimum standards of APR.

In 1961 the standards were rewritten as shown in table 1. The purpose was to improve

the quality of re-refined oils produced by the APR membership. The changes made included raised minimum flash points, lowered maximum colors and, in addition, the setting of maximum

total acid numbers, moisture content, ash content and precipitation numbers. Association of Petroleum Re-Refiners standards for re-refined oil motor oil base - SAE 10 to SAE 40. Any re-refined base oils , whether motor oils, hydraulic oils, etc., must conform c to these specifications, except where customer specifications are applicable. Viscosity @ 210 °F Minimum Flash °F Maximum Color

SAE 10 40-45 365 3.5 SAE 20 45-58 385 4.5

SAE 30 58-70 430 5 SAE 40 70-84 450 6 Minimum Viscosity Index - 90 Difference Between Flash Point and Fire Point - 40 °F min Neutralization Number - 0.15--Strong Acid Number - 0.0

Ash - 0.01% maximum

Moisture - trace Precipitation number - 0.0 ASTM Test Designation

Flash Point - D-92 ASTM Color - D-1500 Saybolt Viscosity - D-88a Viscosity Index - D-567 Neutralization Number

Strong Acid Number

Ash - D-482 Precipitation Number - DD-974 or D-664

It is preferable to determine kinematic viscosity by ASTM Method D-445 and convert to Saybolt viscosity using ASTM Method D-446.

123
In the fall of 1977 the APR Board of Directors asked me to revise the standards. Before making a revision, consideration was given to the areas in which re-refined oils were being discussed and studied. A partial list includes the NBS Recycled Oil Program, the NBS con- ferences, APR conferences, the involvement of ASTM, and the MERADCOM effort in revising the MIL L 46152 specification. These have all presented the need for more technical data about

re- refined oils. After the development of data showing adequate quality of product, there must also follow

the assurance that equally good quality control will exist in the industry. In order to bring

about this control, I felt that a set of test methods useful for determination of base oil quality was needed. The suggested program for control was presented to the APR for their

approval as shown in tables 2, 3, and 4. The type of contaminant present in used oils is shown following its specific test method and this is followed by a suggested limit for re-refined base oil. In table 5, a typical analysis of current stock automotive crankcase drainings is shown to point out the need for each specific test method. These test methods

and the limits set may need some changes to allow for the various re-refining process in existence and possible plant equipment variables not readily foreseen. Table 2. Association of Petroleum Re-Refiners proposed quality

control requirements for re-refined base oil. The following test methods were selected to evaluate

the effectiveness of re-refining process technology

in removing contaminants present in used oils and to provide a testing program for base oil quality

assurance.

Table 3. Proposed quality control requirements. Test Method ASTM Method Contaminants Limits Flash D-92 Fuel & solvent Same as virgin, e.g.,

SAE 20 = 210 °C (410 °F) min Pentane insolubles D-893 Insolubles (Dirt, 0.01% wt.-max. process clay, etc.

)

Ash, sulfated D-874 Metal 0. 01% wt. -max. Glycol D-2982 Anti-freeze Negative

Sulfur D-2552 Additive 0. 25% wt. -max. D-129 Phosphorus Additive 50 PPM - max. Chlorine Additive 100 PPM - max. Neutralization D 664 Polar materials Tan 0.15 - max. number (acids, alkalis) strong base-0.00 max. strong acid-0.00 max. Moisture 0. 01% wt. -max.

124
Aniline point Viscosity

40 °C/100 °F Viscosity

100 °C/210 °F Viscosity index Gravity API

ASTM Method

D-611

D-445

D-2270

D-287

Contaminants

Aromatics

Limits

200 °F - min

VI - 90 min

Spectrograph^

Trace metals X-ray fluorescence

atomic absorption

emission

Metal contaminants

from additives,

wear, etc.

Total all elements

<200 ppm

Table 5. Analytical data - used automotive crankcase oil. Flash point °F 250 Pentane insolubles % wt 2.9 Ash, sulfated % wt 1.8

Glycol (antifreeze) Present Sulfur % 0.55 Phosphorus PPM 800 Chlorine PPM 3500 Moisture % volume 8.0 Viscosity SSU @ 100 °F 310 Viscosity SSU @ 210 °F 57.45 Viscosity Index 130 Gravity API 27.0 Spectrographic - PPM Copper 40 Aluminum 45

Iron 320 Silicon 100 Lead 3950 Zinc 740 Manganese 35 Boron 25 Calcium 1420 Sodium 120 Barium 70 Magnesium 350

The Board of Directors of the APR has not taken a position on this proposed quality

control program at this time. At the next opportunity, I will urge the APR Board of Directors

and APR membership to consider the acceptance of this program as a major step forward in making the re-refiners products more readily acceptable in the marketplace.

125

National Bureau of Standards Special Publication 584. Proceedings of Joint Conference

on Measurements and Standards for Recycled Oil/Systems Performance and Durability held at NBS , Gaithersburg, MD, October 23-26, 1979. (Issued Nov. 1980)

THE VISCOMETRIC REQUIREMENTS FOR RE-REFINED ENGINE OILS Theodore W. Selby

SAVANT, Inc. 234 E. Larkin Midland, MI 48640

The following paper is intended for a reader less than familiar with:

1) the viscometric relationships between the base stock and formulated en- gine oil, and 2) the demands of the modern automotive reciprocating engine

on the viscometrics of the lubricant. Hopefully, the views and information

to be brought forth will, to some degree, clarify a complicated area domi- nated by a complex property of lubricants--the viscosity.

1. Introduction

For as many years as the automobile has existed as a commercial device there has been

some degree of cooperation between the auto manufacturers and those responsible for formulating engine oils. The level of cooperation has waxed and waned over the years but over the

last twenty or thirty years such interaction has grown more intense as the automotive ma- chine itself has grown more complex and more demands have been placed on the engine. The

fact that the automobile engine is totally dependent upon its lubricant is a rather basic

fact. However, the fact that the automobile engine can work reasonably well with a rather

wide range of engine oil quality, at least for a limited time, is a more important fact. It

is important because the differences between engine oils of high quality and those of inferior grade only become evident after a period of usage. Marked differences in engine oil may

well be reflected in differences in engine performance or condition in as little as two or three months of casual driving but, of course, by then a poor choice of engine oil has left

an indelible mark on the engine. Thus, it is no surprise that the automotive industry's efforts to produce higher-performance, reduced-maintenance, long-lived vehicles has focused

strong attention not only on the design, metallurgy and fabrication of the engine, but also

on the lubricant qualities.

At the heart of the interaction of the automotive and oil industries is the joint concern about responsibility for acceptable engine performance or the occasional engine

failure. In the latter case, it is often difficult to distinguish the cause for engine

failure particularly if it is sudden and catastrophic. Sharing such a burden does not necessarily make it more pleasant—particularly if there is a niggling suspicion that the other fellow has not used his technical "smarts". To meet this need for cooperative

technical progress in the care and feeding of the automobile engine, the Society of Auto- motive Engineers (SAE), the American Petroleum Institute (API) and the American Society for Testing and Materials (ASTM) have jointly established performance limits for engine oils, called the "engine sequence tests". These tests have been, in one respect or another, on

the American scene for a little over twenty years and the tests have thus far shown their

value in providing the motorist with a relatively clear label of quality wherever he goes. These tests, however, are performance-based and expensive to run. They do not tell why

an oil is or is not successful in passing the test but only that it, in some way, failed to meet the test criteria. For those engineers interested in screening materials or in running preliminary tests on batch blends, other faster, less time-consuming and expensive tests are very desirable. Development of such tests are presently concerning several individual laboratories and collective groups. Today there are two new directions that are opening for those concerned about the development and formulation of engine oils. One is the desire to produce fuel-efficient

127
engine oils and the second is the desire to provide re-refined base stocks for the blending of engine oils. Related to these two areas of development, viscosity is the single most impor- tant element of the engine lubricating oil, the property easiest to measure and potentially

most informative concerning performance and quality of the oil; but the property of viscosity is also most likely to cause confusion and error. This paper will examine the manifestations of formulated engine oil viscosity and relate them to re-refined base stocks.

2. Overview of Viscometric Effects of the Engine Oil on the Engine Before discussing the nature and range of viscometric properties of engine oils it is desirable to briefly and generally consider the effects of engine oil viscosity on the en- gine. Details will be offered later in the paper. First of all, the lubrication of essential operating members of the reciprocating

engine is by the nydrodynamic lubrication process--a process completely dependent on the viscous properties of the engine oil. If the engine oil viscosity is, or becomes, inade- quate in providing nydrodynamic lubrication, the engine becomes a basket case —usually rather quickly. Secondly, the engine oil viscosity becomes very much higher at low temperatures and this property limits the startability of the engine. Thirdly, at low temperatures the engine oil viscosity may become so great that it limits oil supply from the oil pump to the engine. Furthermore, the engine oil may in some cases develop a gel structure at low temperature which cavitates in the vicinity of the oil pump inlet leading to air-binding of the oil pump, again limiting lubricant flow to the engine.Fourthly, at high temperatures the viscosity is affected by the chemical and physical changes or additions which occur to the engine oil as it is used. Changes, such as oxidation, or additives, such as ingested particulates, can cause the viscosity and gel-forming

tendencies of the engine oil to increase to the extent that the engine oil is actually no longer available to the engine even at moderate temperatures.

Fifthly, the viscosity is a form of friction and absorbs energy from the engine, thus reducing the engine's efficiency.

Thus, it is evident that the viscosity of the engine oil and the conditions chosen for

its measurement are very important criteria in regard to establishing the qualities of the engine oil for service. The SAE has developed and maintained the Engine Oil Viscosity Clas- sification System since 1911 in an effort to provide a selection of viscosity grades for the engine manufacturer to recommend and the vehicle-owner to purchase to meet their needs. This system is presently undergoing a major revision as new needs and technical insights

have developed.

3. The Viscosity and Viscometry of Engine Oils

3.1. Base stocks

At one time in the history of engine lubricants, what we now call base stocks were the finished engine oils. The increasingly demanding requirements of the engine and the auto- mobile owner have generated the need for modern engine oils whose base stocks may contain up to 20 percent of specialized additives. Today the base stocks provide the foundation on which the quality of the finished lubricant rests and it is, thus, very important that base stock quality be adequate for the task.

3.2. Viscometric requirements of the engine

To restate, the engine is highly dependent on the viscometric properties of the engine

oil for the following needs: 1) To provide hydrodynamic lubrication to the bearings and pistons, 2) to permit 1 ow- temperature starting, and 3) to permit pumping from the sump to the operating engine.

128
All of these properties are dependent on the composite viscometric contributions of the

base oil and the additives. To consider these briefly: Hydrodynamic Lubrication - To meet the hydrodynamic lubrication needs of the engine, the engine oil viscosity in the bearing areas must not drop below a certain value called the "critical viscosity". This value varies with the design and age of an engine but is in the range of 3 to 6 centipoise. Low-Temperature Starting - Low-temperature starting is highly dependent on the design

of the engine and the viscosity of the engine oil. Again, another "critical viscosity"

exists which may range from 2500 to 25 000 centipoise depending on the engine, the temperature, the fuel, and the battery and starter. This critical viscosity is the maximum viscosity at which a given engine will start. Pumpability - More recently, concern has been expressed about oil pump supply to the engine at low temperatures. Standard tests are now being developed by the ASTM for the

SAE to assure that future engine oils will be neither "air-binding" (i.e., structure-limited)

or "flow-limited" (i.e., viscosity-limited). (These terms, and others to come, will be more completely explained in following sections.)

3.3. Viscometric properties of engine oils

At a given temperature an engine oil may be either Newtonian or non-Newtonian in be- havior. In general, single grade engine oils (i.e., SAE 20, 30, 40, or 50) are Newtonian in behavior except at temperatures below the "cloud-point" (the temperature at which the wax

in the oil begins to come out of solution). On the other hand, most multigrade oils (i.e.,

5w-20, 10w-30, 10w-40, 20w-50, etc.) are non-Newtonian at any temperature if they possess

a polymeric Viscosity Index Improver. (However, some multigrade oils made from synthetic

oils, if they contain no polymeric additive, are likely to show Newtonian behavior.) Newtonian Behavior - A liquid is said to be Newtonian if, at the temperature of measurement, the force causing flow is proportional to the rate of flow. Shear stress (or force per

unit area under shear) can be substituted for force and shear rate (or the velocity gradient

of the fluid layers) can be substituted for the rate of flow. If this is done, the constant

of proportionality is the viscosity and the resulting equation and graphical expressions are

shown in figure 1.

t or G

A, B. Figure 1. Newtonian behavior (t = nG or q = t/G) (in which x is shear stress, q is the viscosity, and G is shear rate).

129
Newtonian behavior permits predicting viscometric response of the engine oil since, at

a given temperature, the oil has a constant value of viscosity at all shear reates or stresses as can be easily seen in figure lb. The behavior shown in figures la and lb will pro- vide contrast in the following discussion of non-Newtonian behavior. Non-Newtonian Behavior - Gelation - An oil sometimes develops a structural characteristic or is said to gel when the temperature falls near or below the pour-point of the oil (the temperature at which the oil will not flow under a mild hydrostatic head). The struc- ture is often fairly weak and can be broken up readily at relatively low shear stresses.

Still a certain amount of force is usually necessary in order to cause initial flow. This

is termed the yield stress of the fluid and is shown in figure 2. Once the structure is broken, it usually will not reform or recovers only slowly and partially if the oil is held

at the initial temperature. Thus, in contrast to figures la and lb, the curves of increasing and decreasing shear stress would look as in figures 2a and 2b. This hysteresis effect

is an identifying characteristic of gelled oils.

t = n aG + yield stress

t - rijG

H

a

: apparent viscosity of oil

H

l

: sheared viscosity of oil

A. B, Figure 2. Non-Newtonian behavior - waxy gelation. While the oil structure will not readily reform as long as the oil is held at the tem- perature at which its presence is noted, if the temperature is raised and again lowered, the structure will reappear. Depending on whether or not the gelation "memory" of the oil is erased by bringing the oil to sufficiently high temperatures, the renewed structural charac- teristics may be equal to, less than or greater than the original structure. In fact, some oils will only show structural characteristics when they have been repeatedly cycled at temperatures somewhat above the considerably below the temperature at which the oil shows incipient gelation. The problem created by such gelling tendencies in an engine oil is the development of "air-binding" in the oil pump; a condition created by the collapse of the fragile structure

above the pump inlet which then permits the pump to "snorkel" air from the surface--effec- tively air-binding the pump as shown in figure 3. Depending on the strength of the struc- ture adjacent to the air path, the oil pump may be air-bound long enough to allow serious

130
damage to the engine from lack of lubrication. Even somewhat prolonged operation under such conditions may cause such damage to the bearings that they are predisposed to fail later or

at least show a shorter life at operating temperatures.

To treat the problem of engine oil gelation, additives known as "pour-point depressants"

have been developed to lower the temperature at which such gelation occurs. These additives

are believed to, in some way, interfere with the growth of the crystalline habit of the wax present in the oil. Even polymeric additives known for their Viscosity Index improving

ability can act as pour-point depressants as shown in figure 4. Other choices of Viscosity

Index improving polymers may have little effect or actually create a more evident gelation

as shown in figure 5. Again, these polymer effects are thought to be associated with their

interaction in the development of the wax structure which in turn creates the gelled condition. In the first case it is believed to become involved in the way structure, but be- cause of molecular dissimilarity to the wax, the polymer prevents the wax crystals from fur- ther growth. In the second case, similarity between the VI Improver and the wax crystals

encourages gelation perhaps because the macromolecule is sufficiently long and flexible to serve to join two or more crystals as shown in figure 6, thus creating a wax/polymer inter- action having greater strength than the wax gel alone. In the latter case, use of pour-point

depressants will control both the wax gelation and the wax/polymer effect.

As an additional point of interest regarding engine oil viscosity, gelation, and pumpability: normally, one would think that fuel dilution of an oil would lead to lower viscosity

and this is true. However, fuel dilution of a diesel engine oil with a waxy diesel fuel can both decrease the viscosity and raise the yield stress as shown in figure 7. From the foregoing, it is evident that the gelation characteristics of the base stock,

its treatment by pour-point depressants and the effect of the VI Improver all play roles in developing an engine oil with acceptable pumpability at low temperature.

to engine

oil pump

Figure 3. Air-binding limited pumpability.

131
H a = apparent viscosity of basestock

1i = sheared viscosity of basestock

Hg = gel viscosity

^p = polymer-contributed viscosity

Hj-, = blend viscosity

n /

n g f n»

Figure 4. Gelation inhibiting polymer.

apparent viscosity of basestock

apparent viscosity of blend

gel viscosity of basestock

gel viscosity of blend

sheared viscosity of basestock

polymer contributed viscosity

after shear sheared viscosity of blend

Figure 5. Gelation contributing polymer.

132
polymer molecules

With Gel-Contributing

Polymer

Figure 6. Wax/polymer gelation effect.

G T or G

Figure 7. Effects of waxy fuel dilution on gelation of engine oil.

3.4. Other 1 ow- temperature , low-shear effects

There is another way in which pumpability of the engine oil may be restricted and this

is by being "flow-limited". At the very low shear stresses imposed by air pressure on the surface of the oil, the viscosity of the engine oil is simply too high to supply the oil pump with sufficient oil and the pump and engine are "starved" for lubricant. This ~ dition is shown in figure 8. The critical viscosity for a "flow-limited" condition is different for each engine but values of 30 000 centipoise are being considered as an SAE

limit. 133
Figure 8. Flow-limited pumpabi 1 ity. The "f low-1 imited" characteristic of an engine oil is highly dependent on the viscosity- temperature relationship of the base stock as modified by the pour-point depressant.

3.5. Non-Newtonian effects of VI improvers (and other polymeric additives) Originally, VI Improvers were developed as engine oil additives to formulate oils of improved viscosity-temperature characteristics and this is still their most important function although they now also serve as ashless dispersants and pour-point depressants.

A polymeric VI Improver is a long-chain macromolecule in oil solution as schematically

represented in figure 9a. At low shear stresses it interferes most effectively with the molecular motion of the much smaller oil molecules, thus increasing the viscosity of the mixture by its presence. At higher shear stresses some of the polymer effectiveness is lost and the viscosity of the formulated oil decreases. Figure 9b shows this form of temporary viscosity loss (TVL) caused by orientation of the polymer coil under the shearing

forces. If these shear stresses grow still more intense, the polymer molecule can be rup- tured, as in figure 9c, forming two more or less similarly sized macromolecules which are collectively less effective in controlling the flow of the oil molecules than their single macromolecular precursor. An oil which experiences such polymer degradation experiences an irreversible change--a permanent viscosity loss (PVL). The effects of either temporary or permanent viscosity losses can be very significant depending on the molecular weight of the polymer and, thus, its susceptibility to distortion

and rupture. This can be shown by some work by Stambaugh and Kopko in figure 10. Here it

is evident that up to 60 percent or more of the viscosity contributed by the VI Improver can

be "lost" (temporarily) at the shear rates encountered in the bearings depending on the molecular weight of the polymer. Choosing to use a lower molecular weight polymer, such as

VI Improver C rather than A, can reduce the temporary viscosity loss from 60 percent to 20 percent. Moreover, in regard to permanent viscosity loss, the lower molecular weight VI

134
Improvers B and C showed no permanent degradation in the engine while the higher molecular

weight Polymer A permanently lost 20 percent of its viscosity contribution while in engine

service. (The insert in figure 10 is to point out the fundamental nature of the larger plot

and to thus show the form of temporary viscosity loss as opposed to the Newtonian behavior

previously shown in figure 1.)

orientation of coil under shear forces

B, Temporary Viscosity Loss:

(TVL)

(shear rate: dv/dr)

Rupture of coil and subsequent orientation under shear forces

A, Quiescent Polymer Coil in Oil Solution

C, Permanent Viscosity Loss:

(PVL) jL if

Figure 9. Temporary and permanent viscosity losses. Obviously, the individual or combined effects of temporary and permanent viscosity loss must be considered very carefully in the formulation of an engine oil. If these effects are

such as to produce an engine oil whose viscosity in the operating bearing at high temperatures is less than the critical viscosity required by that engine, which Stambaugh and Kopko further showed could be at least as high as 3.5 cSt, the engine will suffer permanent damage

as shown in figure 11 for the upper two bearing sets. The lower two bearing sets represent

the response to oils having an adequate combination of base stock and VI Improver and, thus,

a viscosity above that which was shown critical in the engines they studied.

To restate, the degree to which the finished lubricant may, at high shear, experience

either temporary or permanent viscosity loss is dependent, among other things, on the molecular weight and concentration of the polymer. These properties of the VI Improver are, in turn, dictated by the viscosity characteristics of the base stock and the SAE grade level and

service desired.

135
Figure 10. Relationship of molecular weight to temporary viscosity loss.

3.6. Non-Newtonian high-shear/low-temperature characteristics

One of the most aggravating problems plaguing the average motorist in the colder parts

of the nation is a balky engine on a cold day. While there are many factors that affect cold-starting, the most critical is the engine oil viscosity. As previously mentioned, this problem was one of the primary factors leading to the development of VI Improvers, that is, to obtain an engine oil having sufficient protection for the engine bearings at highest oper- ating temperatures while still permitting low- temperature starting. The problem is more complex than first appears; if sufficient VI Improver is added to a base oil to give adequate bearing protection at high operating temperatures, in most cases a considerable amount of viscosity is also added by the polymer at low temperatures. This makes the proper formulation a matter of careful choice of: 1) base stock viscosity, 2) VI Improver, 3) temporary viscosity loss potential, and 4) permanent viscosity loss potential. There are types of polymers whose coils expand as the oil becomes warmer and contract

as the oil becomes colder. The mechanism by which this occurs has been explained by the solution dynamics of a polymer/oil mixture. If the oil is only a moderately good solvent

for the polymer, at lower temperature the polymer coil will contract upon itself as the solvencey of the oil decreases, at higher temperatures the coil expands since the solvent properties of the oil improves and Brownian motion further encourages such expansion. These dynamics are shown in figure 12 for such a polymer. Such polymers make it easier to obtain good high and low temperature viscometric properties. However, such VI Improvers may not be quite as efficient as the more soluble VI Improvers per unit polymer concentration in in- creasing the high temperature viscosity of the engine oil. Again, it is evident that the base stock plays the major role in determining which and how much VI Improver is chosen.

4. General Discussion and Summary

The foregoing has been an effort to show how important the various aspects of engine

oil viscosity are to the engine. Hopefully, it has also shown how important the visco- metric characteristics of the base stock are to the viscosity of the formulated engine oil.

136
137
In regard to re-refined base stocks and the engine oil formulated from these re-refined

stocks, viscometric analyses at both high and low temperatures with suitable instruments

permit: 1) Establishment of a consistent base stock product, 2) establishment of the op- timum selection of additives, and 3) consistency in the finished formulation.

For example, the variation which may be observed in the yield stress at a given low temperature can be related to the type and quantity of pour-point depressant. This can

be a much more sensitive and technically less demanding approach than the accrual determination of the pour-point. Similarly, the effect of VI Improvers and/or various admixtures

of synthetic base oils can be studied at both high and low shear stresses to determine the optimum formulations for a given SAE multigrade level. The response of a given base stock to oxidation tests or to field performance can be very sensitively followed by viscometric measurements, particularly when coupled with

other analytical techniques. (However, this area brings in a further complement of visco- metric analyses which are beyond the intent of this paper.)

Thus, the formulation of an engine oil to meet the needs of today's high-performance

engines requires careful understanding and close control of its viscometric properties.

Base stock properties, whether from re-refined or refined sources, are the foundation of the formulated oil and the delineator or the oil's success in meeting the engines' viscometric

needs. Since, of all the engine oil, and the one most easily and directly measured with proper equipment, there is no reason why any finished oil, properly compounded, should be deficient in this important property and its manifestations.
National Bureau of Standards Special Publication 584. Proceedings of Joint Conference

on Measurements and Standards for Recycled Oil /Systems Performance and Durability held at NBS, Gaithersburg, MD, October 23-26 , 1979. (Issued Nov. 1980)

COMMENTS FROM A PRODUCER OF VIRGIN BASE OIL

D. G. Espey

Exxon Company, U.S.A.

P. 0. Box 2180

Houston, TX 77001

In evaluating the NBS assignment against our own experiences, I am prompted to philosophize and say: "Take comfort for thy task is exceedingly difficult and don't be disheartened if you can't do the impossible."

To put your task into perspective, take a look at the massive amount of effort which

recently went into the development and standardization of the PV-1 test--which is just one engine test out of the hundreds of end-use applications for lubricating oils. Before proceeding further, let me briefly state that my company's position on recycling

oil is one of support and encouragement. We see no basic problems in reclaiming or re- refining used lubes so that they may be returned to lubricant service. Our major concern is to avoid arbitrary and unnecessary constraints which could create severe problems and substantial additional costs. The processes used in refining virgin base oils and the undesirable components removed from the raw material are different from processes used in re-refining used oils and components removed from these oils. Therefore, specifications or quality criteria applied to virgin oils may not fully apply to re-refined oils (or vice

versa). Careful consideration should be given to this matter. Since we are in complete agreement with the desire to conserve petroleum molecules in any way that is environmentally

and economically acceptable, I hope that my comments will be received as trying to describe

the real world as we see it.

I will be addressing comments to the characterization of virgin base stock quality, but before doing so, I must talk briefly about historical practices which have served consumers

well for a long, long time. Prior to the 1969/70 onset of severe domestic crude short falls, most of the virgin base stocks were produced from sweet domestic crudes, and the crude sources

and characteristics did not change frequently. Lube plants were designed and built to process

specific crudes, frequently of local origin. Although the refining processes and the crude differed from plant to plant, each plant's production was relatively constant year after year. Products would be developed and qualified and would remain qualified until some major change

occurred. But these changes did not occur overnight and requal ification programs for scheduled changes might take place over a one-to-two year period. Since about 1969, changes in crude and processing have come at increasing frequency, but they still do not come overnight, thereby giving us some time to run requal if ication tests. Since the 1973 embargo, we have had two major changes in our domestic lube base stock manufacture.

The first of these was the introduction of high sulfur, mid-east crude into our lube production circuit. This move was not without background and experience because we had several refineries in Europe already operating for years on these crudes with similar processing steps. Admittedly, these crudes were new to us domestically and represented a "change" which had to be addressed, but a technology base existed which said that good lubes could be produced from them. In another case, an extraction solvent was changed, but extensive pilot plant work preceded the plant modifications. Here again, the first application was in Europe, which provided us a data base for our conversion. In both these cases, programs were developed with the lubricants review board and the required engine test data were obtained, which showed performance equivalence in both cases.

139
However, even before the 1973 embargo, we were concerned with the rather ponderous, time consuming, and largely empirical methods for proving out the interchangeabi 1 ity of crude or process changes. Therefore, we have under way some work with the objective of developing more

fundamental relationships between lube base stock composition and performance relationships

that would be independent of crude source or processing operations. Needless to say, both sides of the equation have proved much more difficult than envisioned. The analytical or compositional portion of the studies has proceeded

satisfactorily. But the performance side is littered with an ever changing array of performance targets--gasol ine engines tests, diesel engine tests, turbine oil tests, hydraulic

oils tests, etc., and the ever present issue of additive treat and response complicates

matters.

A few years ago, most of us in this room would have picked a low sulfur, high viscosity

index base oil as optimum for formulating automotive-type crankcase oils, and yet it "ain't necessarily so." Many of the sulfur-containing compounds in high-sulfur base stocks are natural oxidation inhibitors--benef icial in higher temperature environments such as encountered in the sequence

III D test. Therefore, arbitrary limitations should not be imposed on base oil sulfur

content. Historically, viscosity index has been used as a dual measure of qual ity--i . e. , both viscometrics and oxidation stability. While VI obviously has valid meaning in many viscometric considerations, using VI as an index of oxidation stability can lead to incorrect

conclusions. Extracting a given crude to higher VI levels will generally result in a base stock having improved response to oxidation inhibitors. However, extracting different crudes

to the same VI level does not necessarily produce base stocks of the same oxidation stability-even if the sulfur levels are the same. The gross viscometric properties (VI) do not determine oxidation properties.

We surmise that many companies are attempting to quantify the relationships among all the important base stock qualities, and that new understanding will evolve from this work. Consequently, we urge you to leave open as much room as possible in your thinking and specifications for new understanding. After all, the bottom line is adequate supplies of lubricants which will lubricate equipment--not paper specifications.

140
National Bureau of Standards Special Publication 584. Proceedings of Joint Conference

on Measurements and Standards for Recycled Oil /Systems Performance and Durability held at NBS, Gaithersburg, MD, October 23-26, 1979. (Issued Nov. 1980)

CHARACTERIZATION OF LUBRICATING BASE STOCKS FOR AUTOMOTIVE CRANKCASE OILS Stephen M. Hsu Tribochemistry Group

Chemical Stability and Corrosion Division

Center for Materials Science

National Bureau of Standards

1. Introduction

Lubricating base stocks are complex hydrocarbon mixtures of paraffinic, naphthenic, and aromatic molecules [1.2] 1

. Typical structures are shown in figure 1. There are very few

"pure" molecules, and most molecules exist as mixed types. A small but important fraction

of basestock consists of molecules containing nitrogen, sulfur, and oxygen moieties. This fraction is generally more active chemically and is "polar" in nature, and has significant

influence on the performance of the lubricating oils. Some possible compounds of this class

are shown in table 1 [3]. Lubricating base stocks consist of so-called neutrals and bright stocks of various vis- cosity grades. The neutrals are generally distillates from a fractionation tower, and the bright stocks are the bottom or residual stream. Viscosities are generally measured at 100 °F in terms of Saybolt Universal Seconds (SUS). Therefore, a 120 N refers to an oil which is a distillate and has a viscosity of 120 SUS at 100 °F. Various viscosity oils are required to blend a multi-grade motor oil. Since viscosity is a function of molecular weight

and molecular size, different viscosity oils represent different molecular weight and molecular size, and to some extent, different molecular structures or molecular type distributions.

Table 2 presents some compositional variations of a lubricating stock refined from U.S. mid-continent crude (solvent extraction refining) as a function of viscosity grade. The differences are shown by the increase in polynuclear aromatics, sulfur, and nitrogen concen- trations in the fractions as the viscosity increases. Boiling point distribution differences

are shown in figure 2. The amount of sulfur, nitrogen and polynuclear aromatics are useful parameters as these compounds have a significant impact on oxidation stability, and additive

response [4-7]. At the same time the structures of these compounds are also important. Therefore, measurement of the levels of sulfur, nitrogen, and oxygen is useful only when the

crude source is kept constant after a pattern of performance behavior has been established.

2. Base Oil - Additive Interactions

In attempting to characterize lubricating base stocks for automotive crankcase oil ap- plication, let us examine how a motor oil functions. In a typical motor oil, chemical additives, excluding the viscosity index improver, comprise about 5 percent to 10 percent of the formulated motor oils. These additives are nitrogen-containing dispersants, metal-containing

detergents, rust and corrosion inhibitors, anti-wear additives, and oxidation inhibitors [8]. Generally, the additives are highly polar and functional ized molcules, which impart various

qualities that the base stocks do not possess. In the final product, the effective additive

concentration depends on the base stock- additi ve interactions (additive response) as well as additive-additive interactions. Watson [9] suggested that additives exist in oil as micelles.

The critical micellar concentration (CMC) for additives is about 10" 5 molar depending on molecular structure and alky! chain length. When several different polar species are present

in the same solution, the CMC could be altered by aggregation, reaction, and interactions of different species. The polar species can neutralize each other and reduce the total effective

additive concentration. Components originally present in the base oil, such as the nitrogen,

sulfur, and oxygen containing compounds can interfere with the micellar structures and interact figures in brackets indicate the literature references at the end of this paper.

141
Typical Structures

c-c-c-c-c c-c n-Paraffin c c - c-c-c c - c Iso-Paraffin

i i c c c-c

c ^c-c*Cv

c-c-c—— c-c Aromatic

C*CC

c

c

C cs I c^c-c'v c —c-c-c—-c Naphthene

Cn

-c' Cv

c'

C

i c c

"c*

C

"c —c-c-c-c —c Mixed

c-c

Figure 1. Typical base oil structure.

142
Table 1. Typical N, 0, S compounds. Sulfur compounds

- alkyl, cyclic and aromatic thiols

- alkyl sulfides

- alkyl, cyclo-alkyl sulfides

- cyclic sulfides Nitrogen compounds

Basic = quinolines and pyridine alkyl substituents Non-basic = pyrroles, indoles, carbozoles

Oxygen compounds

Acidic = n and branched chain acids

acids containing a cyclic group

Neutral = l-,2- or 3, and 4-methyldibenzofurans

Table 2. Base stock composition as a function of viscosity grade. 100 N 300 N 600 t Paraffins, wt. percent 22 17 17 Aromatics, wt. percent 16 24 26 Cycloparaffins, wt. percent 62 59 72 Saturates, wt. percent 84 86 74 Aromatics, wt. percent 1.5 9.6 9 Polynuclear aromatics, wt. percent 5.3 9.2 12 Sulfur, ppm 100 300 3000 Nitrogen, ppm 18 43 50 Basic nitrogen, ppm 9 28 19

wt. percent boiled off at 360 °C (680 °F) 13 2.5 2 427 °C (800 °F) 76 19.0 18 482 °C (900 °F) 98 79.0 79 538 °C (1000 °F)

15%

5%

/

\ SON

rfK 160N

<

/ I £{, 650N rTMi T iiit

Figure 2. Boiling point distri- butions of base stocks as a function of viscosity grade.

500 700 900 Temp. °F 1200°F
with the additives [10]. Some of these naturally occurring compounds have been observed

to inhibit oxidation [11]. Therefore, effective characterization of lubricating base oils depends on the ability to measure and characterize the interactions between the impurities

and additives, as well as the basic hydrocarbon molecules. There are different kinds of interactions between different additives and various

base oil polar molecules. The surface active additives such as anti-wear, corrosion, and

rust inhibitors will interact strongly with the surface active species in the base oil (such as nitrogen- and sulfur-containing compounds). The less surface active agents like dispersants will probably react with the oil-insoluble oxidation products formed under oxidation conditions. For example, aromatics are known to form oil insoluble oxidation

products through condensation reactions. Therefore, the base oil composition affects not only the initial oxidation induction behavior, but also has a significant impact during

the course of oxidation/degradation. Because of this, different base oils having dif- ferent chemical compositions may have different oxidation rates. In the presence of a specific additive package, different additive depletion rates may be observed from oil to

oil.

3. Base Oil Requirements

There are many characteristics that are desirable in a lubricating basestock. These

include the following: 1) solvency: the ability of the base oil to solubilize various

chemical additives and oxidation products; 2) oxidation stability: stability of the base

oil under oxidation conditions; 3) additive response: the extent of improvement in oxidation, corrosion, and wear characteristics from additives; 4) thermal stability: stability

of the base oil due to high temperature degradation in the absence of oxygen; 5) low temperature fluidity: the ability of the base oil to maintain fluidity under low temperatures, and 6) oil consumption: the ability of the base oil to avoid excessive volatilization under normal engine operating conditions.

All of these characteristics, at least theoretically, can be defined in terms of the physical properties, chemical properties, chemical composition, and molecular structures

of the base oils. In practice, detailed characterization of such a complex mixture as lubricating base oil in terms of chemical composition and structures is not feasible. This is particularly true since some of the characteristics can be altered with compounds

at the ppm levels. As a result, much of the previous characterization work have used the physical and chemical properties in conjunction with bench performance tests. Recent ad- vances in analytical techniques such as high resolution mass spectroscopy and high field nuclear magnetic resonance (NMR) offer new opportunities to accurately determine molecular

structures. The remaining problem, however, is to determine which structure(s) among the thousands present affects the performance characteristic. The following sections describe

each characteristic and their relations to some physical/chemical properties.

4. Solvency

The solvency of a base-oil frequently can be related to the aromatic content of the

oil. There are two aspects of solvency: one is additive solubilization, the other is oxidation product solubilization. Since some of the chemical additives are polar, the polar molecules, such as some alkyl aromatics, in the base oil can solubilize them. In some of the linear synthetic base stocks, solvency becomes a critical problem and some diesters or other polar molecules need to be added to the base stock. In solubilizing

insoluble oxidation products during use, the concept of optimum aromaticity is important

[12]. During oxidation, various organic acids, alcohols and ketones are generated. The aromatics help to solubilize the oxidation products. On the other hand, aromatics, es- pecially the polynuclear aromatics, become oil insoluble upon oxidation. Therefore, the aromatic content of base stocks should not be too high or too low. Depending on the crude source (molecular structures), processing technology, and viscosity grade, there are different optimum levels of aromatics in a base oil. Table 3 illustrates the effects of aromatics on solubilization. The solvency is measured by the spot dispersancy technique, which measures the ability of the oil to disperse sludge particles on a blotter paper and where 100 percent represents perfect dispersancy [13]. It can be seen that oil B has higher aromatic content and better dispersancy.

144
Table 3. Relation between aromatic content and solvency.

Oil A Oil B Aromatics, wt. percent 10 24 Monoaromatics , wt. percent 5 10 Paraffins, wt. percent 20 24 Spot dispersancy, percent 70 95

5. Oxidation Stability

In a complex hydrocarbon mixture, oxidation will begin when conditions for oxidation

are met for the most unstable species in the mixture [2]. Oxidation is generally accepted

as occurring via a free radical oxidation mechanism. Once the free radicals are generated,

the oxidation processes will spread to other more stable species. The oxidation stability

of a base oil may be determined by the concentration of naturally occurring chain terminating

agents such as some hindered phenols, sulfur compounds, and amines. The oxidation sta- bility of a base oil without any additive, therefore, is a measure of the level of these

agents in the base oil. Since most refining techniques such as solvent extraction, hydro- treating, and clay percolation are designed to remove the polynuclear aromatics, amines,

and sulfur compounds, it should follow that the purer the base oil, the more oxidation

unstable it becomes. This, in fact, does occur as illustrated by oils C and D in table 4. Oil D is a white

mineral oil exhaustively refined from mid-continent crude. Oil C is the same crude but

processed. In a simple air bubbling oxidation test for 6 hours at 204 °C (400 °F) without

any additives, the carbonyl concentration, C=0, measured by differential infrared spec- troscopy, shows that the white oil has been oxidized almost twice that of the conventional

oil. Table 4. Oxidation stability as a function of base stock chemical composition.

Oil C Oil D Paraffins, wt. percent 18 20 Aromatics, wt. percent 34 5 Poly-aromatics , wt. percent 8 1 Sulfur, ppm 700 5 Nitrogen, ppm 300 20 Oxidation Test

C=0, A/cm (w/o Add.) 60 100

C=0, A/cm (w/Add.) 50 50

Oil Thickening Test*

Percent Viscosity Increase 1000 10 *Test is conducted at 171 °C (340 °F) for 32 h in an open test tube with 7 percent wt. of a standard additive package. The same naturally occurring inhibitors, in the presence of chemical additives and antioxidants, may interfere with the effectiveness of the additives. Table 4 shows that

when additives were used, oxidation of oil C was reduced by 17 percent. Oxidation of

oil D was reduced by 50 percent. The same trend prevails in a more severe but longer term oxidation test where the difference in the two oils are dramatically different (1000 percent

viscosity increase at 32 hours for oil C and only 10 percent viscosity increase for oil D). Therefore, it may be generalized that the more stable the base oil (i.e., the higher

the level of impurities), the less effective the additives will be on the final product. One caution on this generalization: the measurement of the sulfur, nitrogen, and oxygen

compounds do not reliably indicate the same trend if the crude source or the processing

technology changes. Unfortunately the question of which specific structures are affecting

performance has not been answered at present.

145
6. Additive Response Additive response can be defined as the net change in performance of the lubricant which can be attributed to the additive. As has been illustrated under the section on oxidation, impurities can inhibit the oxidation process yet they can also reduce the ef- fectiveness of additives. A similar trend in the wear performance area has also been observed [14]. The effects of the impurities (S, N, 0 compounds) appear to be important

in this regard, as well as the basic hydrocarbon structures such as: aromatic to paraffin

ratio; the average alkyl chain length; and the degree and extent of branching and cyclic

structures. All of these have profound effects on the additive response. One way of looking at the additive response is that the additives represent a fixed amount of inhibition which has been determined largely by economics. Yet different mol- ecular structures have different rates of oxidation, solvency, thermal degradation, and anti-wear characteristics, that the net effect of adding a fixed dosage of inhibitor inevitably result in different degrees of performance. Of course, the additive package

itself and/or the treat level can be adjusted to compensate for the different responses.

At the current state of art, this adjustment is most often accomplished through trial and error using the engine sequence tests. This lack of basic understanding between base oil structures, additive structures, and the mechanism of their interactions is substantially

impeding technological advances in lubrication.

7. Thermal Stability

Thermal stability refers to the degradation of hydrocarbon molecules in the absence

of oxygen. The most common mechanism is carbon-carbon bond breakage under high temperatures. In heavy duty engines such as the engines used in tractors, trailers, and earth moving equipment, temperatures at the piston ring zone often reach 350-400 °C [15]. Under

these conditions, the thermal stability of the oil becomes an important parameter. Infor- mation obtained from used oil analysis indicates that the concentration of nitrates and nitrites in the used oils is sometimes twice that of carbonyl compounds. It might be speculated that because of the high temperatures, the oxidation reaction rate is extremely

fast. Oxygen is quickly depleted and the nitrogen in the presence of acidic components

from the blowby gases (S0 3 , S0 2 , H 2 0, C0 2 , etc.) reacts with the oil to form nitro and nitroso compounds. The overall stability of the lubricant depends on both oxidative and

thermal stability. In the absence of oxygen, linear alkyl paraffins is the most unstable, followed by cycl oparaf f i ns and aromatics. The thermal decomposition temperatures for these structures are approximately 316 °C (600 °F) for straight paraffins, 427 °C (800 °F) for cycl oparaf fins and over 530 °C (1000 °F) for aromatics [2]. In the presence of oxygen,

the aromatics become unstable due to the ease of substitution reactions involving the aromatic hydrogen. Sulfur compounds in the base oil also appear to have a profound effect

on thermal stability. High sulfur base oils, however, are almost always associated with

high levels of aromatics (20-30 percent by weight), and it is unclear at the present time whether this thermal instability is actually due to the sulfur and/or the aromatics. Table 5 illustrates this situation by the use of thermal decomposition data generated with

the hot tube test. In table 5, oil E is a hydrotreated base oil having the same viscosity

as oil F. Oil F is a solvent extracted high sulfur base oil. The Hot Tube test is a bench test which simulates the ring zone conditions of a diesel engine. The same commercial additive package is added to both oils, and the difference in deposit ratings is dramatic. However, identification of which specific parameter is responsible for this difference is difficult to ascertain. Possibilities include sulfur compounds, degree of saturation, aromatic/paraffin ratio, or a combination of these factors. Table 5. High temperature stability as a function

of base stock composition.

Oil E Oil F Aromatics, wt. percent 5 24 Paraffins, wt. percent 25 26 Saturated HC, wt. percent 95 75 Sulfur, ppm 300 9000 Hot Tube, 495 °F at 16 h (0-10, 10 = cl ean) 0.5 5.( 146
147
8. Low Temperature Fluidity

The low temperature fluidity is resistance of an oil to flow at low temperature,

i.e., below ~ -12 °C (+10 °F), and is directly related to the wax content and amount of linear

alkyl paraffins and their molecular weights. In a new oil, this property can be modified

and controlled by the addition of pour depressants. In service, the oxidation stability

of the oil as well as the tendencies of the oil to polymerize and to form oil insoluble products all affect the low temperature fluidity of the oil.

9. Oil Consumption

Oil consumption is oil "loss" during service, primarily due to volatility and molecular

decomposition. Oil consumption in an automotive engine can be related to the base stock volatility, the viscosities at engine operating temperatures 121-177 °C (250 °F to 350 °F),

as well as to the engine build-up tolerance between the valve guides and the valve stems. Both the viscosity and volatility can be related to the molecular weight distribution or boiling point distribution of the base stocks. Generally, the total percentage of base stocks that boil between 343-399 °C (650-750 °F) determines the base stock volatility,

and therefore the oil consumption. Oxidation stability of the base stocks also often affects

oil consumption. If a base stock oxidizes rapidly, the molecular weight distribution, and therefore the viscosity, changes accordingly. Upon oxidation, most base stocks break down

to smaller molecules, resulting in increased oil consumption.

10. Methods of Characterization Characterization methods can be classified into two categories.: measurement of physical properties and measurement of chemical properties. Most of the test methods are ASTM standard procedures and have been used by the petroleum industry for a long time. The test methods are periodically updated and revised by ASTM.

10.1. Physical properties

The important tests for physical properties of a lubricating base oil consist of the

fol lowing: Viscosity at 40 °C ASTM D-445 Viscosity at 100 °C ASTM D-445 Gravity ASTM D-287 Color ASTM D-1500

Pour point ASTM D-97 Boiling point distribution ASTM D-2887

Flash point ASTM D-92, D-56, D-93 Refractive index ASTM D-1218

Cloud point ASTM D-2500 Viscosity index ASTM D-2270 Traditionally, viscosities, viscosity index, color, and flash point are used in refineries

for quality control, particularly the viscosity index. Viscosity index is an arbitrary scale measuring the change of viscosity with temperature. The scale is based on comparing an oil to a standard paraffinic oil whose assigned viscosity index (VI) is 100, and to a standard naphthenic oil which has a VI of zero. In a way, the VI reflects the amount of paraffins

in an oil. Before the advent of solvent extraction process in lube oil manufacturing which

removes aromatics selectively, the amount of paraffins in a base oil was accepted as an indicator of quality for wear protection and lubrication. The VI also reflects the severity

of modern day refinery processes. Generally the VI is targeted between 90 and 110, depending on the viscosity grade. The significance of these tests relating to performance is not fully discussed in the various ASTM procedures. Generally, the test measures an average properties of many molecular species. Correlation between these physical properties and base oil performance char- acteristics have often not been demonstrated.

148
These physical parameters have been found to correlate with some chemical structural

information. Van Nes and Van Westen [1] cataloged various correlations between viscosities and molecular weight, refractive index and molecular structures, and developed the so-called n-d-m method. The n-d-m method correlates refractive index (n), density (d), and molecular weight (m), with percent carbon atoms in paraffinic, naphthenic and aromatic

structures. Since these parameters can be easily measured, the method represents a con- venient way to gather structural type information at low cost.

10.2. Chemical properties

There are many tests commonly used to measure the chemical characteristics of a lubri eating base oil. Some of these are listed below: Ash Sulfated ash Carbon residue

Total acid number Sulfur

Nitrogen

Chlorine Water

Metals Composition analysis

ASTM D-482 ASTM D-874

ASTM D-189, D-524

ASTM D-664 ASTM D-129 ASTM D-3228

ASTM D-808, ASTM D-1744

D-974

D-1552, D-2622 D-1317

D-95 ASTM D-811, Atomic absorption spectrophotometry

ASTM D-2007, D-2549, D-3238

Ash content of an oil refers to the content of metals and other inorganics remaining

from an oil after combustion. Some metals like lead and magnesium can be lost during the combustion process due to the low boiling points of their oxides. Sulfuric acid can be added to convert the oxide to sulfates. This is then called sulfated ash. The carbon

residue basically reflects the asphaltene content in the base oil. The acid number indi- cates the amount cf acidic species in an oil which could be important in oxidation stability and corrosion. The sulfur and nitrogen contents of a lubricating base oil provides an approximate indication of the number of molecules containing sulfur and nitrogen atoms. Depending on their molecular weight and molecular structures, they could exert different

influences on oxidation stability and additive response. Chlorine and/or other halogens usually are not found in virgin base oils, but have been found in some re-refined oils.

Its effect on performance is not clear at this time. Metals such as iron, zinc, calcium, magnesium, and lead are important indicators in the case of re- refined oils. The metal

level reflects the completeness of the re-refining processes in removing residual additive

metals and wear metals in the used oil.

12. Results and Discussion

Various physical property and chemical property tests were conducted on a number of re-refined and virgin base oils. Seven re-refined base oils were purchased from various

re-refiners throughout the country in ten drum lots. After detailed characterization,

these oils could serve as reference materials for testing by various organizations and laboratories interested in examining re-refined oils. Some data were obtained from Amoco

Chemicals Corporation and some data from commercial labs. Differential scanning calorimetry [16,17] and the Ford free radical titration test [18] were run on these oils by other

technical divisions inside NBS. These physical and chemical data were initially collected

in an attempt to look at their correlation with base oil oxidation stability as defined by

the RBOT, DSC, and Ford titration tests.

In addition to the analyses on re-refined base oils, five virgin base oils of various

viscosity grades were also analyzed. The data on these virgin oils is shown in table 6. It would be noted that in some cases (e.g., the values of percent aromatic carbon between

the n-d-m method and low resolution mass spectrometry for the same oil) considerable varia

tions in test results exist. This supports our view that the test procedures and test pre

cision need to be firmly established experimentally before detailed characterization and correlation can proceed. For the virgin base oils, there also appears to be a wide range

in some of the characteristics; e.g., sulfur varies from 0.034 to 0.175 percent, and aromatics from 11 percent to 26 percent.

149
Table 7 shows the physical property data of the seven re-refined base oils. The indicated viscosities measured at 40 °C show that these oils represent a range of vis- cosity grades. The boiling point distribution data indicate that these oils have a relatively small amount of volatile light ends (percent off at 680 °F). Both the refractive index and the density data suggest that these oils are very similar and uniform in their major components.

The chemical properties of the re-refined oils are presented in table 8 and their hydrocarbon type analysis data are shown in table 9. Chemical property tests such as carbon residue, aniline point, carbon, hydrogen, and oxygen analysis all show substantial uniformity with a very narrow range among the seven re- refined base oils including oils manufactured by different processes and from different geographic areas of the country. Chemical composition analyses (i.e., hydrocarbon type analyses) also indicate the same

trend, e.g., aromatics range from 19.3 percent to 22.5 percent saturates range from 73.9 percent to 77.6 percent. Even the type of hydrogen distribution by nuclear magnetic resonance (NMR) analysis of four oils sugest remarkable similarities. However, variations

do exist in trace contaminant levels. This is demonstrated in the concentrations of chlorine (14 to 195 ppm), zinc (<0.2 to 37.9 ppm), and in the total acid number (0.076 to 0.81 mg K0H). However, these levels are generally relatively low, and the significance of the presence of these trace compounds in a lubricating base oil needs to be determined

with relation to oxidation stability. Oxidation stability tests were run on these seven re-refined base oils and the data

are shown in table 10. Three tests were conducted: the Rotary Bomb Oxidation Test (RB0T, ASTM D-2272), Ford free radical titration test, and Differential Scanning Calorimetry.

The RB0T measures the time it takes the oil to absorb/react with 25 psia of oxygen in the presence of copper and water at 150 °C. Usually the test is run with an additive or an additive package and it measures the oxidation and hydrolytic stability of turbine oils. The Ford Free radical titration test measures the ability of an oil to neutralize free radicals artificially released by a chemical at 60 °C. The results are expressed in molar concentration of anti-oxidant capacity. The test result reflects the amount of total anti-oxidant contributed both by additive and by naturally occurring molecules in the oil. The Differential Scanning Calorimetry test measures the oxidation onset temperatures of a small droplet of oil sample in a calorimeter under a high flow rate oxygen atmosphere.

The RB0T result suggests that there are considerable variations in oxidation stability

among the oils, from 27 min to 71 min. However, it is generally recognized that RB0T test which are run without additive or additive package is less precise and reflects the initial oxidation rate under solid metal catalysis. It is also difficult to distinguish between oxidation stability and hydrolytic stability in this test. The free radical titration test

data suggests the most stable oil to be RB007 and the least stable oil to be RB0059. In the DSC procedure, the trend of the data agree with the RB0T results. In our preliminary

attempts to correlate the physical and chemical property data with these oxidation tests, there appears to be some correlation between the free radical titration data and the sulfur content of the oil. However, more data will be required to confirm this observation.

13. Summary

The requirements of a lubricating base oil are varied, and the ability to characterize

base oils through their physical and chemical properties is felt to be important (along with appropriate engine testing) both in the acceptance of re-refined oils, as well as in evaluating virgin oils. In this paper, seven re-refined base oils have been characterized

in detail and do not appear to be significantly different from virgin base oils. Further,

the re-refined oils appear to be remarkably uniform in composition and characteristics. Trace contaminant levels are generally low but appear to reflect significant variations

among the seven oils. Three bench oxidation tests were applied to these re-refined oils, and the resul.ts suggest relatively small variations in stability. Contaminants which

appear to be potentially important include chlorine and polar components. Information of

the molecular structure of sulfur, nitrogen and oxygen compounds would be helpful in any correlation studies. More study will be required to confirm and expand these initial observations. Further, any test procedure utilized for such data gathering and correlation

studies must be evaluated experimentally with regard to its accuracy and precision.

150

UD

152
153

References

[1] Van Nes, K. and Van Westen, H. A. , Aspects of the Constitution of Mineral Oils , Elsevier Publishing Co., Amsterdam (1951).

[2] Bondi , A., Physical Chemistry of Lubricating Oils , Reinhold Publishing Corp., New

York, New York (1951).

[3] American Petroleum Institute Research Project 6 report, API, Washington, D.C. 20037.

[4] Denison Jr., G. H. , Oxidation of lubricating oils. Effect of natural sulfur compounds

and of peroxides, I.&E.C, 36, 5, 477 (1944).

[5] Denison Jr., G. H. and Condit, P. C. , Oxidation of lubricating oils. Mechanism of sulfur inhibition, I.&E.C, 37, 11, 1102 (1945).

[6] Vesely, V., Resistance of lubricating oils to oxidation, Fachber Qberf 1 aechentech , 12, 43 (1974).

[7] Von Fuchs, G. H. and Diamond, H. , Oxidation characteristics of lubricating oils. Relationship between stability and chemical composition, I.&E.C, 34, 927 (1942).

[8] Asseff, P. A., Current crankcase lubricants, Lubrication Engineering , 107 (March,

1967).

[9] Watson, R. W. , Petroleum additives - the role of alkyl groups, Proceedings of Joint ASLE/JSLE Lubrication Conference , Tokyo, Japan (1975). [10] Vesely, V., Relationship between the composition of lubricating oils and their oxidation stability, Ropa a Uhlie , 11, 297 (1969).

[11] Korcek, S. and Jensen, R. K. , Relation between base oil composition and oxidation stability at increased temperatures, ASLE Trans., 19, 83 (1976).

[12] Burn, A. J. and Greig, G. , Optimum aromaticity in lubricating oil oxidation, J. Inst, of Petroleum, 58, 346 (1972).

[13] Hsu, S. M. , Review of laboratory bench tests in assessing the performance of automotive crankcase oils, to be published in Lubrication Engineering . [14] Hsu, S. M. , Anti-wear and lubricity additives for lubricants, NBS SP. 487, Natl. Bur. Stand., Washington, D.C. 20234, 1977. [15] Wing, R. D. and Saunders, 0., Oil film temperature and thickness measurements on the piston rings of a diesel engine, Proc. Inst. Mech. Engr. , 186 , 1 (1972).

[16] Cranton, G. E. , Composition and oxidation of petroleum fractions, Thermochimica

Acta, 14, 201 (1976).

[17] Tsang, W. and Walker, J., Application of differential scanning calorimetry to the characterization of lub oils, Proceedings on Measurements and Standards for Recycled

Oil /Systems Performance and Durability, NBS SP 584, U.S. Department of Commerce, Washington, D.C. , 1980. [18] Mahoney, L. R. , Korcek, S. , Hoffman, S. , and Willermet, P., The determination of the anti-oxidant capacity of new and used lubricants; method and applications, I.&E.C

Product R & D, 17, 250 (1978).

155

Session 4 OIL ANALYSIS FOR ENGINE CONDITION MONITORING

157

National Bureau of Standards Special Publication 584. Proceedings of Joint Conference

on Measurements and Standards for Recycled Oil/Systems Performance and Durability held at NBS, Gaithersburg, MD, October 23-26, 1979. (Issued Nov. 1980)

WEAR PARTICLE EQUILIBRIUM MEASUREMENTS AND THEIR SIGNIFICANCE

R. D. Driver and E. R. Bowen Foxboro Analytical Burlington Center

78 Blanchard Road

P. 0. Box 435 Burlington, MA 01803 Ferrography is a technique for isolating wear particle debris from lubricating and hydraulic oils, the presence of which carry with them a history of the wear processes in the machine [1.2] 1

. Thus, the technique has fundamental applications in machine condition monitoring and failure prevention. The wear particles are significant in the metal types that

are present in the particle distribution as an indication of the wearing machine components

and in the particle size distribution and morphology which indicates the severity of wear in the system. In this paper, we shall discuss the fundamental principles which describe the working of the ferrograph, concentrating on the working of the on-line ferrograph. We shall also discuss the significance of equilibrium particle concentration in the oil system and its measurement using the ferrograph [3]. There are ferrographic instruments which provide both quantitative and qualitative

information. The analytical ferrograph is a laboratory instrument which is used when a permanent record, a ferrogram, of the precipitated particles is desired [4]. Metallurgical

and microscopy techniques may be used on the ferrogram to obtain a wealth of information on the wear state within a machine [5,6]. With this instrument, the techniques of magnetic

precipitation have been extended to the precipitation of paramagnetic particles. Further, with the development of magnetic fluids, many nonmagnetic particles have been precipitated

using the ferrographic technique. This has had important applications in the precipitation

and separation of biological particles [7]. A second type of ferrograph in use is the direct

reading ferrograph [8]. This is a self-contained unit with an optical measurement of particle

density for large and small particles; large particles being those approximately 5 urn or greater, and small particles being approximately 2 urn or less. The direct reading ferrograph is used as an early warning device to indicate that a more detailed investigation should be made with the analytical ferrograph. Another quantitative

instrument is the on-line ferrograph. It is similar in its magnetic design to the analytical

and direct reading ferrograph, but is an instrument which monitors particle wear in a purely

on-line mode. This is the instrument that has been used to study particle equilibrium as described in this paper.

A photograph of the on-line ferrograph is shown in figure 1. The machine-mounted sensor

on the left contains the magnetic precipitation device and wear debris sensors. The wear

debris at two different locations within the magnetic field is measured with capacitance

sensors. The wear analyzer shown on the right of the photograph contains the electronics

package and display which can be located up to 75 feet from the sensor. The instrument is a cyclical device which operates automatically. The time required to make the measurement

varies from 30 s to 30 min, depending on the concentration of debris in the fluid. At the

end of each cycle, particles are cleaned from the substrate by flushing. The instrument is a linear device, since it is the fluid volume required for a set amount of wear debris to be precipitated which is measured, thus effectively removing any nonlinear response characteristics of the magnetic precipitation technique. Two measurements related to the wear mode in the system are available to the operator; the total amount of wear debris in the system per

unit volume in ppm, and the percentage of large particles.

Figures in brackets indicate the literature references at the end of this paper.

159
A schematic diagram showing the magnetic precipitation cell is presented in figure 2. Oil containing the suspended magnetic particles is constrained to move along the substrate

surface. The magnetic field configuration produces a force on the particles towards the substrate, with the result that large particles are precipitated near the entrance while the smaller particles are precipitated further down the substrate.

To discuss the physical principles underlying ferrography in more detail, it is instruc- tive to consider the trajectory of a particle in the fluid as is shown schematically in figure 3.

Figure 2. Schematic diagram of the magnetic precipitation cell. 160
y

DISTANCE DOWN PERRCXsRANV

Figure 3. Schematic diagram of the fluid flow above the substrate showing the trajectory of a typical particle. The point of precipitation of the particle on the substrate will depend on the point of entry of the particles in the fluid stream and the equations of motion which

connect the velocity components. The motion of the particles in the z direction is the

local velocity of the fluid at a height y. On the assumption that the fluid flow rate

is an inverse function of viscosity q, we may write, £ (y.n> OJ

where g(y) is a geometric factor independent on the physical configuration of the fluid flow, but independent of the viscosity.

In the y direction, the motion of the particle is determined by the Stokes velocity caused

by the movement of the particle in the liquid under the influence of the magnetic force.

6 n n

jj| = I

n a

3 M H | (2) where p is the magnetic permeability of a spherical particle of radius a and the force on the particle is the standard result for a ferromagnetic particle in a high field gradient.

A differential equation for the particle connecting the y and z motion, independent

of time, may be obtained.

g(y) £ - 4 * h | (3) The exact solution of this equation requires a knowledge of the y dependence of g(y) and

the magnetic force. An extremely important property may be seen without solving the equation

explicitly; namely, that the motion of the particle in the fluid is independent of viscosity.

In the case of the on-line ferrograph, we may obtain a relationship connecting the fur- thest distance down the substrate that a particle of radius a will travel, namely,

Y

L3

Z

L (a) oc (4) where V

L is the thickness of the liquid layer, and the relationship does not depend on fluid

viscosity.

161
Another property of the ferrograph which may be deduced from the equations is that as long as the particles are randomly distributed in the fluid, and if the magnetic force on the particles is independent of the height of the particles in the fluid, the density of precipitated particles of a given radius on the substrate will be absolutely constant up to the cutoff (a). The consequence of this is shown in figure 4 for two particle sets, one

set being twice the radius of the other.

DISTANCE ALOMG FERROG.RANA Figure 4. Idealized diagram showing the density of precipitated particles on the substrate for two different particle radii. Now we wish to discuss the importance of the particle debris measurement and its correct interpretation in the diagnoses of the wear mode of a machine [3]. In any oil system, we may consider there to be an active element which is generating particles at some rate, a particles/cm3 /s for a particle radius a. The particle generation process will be one of the many wear modes that can occur in a machine. The machine will normally have a sump, an oil circulation pump, and a filter. Assume that the loss mechanism of the particles removes a fraction p of the particle per second. A simple equation may be written connecting the rate

of change of the number of particles in either of the constants a, p. Ma = a- P n(.t) (5) The loss mechanisms of the particles are generally due to filtration, settling, magnetic

separation, impaction on inertial separation, and chemical dissolution in the oil. These processes can all be described by the above equation. A further mechanism may be due to the breaking up of particles of some other radius b which would require an additional term of the form y djjt^ * However, this is not deemed to be a significant loss mechanism and is ignored. Assuming for the moment no time dependence to the constants a and p we obtain a general solution for the equation of

n(t) = |

(1 - e" pt

) (6)

It is very important to note that the constants a and p are strong functions of particle

size, particularly in the influence of filters on the constant p. Equation (6) describes the return to an equilibrium of the particle count after a change

of oil in the system. The time constant to come to an equilibrium is determined exclusively

by the constant p with 1/p being the 1/e time of the system. After a sufficiently long time

has elapsed, the equilibrium value of the ratio a/p will be reached for the particle count. Thus, the equilibrium particle count is directly proportional to the rate of particle production a with any change in a being measurable only after a time constant of the order of

1/p. Some curves demonstrating this dependence are given in figure 5. 162
Figure 5. The tendency to equilibrium of the particle count for different values

of the constants p and a/p.

It is an empirical fact that, for the most deleterious wear modes, the rate of production

of large particles increases at a faster rate than for small particles as engine wear increases.

Thus, the percentage of large particle readings on the on-line ferrograph is an important

number in the interpretation of condition monitoring. Further, since the time constant for

loss of particles is less for the large particles, they are a faster and more sensitive

indication of a change in wear. We have operated the on-line ferrograph on a test rig to monitor its ability to follow

particle history in a system and test some of our basic assumptions of the particle equilibrium

model. We built a test rig consisting of a 20 litre volume with a circulation pump operating

at a flow rate of 20 1/min. The rig has minimal dead space and no filter. Due to its con- figuration, the rig has a negligible rate of generation of particles, and the rate of loss

of particles, mainly due to particle settling, will be long. Test particles are introduced

into the system and their history followed with the on-line ferrograph. The rate of loss of particles of a given size should be given simply by the equation

n = n Q e" pt

(7)

A plot of the decay of the total particle count in the system on a log-linear scale is shown in figure 6. The slope of the line gives an average decay constant p. In figure 7, we plot some data for the decrease in density of large and small particles, with time demonstrating the quite different rates of decrease on the particles. There is a slight nonlinear

behavior to the data in all of these graphs, demonstrating some deviation to the dependence

predicted by eq. (7). This equation is valid for a single particle size range. The experimental data, however, is the average over a finite particle size distribution. Such a weighted average of decaying exponentials with different decay constants p will give a dependence as shown by the experimental data. The pursuit of this dependence is beyond the

scope of this paper and before more sophisticated data handling techniques are attempted, much

more experimental data must be taken.

163
164
References

[1] Anderson, D. P., Ferrographic analysis for hydraulic fluids, topics on contamination in hydraulic systems, SP-447 (Society of Automotive Engineers, October, 1979).

[2] Bowen, E. R. , Scott, D. , Seifert, W. W. , and Westcott, V. C. , Ferrography, Tribology

International, 9, 109 (1976).

[3] Anderson, D. P. and Driver, R. D. , Equilibrium particle concentration in engine oil, Wear, 56, 415 (1979).

[4] Hofman, M. V. and Johnson, J. H. , The development of ferrography as a laboratory wear measurement method for the study of engine operating conditions on diesel engine wear,

Wear, 44, 183 (1977).

[5] Scott, D. , Seifert, W. W. , and Westcott, V. C. , The particles of wear, Scientific

American, 88 (May, 1974).

[6] Barwell, F. T. , Bowen, E. R. , Bowen, J. P., and Westcott, V. C. , The use of temper colors

in ferrography, Wear, 44, 163 (1977).

[7] Means, D. C. , Hanley, E. N. , Rutkowski , R. , and Westcott, V. C. , Ferrographic analysis of wear particles in arthroplastic joints, Journal of Biomedical Materials Research, 12, 867

(1978).

[8] Anderson, D. P. and Silva, R. S. , The direct reading ferrograph - design, calibration, and

a field application, Lubrication Engineering, 35, [4], 203 (1979).

165
i
National Bureau of Standards Special Publication 584. Proceedings of Joint Conference

on Measurements and Standards for Recycled Oil /Systems Performance and Durability held at NBS, Gaithersburg, MD, October 23-26, 1979. (Issued Nov. 1980)

USED OIL ANALYSIS: PAST, PRESENT AND FUTURE

Charles F. Schwarz

1025 Cromwell Bridge Road

Martel Laboratories, Inc. Baltimore, MD 21204

1. Introduction

Engine oil analysis as a tool to monitor internal combustion engine conditions had its modest beginning over fifty years ago, and has since grown to be used worldwide. It is now recognized as a cost saving and effective method of preventive maintenance.

Commercial utilization of used oil analysis commenced in 1927 when a series of oil tests

was offered to fleet operators. Engine oils of this era were basically a cut from a barrel of crude with little or no additive treatment so that oil drains were recommended every 500 to 1000 miles. Many people believed the principal purpose of oil analysis was to determine the condition of the crankcase oil and when it should be changed, and they used the service for

this purpose. However, in the days of low-cost oil, many fleet maintenance men simply felt that it was about as cheap, or cheaper, to drain oil frequently as to pay for oil analysis. This

was most likely true up to the early 1950' s when oil technology permitted longer engine oil drain recommendations by engine manufacturers.

"Oil analysis" as it is known today is a generalized term referring to an analytical

process initiated by the Denver and Rio Grand Railroad in the late 1940 's and adopted by

the U.S. Navy in the 1950' s. The main reason for the development of the analytical process

was similar for both the railroad and the military. After World War II most of the railroads started to use diesel power instead of steam

for the locomotives and while the cost per mile decreased drastically, the problem of wear

and engine oil life reared its ugly head. Operating over the Rockies, the D&RG started to lose engines through excessive wear and catastrophic failures. Their test department looked around for an answer and over a period of time established a procedure utilizing new spectrographs methods. During the same period of

time the U.S. Navy was losing a large number of carrier aircraft due to engine failures. They

looked into the work published by the D&RG railroad and initiated a pilot program in the early

1950' s at the Pensacola Naval Base.

In a short time a number of problems on reciprocating engines was detected by oil analysis,

but as can be expected in any new procedures, many falsely indicated failures were also predicted. The number of engine failures detected, and the resultant reduction in plane ditching,

led the military to initiate a Joint Tri -Service program that has now been adopted by all three services.

The military oil anlaysis program has recently been renamed J0AP for "Joint Oil Analysis

Program". It consists of the former Air Force, Army and Navy programs: SOAP, A0AP and NOAP, respectively. Each program varies slightly depending on the type of equipment and geographical

distribution. This was brought about by new developments in instrumentation that has resulted

in the establishment of two analytical methods for routine determinations of wear, and measurement of contaminant and additive metals. These are Atomic Emission Spectrography and Atomic

Absorption Spectrophotometry. Both systems are in wide use and are extremely accurate in most determinations provided that the limitations of each are recognized by the laboratories,

as both methods use similar principles in achieving their analysis.

167
Atomic absorption (AA) involves aspirating a diluted solution of the oil sample into a controlled air-acetylene or nitrous oxide-acetylene flame. A lamp containing a hollow cathode constructed of a specific element is used to produce a high-intensity beam of that element's emission spectrum. The beam is split in two; one half is used as a reference, and follows an uninterrupted path to a photomultipl ier detector. The other half passes through the flame be- fore reaching the detector. The detector system thereby measures any loss of intensity of the sample beam due to its passage through the flame. Atoms of the element present in the flame

will absorb light of that element's characteristic wavelengths, the absorbance being proportional to the concentration of the element in the oil. Oils containing precise amounts of the elements of interest are used as standards. Either absorbance or concentration can be read directly on modern instruments, or fed into a teleprinter or computer. Atomic Emission (AE) is similar to AA; however, it energizes a small oil sample with a sufficiently high voltage to cause the individual metal in the sample to emit a characteristic

spectrum of ultraviolet and visible light. For each element in the oil sample, the intensity

of a specific characteristic wavelength will be proportional to its concentration.

The previous description of each process is highly simplified, and each oil analysis laboratory has its own reason for selecting which method is best suited to its overall operation.

2. Basis of Spectrometric Oil Analysis Spectrometric oil analysis is based on the fact that movement of metallic parts in an oil-wetted system is always accompanied by friction. Consequently, some surface metal is removed, and the microscopic particles are picked up by and are circulated with the oil. Friction is the major cause of wear particle formation, but corrosion, abrasion, scuffing, scraping and spalling are also contributors; in addition, combustion by-products become trapped in the circulating system. Therefore, the circulating oil contains valuable in- formation concerning the system's condition.

Metal flakes or particles usually found in screens, filters or detectors are not the basis of spectrometric oil analysis. Particles of this size tend to settle out and not appear in the oil sample. Their presence is important, but detection must be left to other

techniques. As a general rule, the following detection techniques are used for different particle size in micrometers.

1) Visual Screen and Filter Evaluation: 45-2000 urn. 2) Chip Detectors: 10-600 urn. 3) Microscope Examination or Ferrography: 4-200 urn. 4) Spectrometric: 0-15 urn. To be a successful preventive maintenance tool, spectrometric oil analysis must indicate

the very first stages of wear, when colloidal material is being generated. Through periodic measurements of oil samples for metal composition, a normal wear trend can be established.

The metallic contents of the used oil can indicate wear, contamination and additive content.

3. Valid Sample for Valid Results

A good sample is vital for the success of any program. The results can be no more repre- sentative than the sample. For this reason the oil should be hot and well mixed when the sample is taken. New oil samples are important in order to characterize the oil itself. Samples should be taken at least every oil change in case of severe operating conditions or extended drain periods, and at least once between every drain. For very long drain periods,

i.e. 100 000 miles for over-the-road service suggested by one diesel engine builder, a sample should be taken every 20 000 to 25 000 miles. This paper will only cover wear metal analysis. Many laboratories offer a variety of programs depending upon the needs of the customers. No attempt will be made to list the many

and varied tests offered and it is often very difficult for a fleet superintendent to decide what program he needs.

168
Common sources of elements found by spectrometric oil analysis: SOURCE

Iron (Fe)

Silver (Ag) Aluminum (Al) Chromium (Cr) Copper (Cu)

Magnesium (Mg) Sodium (Na) Nickel (Ni) Lead (Pb) Silicon (Si) Tin (Sn) Titanium (Ti) Boron (B) Barium (Ba) Molybdenum (Mo) Zinc (Zn) Calcium (Ca) Phosphorus (P) Antimony (Sb) Manganese (Mn)

Most common wear metal. Cylinder walls, valve guides, rocker

arms, piston rings, ball and roller bearing, bearing races, spring gears, safety wire, lock washers, locking nuts, locking

pins, and bolts. Bearing cages (silver plating), puddle pumps, gear teeth, shafts, and bearings in some reciprocating engines. Spacers, shims, washers, pistons on reciprocating engines, cases on accessories, bearing cages in planetary gear, crank- cases in reciprocating engines, and some bearing surfaces. Plating metal, replacing silver in many newer engines. Seals, bearing cages, piston rings, and cylinder walls on reciprocating

engines, and coolant leaks due to chromate corrosion inhibitors. Present in the form of an alloy, either bronze or brass, therefore usually detected in conjunction with tin for bronze alloys,

and zinc for brass alloys. Main or rod bearing thrust bearings, wrist pin bushings, oil coolers, gears, valves, turbocharger

bushings, washers, and coolant leaking from copper radiators. Used to save weight in aircraft engines. Cases for accessories, component housings, and water in marine equipment. Also an oil additive. Coolant, grease, and seawater (in marine equipment). Bearing metal, valve train metal, and turbine blades. Bearing metal (generally confirming high copper or aluminum

caused by bearing wear) seals, solder, paints, and greases. Not applicable for engines using leaded gasolines. Found in most oil samples owing to airborne dust, seals, and,

in some oils, from an anti foaming additive. Bearing metal and bushing thrust metal, wrist and piston pins, pistons, rings, oils seals and solder.

In certain types of jet aircraft engines: bearing hubs, turbine blades, and compressor discs.

Seals, airborne dust, water, and coolant.

Oil additive, grease, and water leaks. Piston rings on some diesels, electric motors, and oil additive. Brass components, oil additive, neoprene seals, grease,

and coolant.

Oil additive, grease, and some bearings.

Oil additive and coolant leaks. Alloys in bearings, and in grease. Valves, blowers, and exhaust and intake systems. Spectrometric oil analysis is now recognized by all major equipment manufacturers, oil companies, commercial aircraft owners, railroads, marine equipment operators, and the military.

4. Military Equipment

Under contract to the Army, Martel is now operating the oil analysis laboratory at Hunter Army Airfield as an integral part of the Installation Maintenance Division, DIO, Headquarters 24th Infantry Division at Fort Stewart, Georgia. At this installation we utilize a Baird-Fluid Analysis Spectrometer, FAS-2A, approved by the military under MIL-S-83129A. This laboratory receives samples from all military installations within several hundred miles of Savannah, Georgia and includes both ground vehicle and aircraft samples. In addition to the standard wear metal analysis, this laboratory is equipped and manned to perform

many other tests on fuels and lubricants for the military.

169
5. Trucking Industry Vehicle manufacturers offer oil analysis. More than 50 million miles of Mack engine test data bolster the MaxiGard Early Warning Engine Analysis introduced in March, 1978, by Mack

Trucks, Inc., Allentown, PA. The MaxiGard service program is an outgrowth of many years of monitoring actual engine performance both in the laboratory and in fleet operation. The MaxiGard oil analysis includes both physical measurements and wear metal analysis using a Perkin-Elmer Model 603 atomic absorption spectrophometer. This method was chosen because of the precise readings and background data base information available at Mack Trucks. The program is believed to be unique in that it is the only oil analysis program in which

the engine manufacturer participates in the daily recommendations and interpretations of the results obtained in the laboratory.

A key part of the MaxiGard service is the truck enrollment form. When the first sample

is received for a truck being enrolled in the MaxiGard program, the form is used to record the truck owner's name, address, phone number, the emergency contact and the name of the Mack

Service Center that services the customer. This form also gives comprehensive vehicle information, including engine model and serial number, chassis model and number, transmission and rear axle model numbers, vehicle operating

location, type of truck use, mileage at time of enrollment and since last overhaul (if applicable). The oil brand name, change interval, SAE grade and the crankcase capacity are included, together with the type of coolant used. All of these items are important as they

are taken into account when making recommendations to the truck owner.

It is here that the value of the vast Mack experience file, and review of the suspicious

oil analysis come into play. Since the test evaluation engineers are familiar with the service condition and typical wear patterns for Mack vehicles in all types of application,

they can make a very prompt, accurate diagnosis of the oil analysis results that fits into the vehicle operating conditions. For example, an oil test result that would be "suspicious" in a line-haul tractor might be normal for a truck in a severe off-highway or construction

application.

6. Private Aircraft

The AiResearch Manufacturing Company of Arizona, a Division of the Garrett Corporation,

has recently designated several laboratories as approved facilities for an Oil analysis pro- cedure developed by them. This analysis has been specifically designed for their TPE 331 Turboprop, TSE Turboshaft and TFE 731 Turbofan engines. This procedure includes both spectro- metry analysis and filter content evaluation. The value of the spectrometric analysis has been discussed in detail and we will not dwell on the merits here except to emphasize the importance of establishing a "norm" for each engine and then looking for trends in future

analyses.

6.1. Filter content evaluation

Coarser or more rapid wear of internal engine parts results in production of larger metallic particles which are trapped in the engine oil filter. Observation under a stereo- scopic microscope of the size and shape of these particles, along with a chemical analysis to determine the elements or alloys present, can provide important information as to the source

of such materials. The sampling interval is taken into consideration when deciding whether

the total weight of accumulated metallic particles is normal or necessitates a resample request on inspection.

6.2. Evaluation of analysis results Aircraft Maintenance & Engineering and Flight operation personnel are kept abreast of the program through Service Information Letters (SIL) on a regular basis. Both oil samples and filters are forwarded to the laboratory for analysis and the following evaluations are generally reported.

1) The oil wear trend is normal.

170
2) Increases are such that a resample is recommended in order to monitor

the wear trend.

3) Increases are such that an engine inspection is recommended to find source of abnormal wear.

7. Commercial Airlines Spectrometric oil analysis in commercial airlines in used in an integral part of an engine maintenance program. In addition, engine performance monitors, non-destructive tests

and oil screen or filter inspections are utilized. Few engines are pulled off because of oil analysis results alone; additional monitors are generally consulted for verification.

The major pitfall in the use of oil analysis by commercial airlines or the military is basing maintenance on threshold limits of wear metals. Engine removals based on a pre-set

upper limit for one or several elements are frequently found to be unnecessary. A Pratt &

Whitney JT&D turbine, for example, may exhibit a trend of 4 ppm of iron, while another engine

of the same model may perform normally at 80 ppm. An increase in the first engine to 8 ppm would be cause for alarm since the iron concentration had doubled. The wear metal generating

trends of engines are never identical and threshholds are generally meaningless.

In summary, I would like to emphasize the importance of obtaining a "norm" for each engine

regardless of its type, make or model. Many people, especially those oriented towards simplifying

maintenance schedules, and many new people involved in oil analysis, keep asking for the ultimate,

that is, the final threshold limit for their vehicles. This is also why it is extremely difficult

for a technician to evaluate the results. Computerized programs are also being used, but without

the human evaluation the many pitfalls can place the program in jeopardy.

1) The price of lubricating oil will continue to increase and this, sampled with

larger sump capacity, will make longer oil drains more desirable. Oil analysis

can and will play an important part in reducing operating costs as additive packages

are designed to permit longer drain intervals.

2) Due to noise reduction mandated by DOT and others, the internal temperature of the engine may tend to run higher and friction and wear may become a more serious

problem. Again oil analysis may be helpful.

3) More on-board oil monitoring devices will be designed and built and may one day

be standard equipment on large vehicles.

4) There will be new advances in instrumentation to help identify specific alloys,

so that wear debris can be more readily identified, thereby pin-pointing more accurately the location of the wear.

5) Wear metal analysis will pay a very important role in developing the data necessary for evaluating the use of re-refined oils in fleet operation.

The author would like to thank Mr. James F. McCadden, Manager, Fluid Analysis Systems, Government System Division, Baird Corporation, and Mrs. Diane M. Lawrence, Atomic Spectroscopy

Products Department, Perkin-Elmer Corporation for their support in supplying information for

this paper and Dr. Robert Edwards, Director of Laboratory Services, Martel Laboratories, for

his contribution and review of the technical information.

8. A Brief Look into the Future

171

National Bureau of Standards Special Publication 584. Proceedings of Joint Conference

on Measurements and Standards for Recycled Oil /Systems Performance and Durability held at NBS, Gaithersburg, MD, October 23-26, 1979. (Issued Nov. 1980)

WEAR PARTICLE ANALYSIS FROM GREASE LUBRICATED BEARINGS William Rosenlieb

SKF Industries, Inc. 1100 First Avenue

King of Prussia, PA 19406

and Alan S. Maciejewski

U.S. Naval Air Engineering Center Tribology Laboratory, Code 92724

Lakehurst, NJ 08733

1. Introduction Previously no diagnostic method had been developed for evaluating or examining samples

of used grease to determine the wear state/condition of mechanical devices, in which the grease was used as the lubricant. Such mechanical devices would include gears, cams, splines, bearings, etc. The purpose of the study discussed here was to experimentally investigate

the feasibility of determining the life state of one mechanical device, ball bearings, by monitoring the grease retained wear debris. The ferrography method was used to evaluate the debris and the results compared with those obtained from the physical examination of the bearing. The development of the technique required to reduce the grease samples to a condition

where they could be examined by the ferrography method and the ferrography work was per- formed by the Naval Air Engineering Center (NAEC). The bearing testing, grease sampling,

and examination of the bearings was performed by SKF Industries, Inc. The program consisted of the testing of three pairs of grease lubricated bearings. The

first set was run continuously to a time up life of 230 x 10 g cycles or until a grease or bearing failure occurred before the grease samples were taken and the bearings examined. In contrast, grease samples were periodically taken for wear debris analysis throughout the testing of the second set of bearings and detailed inspection of the bearing performed fol- lowing test termination. During the testing of the third set of bearings, the grease samples were taken and the bearings were inspected periodically.

2. Test Equipment and Procedures

2. 1. Test machine

All testing was conducted using SKF developed R2-type Bearing Endurance Testers. Each machine is comprised of a symmetrical horizontal arbor supported on two cylindrical roller

bearings (load bearing) which in turn are supported in split main housings. Labyrinth seals

are located on both sides of the load bearings to minimize the escape of the recirculating

oil supplied to the bearing for lubrication and cooling. Two test bearings (type 6309 are press fit on the arbor, one at each end, and support a teardrop shaped housing through which

the radial load is applied by a deadweight lever arm system. The test bearings are encapsulated by two rings, which form a labyrinth seal on the inboard side of the bearing, and a face plate on the outboard side. Two metal shields are located, one on each side of the bearing, to further minimize the ingestion of external debris and retain the grease and bearing wear particles in the bearing.

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The test shaft is belt driven by a 15 HP constant speed AC motor through pulleys selected to provide the desired test speed. The load bearings are splash lubricated with oil supplied from a central recirculating system at a rate sufficient to control the bearings' operating temperatures. The recirculating oil system contains a 25 pm full flow filter. The test bearings outer ring operating temperatures are sensed by shielded thermo- couples and monitored by a minicomputer control system. The test bearing temperature mea- sured at each 12 min interval is stored in the computer and printed out each 8 hs to provide a hard copy log of the thermal history of each test bearing.

A vibraswitch, attached to the main housing, monitors the general vibration level of the machine and turns off the drive motor when a significant increase, typical of a bearing failure, occurs.

2.2. Testing and bearing preparation and inspection procedure

The following procedure was used in preparing and mounting the test bearings, taking

the grease samples, and inspecting the test bearings.

2.2.1. Initial marking and cleaning of bearings

All test bearings (type 6309 manufactured from carbon-vacuum-deoxidized [CVD] 52 100 steel) were disassembled and the rings numbered in sequence using an electric etching

pencil. The outer and inner rings, cages and shields of Set II bearings were divided in sixteen equal segments and marked with the electric etcher. Every other segment was numbered in order from 1 to 8. Each bearing was assembled and placed in a horizontal position in a glass container partially filled with solvent and ultrasonical ly cleaned for

5 mins. Each bearing was then removed and flushed with petroleum ether and allowed

to air dry. 2.2.2. Greasing of bearings

Each bearing was charged according to standard practice with approximately 12.6 grams

of grease to obtain a 1/3 full pack. The grease charge was inserted uniformly on both

sides of the bearing between the balls using a hypodermic syringe. The shields, cleaned

with solvent and petroleum ether, were placed on both sides of the bearing and the bearing wrapped in coated paper in preparation for assembly into the test rig. 2.2.3. Assembly of bearings in rig Prior to the assembly of the bearings onto the shaft, the shaft bearing seats and sur- rounding area were washed with naphtha and wiped dry with a lint free rag. The bearings were pressed onto the shaft using the specially adapted hydraulic ram which was also cleaned with

naphtha prior to use. The marked side of the bearing was located on the outboard side of the

shaft. The bearing housing, following cleaning with naphtha, was assembled with the bearing

type number on the outer ring located at the 12 o'clock position.

The desired radial load of 2600 lbs was applied to each bearing. This was accomplished

by calculating the necessary load to be applied to the load arm and checking the weights on

a spring scale before attaching. The runout between the end of the shaft and face of the bearing housing was checked and the necessary adjustments performed to assure proper align- ment before starting the test. 2.2.4. Testing

All testing was performed at an inner ring rotational speed of 5500 rpm wth a radial load of 2600 lbs applied through the bearing housing. The bearing temperature recording computer was programmed to incorporate a subroutine (Temperature Rate of Increase Monitor) which would automatically stop the drive motor when a temperature increase rate of 1.1 °C per minute or greater for a period resulting in an 11.7 °C cumulative increase occurred,

or when an operation temperature greater than 120 °C was sensed.

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Bearing Set I was run in an uninterrupted manner. Testing was sustained until one of the following occurred: 1) a failure of both bearings was experienced, as indicated by an increase in bearing vibration level and/or audible noise, 2) a grease pack failure was ex- perience, as defined by the Temperature Rate of Increase Monitor, or 3) a bearing life of 230 x 106 inner ring revolutions, roughly equivalent to the theoretical L 5 o, was achieved without failure. If testing was automatically stopped due to an excessive temperature in- crease rate or high temperature, the test was restarted and continued until stoppages oc- curred within 10 hs or less of each other. At the conclusion of the test, the bearings were carefully removed from the rig using

a special puller which was cleaned with naphtha just prior to use. The major portion of the grease was then removed from the four areas (inner ring, outer ring, cage and shields) using

a small stainless steel spatula and placed in separate compartments of a clean glass container. Each bearing was then placed in a glass container with solvent and ultrasonical ly cleaned. Following the cleaning, the cleaning fluid and debris was placed in a glass bot- tle and sealed with a plastic cap using a teflon sealing disk. The grease and cleaning

fluid were refrigerated until delivered to NAEC for analysis. The bearings were disassembled and a visual inspection of all elements performed using

an optical microscope with magnification up to 30X. The inner ring surfaces were also ex- amined with a scanning electron microscope to further determine the degree of surface damage

and necessary photomicrographs were taken for documentation purposes. Bearing Set II was tested in the same manner as Set I except grease samples were re- moved after 1, 5, 10, 20, 52, 80, 120, and 160 million revolutions. The grease samples were

removed from the outboard side using a small stainless steel spatula from a numbered seg- ment on the cage, inner ring, outer ring and shield starting with segment number 1 and progressing through number 8 after each progressive operating period. The removed grease

was replaced by approximately the same quantity prior to restarting the bearing. Following the test termination, the same procedure was followed in removing the grease and ex- amining the bearing as in Set I. Bearing Set III was tested in the same manner as Set II except at each shutdown interval the bearings were removed and the grease sampling, bearing cleaning and examination

performed in the same manner as that performed at the termination of Set I testing.

3. Test Discussion and Results

3.1. General discussion

r An applied radial load (P) of 2600 lbs (k = 3.5) was selected for use during the

testing. This load results in a theoretical Ljq life of 43 million revolutions for the 6309 test bearing which has a basic load rating (C) of 9120 lbs. The theoretical L 5 o life of the test bearings were calculated to be 230 million revolutions which was also selected to be the time up life of the test to insure the fatigue failure of several

bearings.

An inner ring rotational speed or shaft speed of 5500 rpm was selected to limit the operating test period of a given test bearing to 708 hs. Consideration in selecting the speed was also given to the expected outer ring operating temperature rise which would

occur. Experience obtained in prior tests using the same load indicated that the expected

temperature rise would be between 77 °C and 90 °C. This was considered to be reasonable and would not impose excessive restrictions on the selection of the grease.

The selection of the grease was based on properties which were compatible with both

the test conditions and the analysis techniques used by the NAEC to separate the debris

from the grease. The grease selected meets MIL-G-23827 specifications and consists of a lithium soap base and a di -ester lubricating fluid. The specified temperature range of

the grease is -73 °C to +120 °C. Greases meeting this military specification are reportedly

one of the three most frequently used greases in naval aircraft applications and is therefore representative of what would be found in practice.

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Samples of the grease, in unopened one pound cans as received from the vendor, were sent

to the NAEC. The samples were inspected and found to contain small metal particles. Therefore, grease samples removed from the bearing for NAEC examination would be expected to con- tain such particles in addition to metal debris generated in the operation of the bearing. The two basic methods used to detect the initiation of a bearing failure during the testing portion of this program were vibration level monitoring and temperature rate of increase monitoring (TRIM). The vibration monitoring is a standard procedure used in bearing endurance testing and is utilized to turn off the drive motor when the vibration

level increases to a value representative of that produced by a small spall in one of the bearing elements. The TRIM procedure (developed by SKF to detect early warnings of lubri- cation failures in grease lubricated bearings) turns off the drive motor when a bearing temperature increase rate is such that a recovery of the bearing grease system would not

be expected and, thus, a catastrophic bearing failure would result if the bearing were allowed to continue running for an additional short period of time. During the test program, grease samples were taken from four different locations (inner ring, outer ring, cage, and shield) each time samples were extracted. The grease removed from each location was stored in separate compartments of a glass petri dish to permit the determination of the most sensitive location with respect to the generated

debris. The quantity of grease removed from each location was also representative of the amount of grease present and thus could be used to determine if adequate sample sizes would be present at the various locations in actual applications.

It was observed during the grease sampling that fretting material generated between the bearing housing and outer ring sometimes dropped into the grease on the bearing shields during

the removal of the bearing from the shaft or during grease sample removal. Attempts were made

to remove this material from all samples supplied to NAEC to eliminate confusion during evaluation. However, since there was no assurance that all fretting material was removed, a sample

of the material was supplied to NAEC for examination and categorizing, thus permitting its iden tification if found in the grease samples. Although the presence of the fretting material was undesirable, it is also quite likely that it would be present in more applications and special care would have to be taken to minimize its presence in grease samples. Of the six bearings tested, three experienced failures which terminated their testing

before time up and a fourth experienced several TRIM shutoffs before reaching time up. Of the three failures, two were the results of inner ring spalls and the third due to TRIM shutoffs which occurred within three hours of each other.

3.2. Testing results

3.2.1. Set I bearings (nos. 01 and 02) After 158 hours of testing, a TRIM shutoff occurred due to a fast rise in the temperature

of bearing 02. After four additional TRIM shutoffs, with only three hours of operation be- tween the last two, and one high temperature shutoff, the testing of bearing 02 was termi- nated after 302 hs or 98 x 106 revolutions.

The inspection of the bearing showed that advanced surface distress had occurred in both races with five bands readily detectable in the ball tracks. The two Heathcote bands were dark gray in color with only a few fine finish grinding marks still present. The center microslip band was highly glazed with some microspalling which was also present in the other two slip bands. The balls had a mottled appearance with several discoloration

bands present. In general, the discoloration and high degree of surface distress indi- cates that inadequate lubrication had existed at some time during its operation. This finding agrees well with the testing history of several trim shutoffs. Although the damage to this bearing was not sufficient to prevent further operation if it were regreased, the period of further operation before a surface initiated spall is likely to occur is considered to be greatly reduced when compared to an undamaged bearing. Should the bearing be continued in use without regreasing a thermal imbalance failure is likely to occur within the next few hours of operation. Thus a bearing in this condition

should be replaced.

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Testing of bearing 01 was continued using a dummy bearing in place of 02. After an additional operation of 5 x 106 revolutions or a total of 103 x 10 6 revolutions a TRIM

shutoff occurred. After attempting to restart the test, a vibraswitch shutoff occurred

indicating a spal 1

.

The inspection of bearing 01 showed that appreciable surface distress had occurred as evidenced by the highly glazed and frosted appearance of the ball tracks which were similar

to those in bearing 02. In addition a small spall had occurred in the inner ring. The sur- face damage and the initiation of the spall that occurred in this bearing would dictate its replacement as further running would quickly result in an inoperative bearing.

3.2.2. Set II bearings (nos. 03 and 04) The testing of Set II bearings proceeded without incident with grease samples removed

as scheduled after 1, 5, 10, 20, 52, 80, 120, and 160 million revolutions. During the testing period from 160 million revolutions until test time up of 231 million revolutions, four TRIM shutoffs occurred due to excessive temperature increase rates in bearing 04 with no shutoffs occurring due to problems in bearing 03. Inspection of bearing 03 following test termination at time up showed all elements to

be in excellent condition. The ball tracks in both the inner and outer races were only evident due to minor plastic flow of asperities which caused the contacted surfaces to have a slightly higher polished appearance than the uncontacted surfaces. Finish grinding lines were still present over the complete ball track further indicating minor surface

wear. The inspection of bearing 04 showed that appreciable surface distress had occurred in the races with microspalls and microcracks present in both. The ball track was evident

over the full circumference of the outer ring indicating that the radial clearance had been

lost for some period during the test. This condition and the surface distress both indi- cated that inadequate lubrication existed at some time during the test.

In general the inspection of these two bearings indicates that bearing 04 was very

close to failure and should be replaced. Whereas, there was no physical evidence in bearing

03 that would suggest appreciable wear or that the bearing should be replaced due to an im- minent failure.

3.2.3. Set III bearings (nos. 05 and 06) The testing of Set III bearings proceeded without incident with the grease samples

taken and the bearings inspected as scheduled through 20 x 10 6 revolutions. At 52 x 10 6 revolutions, a vibraswitch shutoff due to a spall failure on the inner race of bearing 06 occurred. The inspection of the inner ring of bearing 06 after 20 x 106 revolutions showed the

race to be in excellent condition. The presence of finish grinding lines across the com- plete race indicated that little wear had taken place and no surface distress had occurred.

The inspection after 52 x 10 6 revolutions showed the race to be essentially in the same ex- cellent condition except for the presence of the small spall and the appreciable denting

produced by spall debris. In general, no physical evidence had been noted during any of

the prior inspections which would indicate that the bearing was close to failure. The failure is considered to be a classical fatigue spall. The testing of bearing 05 continued per schedule to a time up of 230 x 10 6 revolutions

without any unscheduled shutdowns. The inspections of this bearing showed only small or subtle changes in the wear state through 160 x 106 revolutions. The inspection after

230 x 106 revolutions showed that appreciable micropitting had occurred indicating that the quality of the lubrication had worsened at some point during the final run. Although the surface distress of this bearing was not nearly as bad as that in bearings 01 and 02, its replacement would be recommended.

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4. Wear Particle Analysis

4.1. General discussion

Prior to conducting sample analysis of the used grease samples, an effective method to dissolve the grease matrix needed to be developed. The ferrographic technique utilized, re- quired that the grease be dissolved so as to result in a fluid type mixture capable of being passed through a narrow tube by means of a parastaltic pump onto a glass substrate. In ad- dition to assuring a fluid-type composition, the resulting mixture would produce an acceptable ferrogram to analyze the resulting wear particulate. This would serve as aid in trending from sample to sample the wear state condition of the component.

4.2. Solvent evaluation

In order to dissolve the grease, a study was undertaken to evaluate various solvent

combinations. Due to the various additives used in the composition of greases, a single, universal solvent could not be found. Various greases were tested, using varying amounts

of grease and combinations of solvents, based upon solubility and residue of the resulting

mixture. From these tests, three grease solvents were chosen based upon their wide-spread

application. Solvent #1 was composed of 50 percent toluol and 50 percent isopropanol. This solvent was found to be ineffective with lithium soap greases. Solvent C was composed of

33 percent toluol, 33 percent methyl ethyl ketone and 34 percent isopropanol. This solvent

showed a somewhat similar effect as solvent #1 on lithium soap grease. Solvent #3, composed

of 30 percent toluol and 70 percent hexane, appeared to be the most universal solvent, as

its solvating action is applicable over a wide selection of greases, including lithium soap

grease.

4.3. Used grease analysis During testing of the various solvents, it was noted that the grease being solvated was

in an unused state as opposed to a "worked condition". Additionally, the unused grease sam- ples were found to contain various metallic and nonmetallic particulate.

The metallic and nonmetallic particulate, contained in the unused grease, appears to

be from the processing and packaging of the grease. Numerous ferrogram studies were con- ducted, in order to characterize this particulate. In addition, SEM and XDS analyses were conducted to determine shape and elemental composition. This work resulted in data which

enabled the evaluator to eliminate those particulate from the grease that were observed with those from the actual wearing component.

In order to determine the difference in solvating unused and worked grease, numerous grease samples obtained from aircraft components and subjected to the various solvents

stated previously. As a result of these studies, solvent #2 was found to be more effective with worked grease. The principal reason was the ferrograms were virtually free of residual grease material as opposed to that observed using solvent #3. Therefore, solvent

#2 was chosen for the preceding analysis.

4.4. Sample preparation procedure

The procedure for preparation of the grease samples for ferrographic analysis was ac- complished in the following manner: 1) Ten 3 mm diameter glass beads were placed in a 1/2 oz bottle. The use of these glass beads aided the agitation process of the grease

solution. Their presence had no noticeable effect on the resulting ferrograms. 2) Varying amounts of used grease range in size by weight of between .01 to .035 gm, were then added to the bottle. The amount used corresponded to the time of the sample extraction

and the operating parameters of the specific test. 3) Five cc of solvent #2 were poured

into the bottle. The sample bottle was then closed and hand-shaken vigorously until such

time that the grease became dispersed. 4) Five cc of filtered MIL-C-23699, a synthetic polyester fluid, was then added to the grease mixture. This fluid was added to increase

the viscosity index of the grease mixture to aid in the delivery of the mixture to the ferrogram substrate. Additionally, the grease used (MIL-G-23827) has a di-ester lubricant

additive, which makes it compatible with MIL-C-23699. 5) Sample was then recapped and

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shaken vigorously. Five cc of the grease mixture/polyester solution was then removed by pipet into another 1/2 oz bottle. A ferrogram was then prepared from this mixture using filtered solvent #2 as a washing/fixing solution. The resulting grease samples from the bearing test were obtained from four different

locations (inner ring, outer ring, cage and shield) each time samples were extracted. The quantity of grease removed was representative of the actual amount of grease present at the time of sampling. This served as an indicator as to what areas of the bearing furnished

adequate amounts of grease for actual field sampling. These various sampling locations were studied to determine the sensitivity to the actual wear of the bearing surfaces by wear particle retention.

5. Wear Particle Analysis Results

5.1. General discussion

The first bearing analyzed was bearing #1 of the endurance test. Due to the nature of the test, only one sample was taken, at the time of failure. Ferrograms were made of the resulting samples to determine the best location for sampling in terms of amount of grease available and sensitivity to wear. Based upon the results of these ferrograms, the cage and ball sampling location seemed

to reflect the actual wear state of the bearing as well as provide an adequate amount of grease for testing. The inner ring had an insignificant amount of grease, therefore it was

not tested. The outer ring provided an adequate amount of grease for analysis, yet the size distribution and total number of particles were considerably less than the cage and

ball sample. The shield contained an adequate amount of grease, but the size distribution

and total number of particles was considerably greater than either the cage and ball and outer ring areas. Of significant note was the abnormally high percentage of large ferrous metallic particles found in the shield sample. This may suggest the need to take a closer- examination of the trend in particle migration outward from the interior of the bearing. The bearing had shut down due to a lubrication failure and a spall which had developed

on the inner ring. The size distribution of particles and particle types observed indicated

substantial wear had taken place and an abnormal wear mode was taking place. The grease had a very dark brown/black appearance. This was an indication that the grease had degraded, as evidenced by the TRIM shutoff of the test. Optical and SEM inspection by SKF personnel revealed appreciable surface distress had occurred in the form of micropitting, denting and plastic deformation. Replacement of bearing would be recommended.

Of the remaining five bearings, three are selected for discussion here. These bearings represent both Set II and Set III and are representative of a bearing reaching the termination point without distress, a bearing reaching termination point with some distress and a bearing experiencing failure.

5.2. Set II bearings (no. 03) Bearing #3 of Set II ran to the predetermined termination point of 230 MIL REVS. Based upon the observation made of Set I, the cage and ball sample will only be discussed.

5.2.1. Wear in Wear in occurred between 1-5 million revolutions. The ratio of large to small particles

was indicative of a normal wear in process. The quantity of particles was high, which is normal. Wear in particles (long, flat, narrow strips) normally associated with wear in of new surfaces were observed. The other wear particles observed revealed no other abnormalities.

5.2.2. Normal wear

Transition to normal wear occurred at the 10 MIL REV sampling point and continued to the 160 MIL REV point. The number of break-in type particles had diminished. The generation rate of normal rubbing wear particulate increased up to the 20 MIL REV point. From

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that point, laminar wear particles increased in number as the rubbing wear particles de- creased. No other signs of abnormalities were observed. The size distribution and other particle types showed no signs of abnormality.

5.2.3. Wear out After 160 MIL REV point, a somewhat accelerated wear rate had occurred. At the termi- nation point in testing (231 MIL REV) this accelerated wear condition did not worsen sig- nificantly to any great extent. Of particular note was the increase in severe wear particles, though not in any great quantities to warrant immediate concern.

5.2.4. Optical and SEM examination

Optical and SEM examination by SKF personnel revealed that minimal wear and plastic flow had occurred and that the bearing was well lubricated throughout the test. The bearing wear state/condition was suitable for continued operation.

5.3. Set III bearings (no. 05) Bearing #5 of Set III ran to the predetermined termination point of 230 MIL REV with

some surface distress.

5.3.1. Wear in Wear in occurred between 1 and 10 MIL REV, as opposed to 1 to 5 MIL REV in bearing #3. The longer wear in process may be attributed for the most part to the nature of the test (dismantle/inspect/regrease) which produced a significant lower number of wear particulate

due to the lack of accumulation of wear particulate in the grease. Additionally, wear in particles appear to remain somewhat equal in number throughout the three wear in samples as opposed to the diminishing effect found in bearing #3. This again is attributed to the nature of the test. No other signs of abnormalities were noted. 5.3.2. Normal wear Transition occurred to normal wear after 10 MIL REV point and continued to the 120 MIL

REV sampling point where an unstable wear condition initiated. The continuing presence of wear in particles indicates that the removal /di smantl ing/regreasing procedure reintroduces a wear in type condition momentarily after each start up. The ratio of large-to-small parti- cles decreased somewhat from wear in, but remained high. Significant amount of cutting

(abrasive) wear was observed at the 80 MIL REV sampling point. Laminar particles increased significantly in proportion to rubbing wear.

5.3.3. Wear out After 120 MIL REVS sampling point, an unstable wear rate developed. The lubricant be- gan to slightly degrade, causing problems in obtaining accurate particle analysis. An interesting observation was made, in light of the test procedure, the grease appeared to degrade as in bearing #1, yet bearing #5 was regreased after each sample. Severe wear

particles and laminar particles increased in major dimension, yet their total numbers remained stable until the termination point in the test. 5.3.4. Optical and SEM inspection

Optical and SEM inspection by SKF personnel revealed excessive denting and pitting had taken place on the wearing surfaces, though no bona fide failure had occurred. Replacement

of bearing would be recommended.

5.4. Set III bearings (no. 06) Bearing #6 of Set III ran to 52 MIL REVS where it developed a classical spall failure.

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5.4.1. Wear in Wear in occurred between 1 and 10 MIL REV. A large number of particles were observed.

A noticeable absence of wear in type particles was noted in all wear in samples. The ratio

of large-to-small particles was lower than observed in other bearings, though the total number was higher than bearing #5 despite the dismantling of the bearing. Severe wear

and abrasive wear particles were observed. The increase of laminar particles was greatly accelerated as opposed to other bearings.

5.4.2. Normal wear

Transition to normal wear occurred after 10 MIL REV and continued to 20 MIL REVS. A dramatic increase in laminar particles occurred with a corresponding decrease in rubbing.

No wear in particles were observed. The ratio of large-to-small particles decreased to within normal size. 5.4.3. Wear out

An unstable wear state/condition occurred after the 20 MIL REV sample point. A marked

increase in total number, type, and size of all particles. The size and amount of abnormal wear particles (fatigue and severe wear) were easily detected. Slight temper coloration was

noted on the severe wear particles. It was evident that on abnormal wear state/condition

had or was about to occur.

5.4.4. Optical and SEM inspection

Optical and SEM inspection by SKF personnel revealed that a spall developed on the center tract o

f the inner ring. Thermal coloration occurred on the leading edge of the

spall. Debris generated dents, large in size, were observed as were several pits. Re- placement of bearing would be recommended.

6. Grease Lubricated Taper Roller Bearings

6.1. General discussion

Research is presently on-going in the bench- testi ng and analysis of the resulting used grease samples of grease lubricated taper roller bearings. The modif ied-for-testing taper

roller bearings were tested and sampled in a manner very similar to the grease lubricated

ball bearing test previously discussed. During the initial startup of the testing, a degradation problem was encountered. The grease utilized was the same as specified for

the ball bearing test. A reevaluation of the grease was performed and several types of greases were tested to determine a suitable replacement. A paraffinic mineral lithium

soapbased grease was selected. This grease was then implemented and performed satisfactorily. The wear particle analysis is presently being performed and preliminary indications are that the wear state/condition of the grease lubricated taper roller bearings

can be ascertained in much the same manner as the ball bearings.

7. Summary Ferrographic analysis has been shown to be useful in evaluating the wear/state condition

of grease lubricated components. The major achievement was the successful application of dissolving the grease utilizing a solvent mixture and making ferrograms of equal quality as to that found in oil analysis. The types of wear particles found in used grease samples are comparative to those found in oil lubricated systems. Work is presently being performed on grease lubricated taper roller bearings, similar to the test conditions utilized in this

study.The analysis of the grease samples was qualitative vs quantitative. Due to the uneven distribution of wear particulate in the grease and the relatively small amount of grease

used in making the ferrograms. The primary emphasis was placed upon size distribution, morphology and elemental composition.

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The results of the ferrogram analysis showed a good correlation to those of the SKF personnel in terms of monitoring the wear state/condition of the bearings throughout thei

life. However, the on-condition monitoring of grease lubricated components in the field,

is complicated by the physical location of the components and inaccessibility by main- tenance personnel to remove grease samples. Where accessibility is no problem, this technique is highly recommended. As it appears presently, this analysis technique seems best suited to the examination of grease obtained from dismantled grease lubricated com- ponents or in design applications.

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National Bureau of Standards Special Publication 584. Proceedings of Joint Conference

on Measurements and Standards for Recycled Oil /Systems Performance and Durability held at

NBS, Gaithersburg, MD, October 23-26, 1979. (Issued Nov. 1980)

ENGINE CONDITION DEFINED BY OIL ANALYSIS

Clifford G. Salvesen

Mobil Oil Corporation

Technical Service Laboratories

P. 0. Box 1027 Princeton, NJ 08540

In this paper we discuss the technology used to monitor engines and lubricant condition. The type equipment monitored includes gasoline,

diesel , dual fuel, and natural gas engines. The analytical procedures

for used oil analysis include: 1) infrared spectrophotometer, 2) mem- brane filtration, 3) direct reading spectrometer, and 4) automated

viscosimeter. For optimum benefit from the oil analysis data, it is necessary to have good background data on the oil being tested. Without

this information, less accurate readings and interpretation of the data

will result. Control limits utilized for the programs are also critical. These limits are developed from a statistical study of the data generated,

field tests conducted on the oils, plus feedback from the equipment

builders and users.

1. History of Oil Analysis

The main objectives for any oil analysis program is to measure oil contamination, oil degradation, and wear metals. A variety of procedures may be used to define these parameters

including viscosity, flash point, neutralization number, insolubles in pentane and/or toluene

by centrifuge, and wet chemical or spectrographs (wet plate) measurement of metals. These

tests were used for many years and served well, but were somewhat slow, for oils containing

no or low additive levels. With the advent of highly dispersant engine oils it was noted

that two of these tests were unreliable. These are neutralization number and insolubles.

The neutralization number may be troublesome because instead of titrating for acid-oxy

materials, the titrating solution may react with the additives. Insolubles results are questionable because the centrifuge procedure does not always spin out all of the insoluble

materials.

2. New Methods

In view of the above mentioned problems, new procedures were investigated. It was

found that infrared, membrane filtration, atomic absorption, or direct reading spectrometer,

and automated viscosity offered better and faster means for analyzing used oils. The data obtained from these procedures follow in table 1.

Equipment

Membrane filtration

Atomic absorption or direct reading spectrometer

Automated viscosimeter

For Defining

Water, oxidation, nitration, nitro compounds,

glycol, gasoline fuel dilution and miscellaneous contaminants

For total insolubles and dispersancy charac- teristics

For key metals

For rapid viscosity measurement

133
Additional information on some of these procedures and their development was given in SAE papers #680759 and #730745 published some years ago by personnel from the author's company.

3. Discussion of Equipment

3.1. Differential infrared analysis

The infrared equipment has been redesigned in recent years to provide more rapid, yet

accurate, results. In our laboratory, we have modified various equipment to automate much

of the procedure. The principal differences between our units and conventional infrared equipment are as follows:

1) Automated sample feed system — We use a 200 position feed tray, a sample dipper,

a positive displacement pump, a "self-cleaning cell" and the necessary electronic equipment to operate the system.

2) Automatic reference system ~ Up to 6 different reference oils can be used and the equipment is programmed so that reference cells change as the oil types change.

In practice we sequence all of the same type oil samples, and at the end of the

run, the reference automatically switches to the designated product for the next series of oils. When all 200 samples are tested, the unit shuts itself down.

3) Spectrophotometer modifications — Mechanical and electrical changes have been made to speed up the recording in wavelengths of low interest and to slow it down

for key areas, and

4) Auxiliary recorder — The output of the spectrophotometer is fed to a flat-bed recorder whose speed is adjusted to compress the spectrum so that about 360 samples are displayed on a single roll of chart paper.

In the following table we list the materials routinely tested for, and give their wavelength assignments and units of measurement. Table 2. Identification of infrared bands Type of Service Reported Wavelength, pm Nature of Component Diesel Gas as 2.9, 6.05 Water (bonded) X X % Volume

5.85 Oxidation X X A/cm

a 6.1, 7.9, 11.6 Organic nitrates - X A/cma 6.4 Nitro compounds - X A/cm

12.4, 12.8 Gasoline dilution X % Volume

9.3, 9.7 Ethylene glycol X X % Volume Other bands Unusual contaminants X X A/cm Absorbance per centimeter of cell film thickness.

3.2. Membrane filtration

This procedure is used to define the amount of insoluble materials above a certain critical size, rather than total insolubles. A measure of total insolubles may be meaningless

in terms of deposit drop-out or filter plugging tendencies, even at a high content, as long

as their size remains well below the critical level. Through laboratory and field testing

of various oils, we have defined the critical membrane size to be utilized. The procedure for membrane filtration is to dilute the oil with pentane and filter the mixture through a preweighed membrane. The insolubles are reported as weight percent. We

use a multiple sample membrane filtration apparatus for the filtration and an electrobalance

with digital readout for weighing.

184
3.3. Viscosity determination

An automated Brookfield type viscosity unit has been developed for viscosity measurement. The unit is temperature controlled for the specified test temperature, i.e., 210 °F for most oils and 100 °F for some. It uses an automated sample feed system similar to

that described previously for the ir. A known oil is checked periodically and all torque

readings are recorded on a strip chart. Calibration charts have been prepared for con- verting the strip chart readings to centi stokes and/or SUS. 3.4. Metals determination

For most used oils we use a direct reading spectrometer. This unit provides a direct

readout in ppm for 25 elements. Background data on the oil being tested is fed into a computer so that we minimize errors. Standard reference materials available from the National Bureau of Standards are used to calibrate the instrument.

4. Used Oil Control Limits The analytical equipment described previously has the ability to accurately define the condition of a variety of oils. However, to be meaningful, accurate control limits are re- quired for a variety of engine types and service. The procedures used to develop the control limits are as follows:

1) Compile background information on the base stocks and additives,

2) conduct field tests to stress the lubricant to a maximum degree,

3) investigate field failures where a piece of equipment has been monitored,

4) obtain feedback from equipment builders on the metallurgy of the equipmnt, and

5) statistically analyze the used oil data to establish normal and abnormal conditions.

4.1. Base stocks and additives

The base stock and additive chemistry must be factored into the key tests.

4.2. Field tests We select a variety of equipment and applications to cover a range of operating conditions. Used oils from the units are checked periodically to follow trends; i.e., as noted

by ir changes from new oil. Metals, viscosity, make-up oil, etc., are all factored into our

findings.

4. 3. Field fai lures We work closely with our field engineers to obtain data on any field problems. Our laboratory supplements the field observations with deposit analyses, metallurgical examination of failed parts, etc. 4.4. Equipment builder data

Our field engineers work closely with equipment builders to obtain metallurgical and

other key data. Furthermore, they keep us advised of any modifications, service tips, etc., that will aid in defining equipment performance through used oil analyses.

4.5. Statistical studies Periodically, the used oil results, particularly wear metals, are reviewed to define

normal, borderline, and excessive ranges. Distribution curves are plotted showing total percent of samples vs ppm of a metal. All areas below the inflection point are considered

normal. This usually occurs at about the 85 percent point. The borderline area is selected

as the 85-95 percent range and the excessive range covers those samples above the 95 percent

range.

185
5. Typical Program in Action

Several examples of the use of our analysis system are given below:

5.1. Example A - cracked head Excessive water, glycol, copper and lead were found in an oil drain sample as noted

in the following analyses. Sample information

Date received

Lab number

SAE grade Service mi/hr

Oil Filter

Engine Make-up qts Date sampled

Oil analysis

Date reported

Vise. @ 210 °F SAE grade

Dil. Water

Glycol

Oixd. , A/cm

Nitr. , A/cm

Spectrograph, ppir Iron Silicon (dirt) Aluminum

Copper

Lead Chromium

Action codes

9/16

032

125 125 2210

40 9/10 9/17

60

30 Pass

Pass Pass

6

7 1035

3

0

10/21

045

10/9 10/26

64

30 Pass

Fail 3 Fail

3

3

11/2

004

5050 2380

8 10/28

11/5,

73

a 403 Pass

Fail

3 Fail

3 15

59

11Ua 176

3 97

a 64,5,11,13,14

55

11 165

3 81

3

62,4,5,11,13,14

Action required After the October 9 sample results were obtained, the customer was advised by telephone.

The next analysis on a sample taken three weeks later confirmed the earlier findings and the customer was again alerted. The Maintenance Superintendent ordered the unit out of service. Inspection of the engine showed a cracked head had caused the water and glycol contamination. Repairs were

made and the unit returned to service before more extensive damage had occurred.

5.2. Example B - cracked exhaust manifold

Oil analyses from June through August, as noted below, showed a progressive increase in viscosity from 66/69 SSU @ 210 °F (SAE 30) to a high of 184 SSU @ 210 °F (over SAE 50).

Date received 6/11 7/1 7/24 8/13 8/20 9/2

Lab number 002 021 017 012 011 078

SAE grade Service mi/hr

Oil 138 193 152 155 129 155 Filter 138 193 152 155 129 155 Engine 2557 2764 2879 3165 3236 3391 Make-up qts Date sampled 6/6 6/28 7/18 8/10 8/15 8/27

186
Oil analysis

Date reported

Vise. @ 210 C F SAE grade

Oil. Water

Glycol

Oxid. , A/cm

Nitr. , A/cm

Spectrograph, ppm

Iron Silicon (dirt) Aluminum

Copper

Lead Chromium

Action codes Action required

6/12

a 7/2

a 7/27

a 81

a 97

a 100

40 50 50 Pass Pass Pass Pass Pass Pass

1

in a 7 28 20 16 10 10 9 26 21 33 4 4 2 2,14 2,14 2,14

8/14 8/24 9/3

108

a 64

50 50

a

30 Pass Pass Pass Pass Pass Pass

I I

43 37 47

9 j

19

10

X

9 13 31 22 23

4 3 3 2,14 2,14 0

The customer's maintenance people were alerted and after several inspections, located a crack in the exhaust manifold. The lowering of exhaust pressure caused the turbocharger to slow down, starving the engine's air needs. This incomplete fuel combustion caused soot to build up, thereby boosting viscosity. After repairs were made, subsequent oil analyses

showed normal viscosity levels.

5.3. Example C - broken case gasket

In this instance, oil analyses, as noted below, showed excessive silicon, iron and

chrome. This indicated the possibility of a low pressure air leak. Sample information

Date received 4/19 5/3 5/20 6/18 7/29

Lab number 079 053 027 049 093 SAE grade 30 30 30 30 30 Service mi/hr

Oil 136 106 105 123 98 Filter 136 106 105 123 98 Engine 4794 — — — —

Make-up qts 72 20 32 40 32 Date sampled 4/16 4/29 5/17 6/16 7/27

Oil analysis

Date reported 4/21 5/5 5/24 6/22 8/3

Vise. @ 210 °F 63 62 64 62 62 SAE grade 30 30 30 30 30

Dil. Pass Pass Pass Pass Pass Water Pass Pass Pass Pass Pass Glycol Pass Pass Pass Pass Pass

Oxid.

Nitr.

,, A/cm

A/cm —16— —

2 —12—

Spectrograph, ppm

Iron 164

a 207

a 221a 165

a 61 Silicon (dirt) 99

a 107a 58a 45

a 19 Aluminum 48 50 30 29 18 Copper 11 20 14 12 9 Lead 19 22 18 20 30 Chromium 39

a 41a 26a 19 10 Action codes 8,9,12,13,14 8,9,10,12,13,14 8,9,12,13,14 7,8 0 Action required

187
The customer checked all fittings, couplings, etc., between the air cleaner and turbo- charger on a regular basis and they were found to be in order. Yet the silicon values remained high. It was decided to take the unit out of service until the leak could be found hoping to avoid a "major" engine failure which would have cost the customer about $6000 to repair. After considerable checking, a leak was discovered coming from a broken gasket between

the air case and main body of the turbocharger. Using the new procedures described herein, our laboratories are able to analyze a wide variety of lubricants from engine and nonengine applications. This is accomplished with significant reductions in manpower and oil analysis time. We find that we can handle about ten times as many samples per man hour using these new procedures compared to the older methods. Reporting time for these samples varies from the same day as the oil is received, up to ten working days, depending upon the oil application and variety of tests required. Most

of the reports are issued within three to five days after sample receipt.

1 88
Session 5 BENCH TESTS FOR OIL EVALUATION

189

National Bureau of Standards Special Publication 584. Proceedings of Joint Conference

on Measurements and Standards for Recycled Oil /Systems Performance and Durability held at

NBS, Gaithersburg, MD, October 23-26, 1979. (Issued Nov. 1980)

ENGINE OIL EVALUATION THROUGH BENCH TESTING

S. M. Hsu Tribochemistry Group

Chemical Stability and Corrosion Division

National Bureau of Standards Washington, DC 20234

1. Introduction Automotive crankcase oil performance is defined by field tests and laboratory engine

sequence tests. In MIL-L-46152 specifications, passing results in five engine tests 1 are required for oil qualification. These are: 1) IID - rust protection; 2) HID - oxidation

resistance, wear protection, oil consumption; 3) VD - low temperature dispersancy, wear

protection, deposit forming tendencies; 4) L-38 - copper-lead bearing corrosion resistance,

shear stability; and 5) 1H2 - ring sticking, wear, piston deposits in diesel engines. The engine operating conditions for some of these tests are shown in tables 1, 2, and 5. These

engine tests are generally time consuming and expensive. For this reason, various forms of

small scale laboratory bench tests are developed and used to screen oils for quality and consistency. There are different opinions regarding the value of the bench tests. Some suggest the bench testing provides an effective tool to understand the underlying mechanisms

of oil performance. Some suggest they are of little value because the engine test is the

final judge of quality, and correlation between the engine test and bench test is difficult

to develop and maintain. One contributing factor to these two opposing viewpoints is the proliferation of the number of bench tests. Some tests are developed with care and insight,

some are outdated and obsolete but still in use. There are few standard procedures and even

fewer published correlations. This study is the initial step to examine various kinds of bench testing against a set of criteria and to eventually provide guidance for their effec- tive use. Within this context, this paper will examine the basic mechanisms of engine oil degradation and deposit formation. Any bench test, to be useful, must simulate some aspects

of the basic mechanisms. Various bench test procedures are then described in detail.

2. Oil Degradation Mechanisms in Gasoline Engines There have been a number of changes recently in engine design, fuel composition and driving patterns. As a result, the sequence engine tests have been changed from IIC, IIIC,

VC, 1H to IID, HID, VD, and 1H2. These changes are compared in tables 1 and 2. The fol- lowing discussion on oil degradation mechanisms are based on older engine tests and opera- ting conditions 2

. Since bench tests are used to simulate engine tests, it is important to examine also how oils degrade in an operating engine. There are a limited number of studies published

in the literature [1-10] 3 and basic mechanisms of oil oxidation and deposit formation are

not clearly understood. In summary, the engine can be viewed as two chemical reactors in series. The first one is at the piston cylinder liner area where a thin film of oil is subjected to high temperatures, high shear stress and to hot combustion gases. The second detailed description of test procedures and specific engines employed are given in ASTM

Publications STP 315 G and STP 509 G, 1916 Race Street, Philadelphia, PA.

2 The Army Fuels and Lubricant Laboratory at SWRI is currently in a cooperative program

with the NBS Recycled Oil Program to re-examine the degradation mechanisms in current

engine and test procedures.

3 Figures in brackets indicate the literature references at the end of this paper.

191
reactor is the oil sump where temperatures range from climactic regime to 100 °C. Here con- tamination by water, fuel dilution, dust, blow-by gases and the reaction products from the first reactor (referred to as the sludge and varnish precursors) occurs. Subsequently reac- tions take place to form sludge and varnish. Table 1. Comparison of engine operating conditions between I I I C and HID.

Engine

IIIC 1967 Oldsmobile

425 CID HID

1977 Oldsmobile

350 CID

Fuel 550 Gal GMR995 0.072% S

o . y cc/ ga i rD

C n pPf) RDM 3000

Load, HP 100

Oil sump temp, °F 300° Same Jacket temp, °F 240°

Max. oil ring temp, °F 450° - 500° Piston skirt temp, °F ^300°

Test time, h 64 64

Table 2. Comparison of engine operating conditions between VC and VD.

VC VD

Engi ne 1970 Ford

302 CID 1977- 2.3

79 Ford

litre

Fuel 1000 gal MS08 0.10% S 2.8 GM/qal Pb525 gal

0 Phillips J .015% S Sequence 1 2 3 1 2 3 Time, h 125 75 45 120 75 45 Speed, RPM 2500 2500 500 2500 2500 750

Load, HP 86.6 86.6 2.0 33.5 33.5 1 Oil sump temp, °F 175° 200° 120° 175° 187° 120° Jacket temp, °F 133° 167° 112° 135° 135° 120° Test time, h 192 192

Principal oil degradation occurs in the piston ring zone and on the cylinder liner

area. Oil is being pumped to the various parts of the engine such as rocker arms, valve

train and cam and lifters where the temperature lies between 180 to 210 °F. The oil sup- plied to the piston and cylinder liner is subjected to far more severe conditions. Several things happen to the oils: 1) Some oil is left on the cylinder liner to face the combustion

flame front (temperature of the oil ~370-425 °C). The light ends in the oil are vaporized. Heavier fractions are oxidized and mixed with the high MW fuel components (fuel additives,

lead salts, lead scavengers, soot and unburned but oxidized gasoline fractions). This oil

is then scraped by the piston ring and returned to the sump. 2) Some oil is circulated

through the rings. Temperatures on the order of 200 to 260 °C are possible depending on the operating conditions and the type of engine. The oil is oxidized or nitrated by the high temperatures and the blow-by gases (N0

x> 02 , H 2 0, CO, C0 2 , C). Polished iron of the rings under these temperatures is a very good dehydrogenation catalyst.

192
Fuel blow-by probably is the main cause for deposit formation. The blow-by gas is made

up of combustion gases and unburned fuel components. Anderson [11] reported in a laboratory

engine that out of the 1000-3000 ppm NO measured in exhaust gases (amounts vary with

air/fuel ratio, compression ratio, speed), only 40 percent is left when the blow-by gas reaches the crankcase. This suggests that 60 percent of the N0

x reacts with fuel components

and oil in the ring zone. The resulting nitrocompounds and nitrates in the oil react with

oxidized hydrocarbons to form sludge and varnish. Spindt [8] operated an engine in a nitrogen-free atmosphere and obtained essentially clean pistons. The olefins and aromatics in the fuel have been identified as the main deposit-forming

components. Several studies [1,2,3,4,6] have identified that the olefins (C2 -C6 ) in the

fuel react with N0^ to form a, 8 nitro-nitrates which are the sludge and varnish precursors. Radioactive tagging experiments with benzene as fuel demonstrate that 95 percent of the sludge carbon stems from fuel. Aromatic components in the fuel (Cg-Cn alkyl benzenes

and alkyl indanes) have also been shown to effect varnish formation in engines. Engine test conditions are presented in tables 1 and 2. The chemical composition of the deposits are shown in tables 3 and 4. Considerable fuel component influence is evident. Table 3. Composition of gasoline engine deposits. Varnish from reference [9]. Varnish

Piston Varnish Other Varnish (Acetone Soluble)

c 20- 75% Wt C 67- 76%

H 2- 10 H 8- 10

N 1- 3 N 1- 3

S 1.5- 11 S 1- 2 Br 1- 5 Br 2- 5 CI 1- 8 CI 1- 4 Pb 5- 16 Pb 5- 6

0 11- 16 0 2- 6 MW 300-350 MW 600-650

Table 4. Composition of gasoline engine deposit. Sludge from reference [5]. Sludge

Solids 16-32% Wt Liquid 64-80%

Others 4%

Solids

Lead halides 30 Zinc 4 Phosphorus 0.3 Sulfur 2 Fe 1

Si 0.1

Oil insoluble oxidatign

product 40

a 0=13-15%, H=8-10%

C=60-70%, N=1.5%

Certain additives play a role in forming engine varnish and sludge deposits. Sulfonates are used as rust inhibitors and detergents; under oxidizing conditions, they react with water and oil oxidation products giving rise to polymerization and gel formation.

Zinc dithiophosphate (ZDDP or ZOP), while inhibiting oxidation and preventing wear and

193

- 40% Wt

- 9 -0.6

- 4

- 2

- 1

Liquid

Oil Fuel 60 - 4

-
seizure, decomposes under a thermal and acidic environment to give oil insoluble products. Viscosity index improvers (VII) are high molecular weight polymers used to increase oil viscosity at high temperature by uncoiling their polymeric structures. At the same time, VIIs are very susceptible to oxidation and chain scission via free radical oxidation. These additives, when properly balanced, can give maximum benefits while minimizing their contri- bution to forming deposits. A good example is that high levels of ZDDP give excellent oxida- tion control but poor sludge ratings. Summarizing, the deposit formation in gasoline engines heavily depends on the fuel composition, blow-by composition, amount of blow-by, temperature and oil oxidation. This

is summarized in figure 1. From the standpoint of bench test development, the basic mech- anism can be broken down as follows: 1) High temperature oxidation (piston ring zone and cylinder liner); 2) thermal decomposition (piston ring zone and cylinder liner); 3) hydrolysis; 4) catalysis by: nitrated C 2 -C6 olefins; blow-by gases N0

x (S0x , N0x in VC); lead salts; iron and wear metal; and aromatic fuel components; and 5) absorption, ad- sorption and polymerization.

Lead Salts

Sulfur, Nitrogen Compounds

Piston Skirt Adsorption & Reaction

Polymerization

High Temp Varnish on Piston Skirts

• Fuel Combustion

Blowby

I NO + 02 + H2 0 + HC

+ CO + CO, + C

- Ring Zone

Oil Absorption NO,

Oil Oxidation, Catalysis & Nitration

Oil Insoluble Products & Oxidized Monomers

& Nitrate Esters

Carbon Varnish - Lead Salts Sludge

Precursors

Inorganic

Solids

}

Crankcase

Oil Absorption

NOx

a, p Nitro-Nitrates

. 150-200 Avg. MW

- Metal Surface Adsorption &

Reaction

Surface

Actiwe Polymers

Sludge Low Temperature

Varnish Deposit

Figure 1. Deposit formation mechanism in gasoline engines.

194
3. Deposit Formation Mechanism in Diesel Engines

The formation of diesel engine deposits can be ascribed to high temperature oil degrad- ation in the presence of strong acid and nitrogen oxides. Most of the diesel specification

engine tests are single cylinder laboratory engines as shown in table 5. High sulfur diesel

fuel is used. Significant amounts of S0

x are generated in the combustion gases in addition

to NO . There are many studies on the mechanism of deposit formation in diesel engines

[11-17]. Conclusions are: 1) diesel piston deposits contain oxyacids derived from the lubricant and 2) sulfur acid attack on the lubricant promotes deposit formation. Table 5. Diesel engine test conditions.

L-38 1H2 Labeco Single Caterpillar SC

Engi ne Cy 1 i ndGr EncjinG Supercharged

42.5 CID 133.5 CID

50 gal 1100 gal diesel

Fuel I S0~ octcinG 3.0 cc/gal Pb 0.4% S CnonH D DM opeea, Km

Load, HP Adj to 4900 BTU/min

Oil sump temp, F 275-290 180 Jacket temp, F 195

Max. oil ring temp, F 620 Piston skirt temp, F ^300

Test time, h 40 480

Some studies showed that the degradation of oil and additives under high temperature

acidic environments is the main cause for ring sticking. The temperature at the ring zone

has been measured by many. Earlier studies using thermocouples revealed temperatures in the vicinity of 230 °C. Recent studies [18,19] suggest much higher temperatures (325-360 °C). These temperatures are tabulated in table 5. The overwhelming presence of combustion soot is another important factor in deposit

formation. The diesel fuel, even under supercharging conditions (excess air) is only partially burned. Soot particles with sizes ranging from 100 A to 500 A are formed by condensation of C 2 , C 3 and aromatic fragments in the fuel. Subsequent agglomeration in- creases the sizes to 0.005-2.0 urn. Under highly loaded conditions, the excess air is reduced and soot formation increases. In a typical used oil, the soot could range from

1 to 4 percent depending on the fuel consumption, engine conditions, load, etc. The presence of these soot particles provides a large liquid-solid interfacial area. Surface

active additives such as dispersants, detergents and zinc dithiophophates agglomerate at the interface via adsorption, thus reducing the effective additive concentration.

Piston varnish formation in diesel engines is influenced heavily by N0

x> As in gasoline engines, N0

x promotes the formation of nitrate esters which interact with oil oxidation products forming polyester and polyether type structures [17]. In diesel fuels, the

small amount of light olefinic or aromatic components reduces the concentration of nitrate

esters formed. Oil oxidation products play a more important role. Hydroperoxide produced

from oil oxidation promotes the formation of H 2 S04 from S02

. The sulfuric acid, in turn, promotes poly-condensation reactions of the oxidized species to higher MW resins. These

resins, upon adsorption on the piston skirt, polymerize under N0

x to give varnishes. The

same resins also act as organic binder in the top ring groove area. Experiments with

195
tritium- labeled base oil in a Petter AVI show that 90 percent of this bonding agent is derived from the oil [17]. Model hydrocarbon oxidation studies at 300-400 °C (572-752 °C) have yielded polymeric material similar to that found in engine piston deposits. These oxidation conditions correspond to air attack on the oil at the ring zone temperature and

to preflame combustion of the fuel (cylinder liner - oil sump circulation) for a brief

period. The presence of sulfur compounds and N0

x markedly increase the yield of this polymeric material which can be formed from epoxides, hydroxy acids, diols, and diacids. A schematic diagram illustrating diesel deposit formation is shown in figure 2.

incomplete Combustion

Oxidation/Thermal Degradation via Ring Zone Circulation

Hydroperoxide & Oxidized Products

Carbon Deposit Figure 2. Diesel/engine deposit formation mechanism.

4. Bench Tests There are many bench tests currently in use in the industry. Generally the tests ad- dress some specific aspects of oxidation, dispersancy, and deposit formation tendencies. The following sections will describe some selected bench test procedures and compare them

to the engine oil degradation mechanism previously discussed.

In oxidation area, the most commonly available tests are: Rotary Bomb Oxidation Test

(RBOT, ASTM D-2272), Turbine Oil Oxidation Test (TOOT, ASTM D-943). The test procedures are shown in tables 6 and 7. These two tests are developed for industrial oils but widely used

in oil industry for other applications, sometimes with modifications. From the standpoint of chemical reaction conditions in an engine, both the RBOT and TOOT test conditions differ sig- nificantly. The data from these two tests, however, reflect the oxidation stability under

196
metal catalysis and water contamination at the test temperatures. Extrapolation of data to automobile operating conditions where oxidation, nitration, fuel composition, blow-by gases

and metal catalysis are important over a wide range of temperatures, is difficult and misleading. Variation of the standard RBOT and TOOT test conditions is often used to improve

the simulation. Table 6. Rotary bomb test. Pressure Temperature

Catalysts

Water jacket Rotation

= 90 psig - 180 psig

= 130 °C - 150 °C

2 = Copper wire (154 cm ) 5 cc of water

= 50 gram

= 5 cc - 100 RPM PARAMETERS MEASURED

Time - pressure relationship

Table 7. Turbine oil oxidation test (TOOT). Temperature = 95 °C Overhead condenser = yes Catalysts = copper & iron wire

= 60 cc of water

Oil = 300 cc PARAMETERS MEASURED

Number of test hours for oil to reach 2.0 TAN

SI udge Catalyst weight

The Ford Modified Oxidation Test [20] is shown in table 8 and figure 3. This test uses

metal coupons for catalyst under vigorous stirring. The temperature is in the mid-range of engine operating temperatures. The M0RC0 Oxidation Test [21] shown in table 9 is similar

except at slower stirring speed and shorter duration. Both tests have a fixed duration. In this type of testing, the sampling frequency becomes an integral part of the test. As shown

in figure 4, if samples are taken at point A, the ranking of the oil will be different from point B. At point C, the two oils will not show any difference. This is an important point. Bench tests are useful only when they are used correctly. In measuring oxidation stability,

it is important to plot the parameter measured as a function of time to avoid misinterpretations from discrete point comparisons.

Some new and exciting works are currently being pursued at several laboratories. Mohoney and Korcek [22,23] at Ford Motor Research have published some work on free radical titration procedure by which the anti-oxidant reserve or capacity can be measured. This

197
Table 8. Ford modified oxidation test. Beaker oxidation test Conditions:

Oil = 275 cc Temp. = 135 °C Catalyst = Iron and copper strips Duration = 300 hours Stirring speed = 1000 RPM Parameters measured: Viscosity increase Pentane insoluble

TAN

Figure 3. Ford modified oxidation test. Table 9. Morco oxidation test.

o Open beaker type test with stirring Temperature = 135 C Catalysts = Copper and steel strips Stirring speed = 300 RPM Duration = 72 h

o Parameters measured Viscosity at 100 F and 210 F Pentane insoluble

TAN

TBN

198
Time

Figure 4. Viscosity increase characteristics in oxidation tests.

has the advantage of measuring both the anti-oxidant present in the oil as chemical additives and the "natural inhibitors" in the oil itself. This parameter measurement in theory is much better than the carbonyl band measurement by infrared or viscosity increase,

TAN etc. Klaus et al . , [24] at Pennsylvania State University, under a research contract

from the Recycled Oil Program, are developing a rapid, thin-film, micro-oxidation test

procedure. The oil film rests on a hot steel surface as shown in figure 5 and the molecular weight change is monitored by gel permeation chromatography. Initial results are very

encouraging. Wing Tsang et al . , [25] at the National Bureau of Standards, also under a re- search contract from the Recycled Oil Program, are examining the use of high pressure dif- ferential scanning calorimetry as a quick, precise measurement of lubricating oil oxidation

stability. Oxidation induction time, heat of reaction, and the temperature under which

oxidation occurs can be easily measured. This technique, if successful, could provide a sound theoretical background, as well as a practical oxidation bench test procedure.

5. High Temperature Stability Tests

In high temperature stability testing for automotive oils, the most prevalent tests are

panel coker and hot tube. In the panel coker test small droplets of oil are continuously

splashed on a hot metal panel as shown in figure 6. The panel is usually kept at 600 °F (316 °C) and after two to six hours of operation, the panel deposit is rated for lacquer

deposit or the weight gain is determined. Sometimes, heated gaseous environment of N02 and S0 2 is introduced. The hot tube test [26] consists of bubbling oil with air or N02 upward through the inside of a capillary glass tube kept at high temperatures as shown in figure 7. The test is used to simulate IIIC, 1H, and 1G engine tests. For IIIC simulation, the test is run at 395 °F with 2000 ppm N02

. For 1H simulation, the conditions are 495 °F with air and 530 °F for 1G test. The oil flowrate is kept at 1/3 cc/h for sixteen

hours. The glass tube is then rated against standards for deposits. Generally, these two

tests simulate the high temperature ring belt conditions of 1H, 1G engine tests. Correlation with weighted total deposits (WTD) is fair, partly because the WTD itself is not too repeatable in the engine tests. When compared to the diesel deposit mechanisms as shown

199
Figure 5. Pa, state micro-oxidation test apparatus.

in figure 2, the acidic environment of S02 , S03 , and H 2 0 in the presence of soot is not being simulated. These two tests reflect the high temperature stability of oils under oxidizing conditions. Used oil analysis from 1H and 1G engine tests suggests nitration is the predominant reaction path.

In the panel coker test, the cleanliness and surface roughness of the panel are important. The difference in deposits between aluminum and steel panels is also significant. Variation in operating temperatures, and the way the oil is splashed onto the panel are some of the common modifications. Some experimented with intermittent oil splashing to more closely simulate the engine operations. Detail correlation data of these tests and their modifications are not available in the public domain.

200

6. Dispersancy Tests There are more tests on dispersancy than any other area. The most commonly used tech- nique is the blotter spot test. It consists of either coking the oil with additives or put- ting some additives into a fixed amount of standardized used oil/sludge. The oil is then spotted on blotter paper or chromatograpic paper. After a fixed period of time, two concentric circles are formed as the sludge/used oil diffuses out radially. The ratio of the sludge ring (the inner black ring) over the oil ring (the outer transparent ring) indicates

the degree of dispersancy, i.e., the ability to keep oil insoluble materials in suspension. Carbon black is sometimes added to the oil and after heating at high temperatures, the

oil is spotted. Some procedures use elaborate heating cycles to produce so-called "organic

binder" to aggregate the fine carbon black in the oil. Generally, the spot method is sensi- tive to water. If used oil is used, it should either be dried or the water content adjusted

to a fixed level

.

The basic requirement in controlling sludge (oil insoluble oxidation products) is the ability of the oil to solubilize fine dispersions either in colloidal or mi cellar form. This kind of test then offers insight into the relationship between molecular structures of the additive molecules and the ability to disperse. Various forms of oil insoluble solids

are employed: carbon black, pyruvic acid, rhodamine C dye, titanium oxide, pentane insoluble, and sludge form used oil. Generally, the ability of the additive to disperse these solids

in stable form is measured. The results are often expressed in percent dispersed or in the case of acids, the amount of base used in titration. These methods are similar to blotter

spot tests. Bowden, Dimitroff et al . , [26,27] used electrophoresis technique under a microscope to study the mobility of sludge particles under the influence of electric charge. Blagovidor

et al., [28,29] recently developed a technique to measure the el ectroconducti vity properties

of oils. He compared the el ectroconducti vity of an oil containing the dispersant additive

to an oil containing the same additive plus 2 percent lamp carbon black (specific surface of 97 m

2 /gm). By plotting the ratio of the electroconductivities versus additive concentration

he was able to define the critical micellar concentrations for various forms of additives. This technique holds promise to elucidate the basic mechanisms of di spersants/detergent.

7. Discussion and Conclusions

Bench tests are simple tools used to study a very complex phenomenon, the field test. Because of the enormous expenses and time involved in the field test, engine dynamometer

"bench tests" are developed. In time, these engine bench tests become prohibitvely

costly, laboratory scale bench tests are used. With each simplification step it is easy to forget the real objective of realistic simulation of field conditions. Table 10 summarizes

some of the characteristics of bench, engine, and field tests. Table 10. System comparison of bench test, engine test, and field test. Bench Test Closed system Short duration

Severe condition

Single aspect

Simple

No combustion

Exaggerated difference

Low cost

Engine Test Closed system

Short duration

Severe condition

Multiple controlled parameters

Complex Combustion

Strong difference

Costly

Field Test

Open system

Long duration

Mild condition

Multiple parameters

Very complex Combustion

Good difference

Expensive

202
In simulation tests, the most important question may be what conditions are to be simu- lated? In a very complex system, the question then becomes what are the "key conditions" to

be duplicated? In engine test simulation, the analysis of used oil and the understanding of

the steps or conditions that lead to the final state is essential for successful simulation. Most of the commonly used bench tests, when evaluated against the engine deposit mechanisms,

fail to duplicate most of the conditions. This may, in part, account for the poor reputa- tion of bench tests as a predictive tool in oil performance evaluation. Based on the results and discussions, the following conclusions may be drawn:

1) As a simulation model to predict performance, the existing bench tests

are useful but inadequate.

2) Properly used, bench tests may be useful in checking consistency of some aspects of oil quality. References

[1] Geyer, J., The mechanism of deposit formation and control in gasoline engines, ACS Symposium, New York (Sept. 7-12, 1969).

[2] Williams, A. L. , Lacquer precursor from a paraffinic lubricant traced by Carbon 14, ACM Symposium, New York (Sept. 7-12, 1969).

[3] Vineyard, B. D. and Coran, A. Y. , Gasoline engine deposit: I. Blowby collection and

the identification of deposit precursors, ACS Symposium, New York (Sept. 7-12, 1969).

[4] Coran, A. Y. and Vineyard, B. D. , Gasoline engine deposit: II. Sludge binder, ACS Symposium, New York (Sept. 7-12, 1969).

[5] Dimitroff, E. and Quillian, R. D. , Low temperature engine sludge - what? - where? - how?, International Automotive Eng. Cong., SAE paper no. 650255, Detroit (Jan. 1965).

[6] Dimitroff, E. , Moffitt, J. V., and Quillian, R. D. , Aromatic compounds in fuels iden- tified as main precursors of engine varnish, SAE Journal, 77, [7], 52-58 (1969).

[7] Berry, E. and Webster, A. B. , Emulsion formation in gasoline engines, J. Inst. Petrol.,

55, [544], 245-272 (1969).

[8] Spindt, R. S. , Wolfe, C. L. , and Stevens, D. R. , Nitrogen oxides, combustion, and en- gine deposits, SAE Trans., 64, 797-811 (1956).

[9] Dimitroff, E. , Mofitt, J. V., and Quillian, R. D. , Why, what, and how: Engine varnish, ASME Trans. J. Lubr. Tech., 406-410 (July, 1969).

[10] Rogers, D. T. , Rice, W. W. , and Jonach, F. L. , Mechanism of engine sludge formation and additive action, SAE Trans., 64, 782-811 (1956).

[11] Anderson, D. J., Mechanism of Engine Deposit and Wear. A progress report, Jap. Petrol.

Inst. Meeting, Tokyo, Japan (Oct. 1968).

[12] Verley, G. M. and Ovist, E. G. , The kinetics of crankcase oil contamination and piston

fouling in the diesel engine, ACS Chicago Meeting (Aug. 30 - Sept. 4, 1964).

[13] Rudinger, V., A model for the deposit formation on diesel engine pistons, Erdol und

Kohle, 27, [7] (1974).

[14] Spedding, H. and Noel, S. F. W. , Development of techniques for the analysis of piston

lacquers by infrared spectroscopy, Tribology (Feb. 1972).

[15] Denison, G. H. and Clayton, J. 0. , Chemistry and prevention of piston ring sticking,

SAE Trans., 53, [5], 265-268 (1945).

20 3
[16] Kreuz, K. L. and Love, R. F. , Role of sulfur in deposit formation and lubricant degradation in diesel operation, ACS Meeting, New York (Sept. 7-12, 1969). [17] Burgess, J. E. , Morris, A. L. , and Vickers, M. A., Chemistry of diesel deposits forma- tion - a study of model processes, ACS Meeting, San Francisco, CA (April 2-5, 1968). [18] Wing, R. D. and Saunders, 0., Oil film temperature and thickness measurements on the piston rings of a diesel engine, Proc. Inst . Mech . Engr . , 186 , 1-9 (1972). [19] Deen, H. E. and Schetelich, A. A., An improved method for measuring ring zone temperatures in Caterpillar test engines explains piston deposits, SAE preprint No. 542C

(1962).

[20] Manufacturing standards, MC/BJ 10-1, Ford Motor Company, Detroit, MI. [21] M0RC0 Oxidation Test, Motor Oil Refining Co., Lyons, IL. [22] Mahoney, L. E. , Korcek, S. , Hoffman, S. , and Willermet, P., The determination of the antioxidant capacity of new and used lubricants; method and applications, I&EC Product

R&D, 17, 250 (1978). [23] Willermet, P. A., Mahoney, L. R. , Kandah, S. K. , and Sever, A. W. , The application of antioxidant analysis to transmission fluid testing, SAE paper no. 790016, Detroit, MI,

(Feb. 26 - March 2, 1979). [24] Cvitkovic, E. , Reaction rate studies on ester oxidation, M.S. Thesis, Chemical Engi- neering Department, Pennsylvania State University, University Park, PA (1976). [25] Tsang, W. and Walker, J., Application of differential scanning calorimetry to the characterization of lube oils, Thi rd Conference on Recycled Oi

1

, NBS, Gaithersburg, MD

(Oct. 23-26, 1979). [26] Bowden, J. N. and Dimitroff, E. , Electrophoresis of dispersant lubricating oils, ACS Petroleum Chemistry Preprint, 6, N4, B-5 (1961). [27] Dimitroff, E. , Moffitt, J. V., and Quillian, R. D. , Dispersancy prediction by optical microscopy, SAE paper 600B presented at Philadelphia, PA (Nov. 1962). [28] Blagovidov, I. F. , Lapin, V. P., Shkolnikov, V. M. , and Shor, G. I., Laboratory methods

for investigation of additive oil detergency, Proc . First European Tribology Cong .

,

Inst. Mech. Engr., London, England (Sept. 25-27 1973). [29] Blagovidov, I. F. , Lapin, V. P., and Shor, G. I., Exploitation properties of fuels and oils, Phlenum Translation from Khimiyai Tekhnologiya Topi i

v

2 Masel , 16, [1], 37-41 (1971).

204
National Bureau of Standards Special Publication 584. Proceedings of Joint Conference

on Measurements and Standards for Recycled Oil/Systems Performance and Durability held at NBS, Gaithersburg, MD, October 23-26, 1979. (Issued Nov. 1980)

DEVELOPMENT OF THE ARMY THERMAL OXIDATION LUBE OIL TESTER

Mike Valtierra and Sidney J. Lestz

U.S. Army Fuels and Lubricants Research Laboratory Southwest Research Institute

San Antonio, TX

1. Introduction

The U.S. Army has a requirement to develop a bench-scale test capable of evaluating

candidate military specification engine and gear lubricants. Of major concern in lubricant performance is the amount of oil deposits that is formed on hot surfaces since excessive

deposits can drastically shorten the life of an engine. The Army currently has five speci- fications for their engine and gear oils, namely: MIL-L-2104C; MIL-L-46152; MIL-L-46167;

MIL-L-21260; and MIL-L-2105. However, it is believed that these specifications may fail to provide sufficient quality control for new oil batch-to-batch variations, whether of virgin

or re-refined origin. Also, quality conformance or quality assurance for new oils brings up the question, "Is our new oil buy on a current specification going to be as good as the

'original' qualified sample?" "What about re-refined oils?" An effective bench test can

help answer some of these questions and can assist in new lubricant development, particularly in the area of oil deposition.

2. Background

Historically, the evaluation of engine and gear lubricant performance in the areas of deposition, degradation, viscosity stability, and wear has relied primarily upon data gen- erated using single-cylinder and full-scale engine dynamometer and gear-train dynamometer

tests. These tests, including the single-cylinder engine tests, are expensive and time

consuming. In order to reduce dependence on costly engine tests and full-scale gear-train

tests, investigation of bench-scale performance tests similar to those used in MIL-L-7808,

MIL-L-23699, and MIL-L-17331 lubricant specifications is proposed for initial screening of engine and gear lubricants.

3. Objective

The objective of this work is to develop a bench-scale test capable of evaluating

ground vehicle engine and gear lubricant performance in the area of oil deposition. The

test should be capable of providing initial screening for candidate military specification

lubricants, oil base stocks, and re-refined oils and should correlate with full-scale engine

tests.

4. Test Development

In order to meet these goals, the Army Fuels and Lubricants Research Laboratory (AFLRL)

at Southwest Research Institute investigated the use of bench-scale performance tests similar to those used in Air Force and Navy MIL-L-7808, MIL-L-23699, and MIL-L-17331 lubricant

specifications. The study consisted of: 1) investigating current bench-scale tests; 2) selecting two promising tests; 3) generating limited test data using the two testers; and

4) selecting the most promising tester and generating additional data for correlations with

engine test stand data.

205
4.1. Current bench tests

A brief study was performed to investigate existing bench tests. The following tests were considered: 1) oxidation-corrosion tests, 2) WADD gear machine, 3) Cannon shear- stability test, 4) thermal oxidative test, 5) hot-wall deposition test, and 6) the AFLRL-modi f ied Alcor Test Fuel Thermal Oxidation Tester (JFTOT) test. The study indicated that the hot-wall deposition test and the AFLRL-modi f ied JFTOT (now called the "LUBTOT") test were the most promising.

4.2. Hot-wall deposition test device

The hot-wall deposition test rig was developed for the Air Force and is described in AFAPL-TR-72-25. This test rig utilizes a component of a jet engine on which oil deposits

are formed. A special resistance heater was designed and attached to the jet engine com- ponent to provide a heat source. Oil was sprayed onto the flat surface at a controlled

rate. A rating technique was developed to rate the oil deposits formed on the hot, flat

surface. Four lubricants (REO-185, -203, -204, and CCL-L-709) were evaluated using the hot-wall deposition test rig, and the results were compared to available Caterpillar 1-G test data. The deposition data obtained from the hot-wall deposition test rig ranked the four lubricants in the same relative order as the Caterpillar 1-G mean weighted total de- merit (WTD) ratings.

4.3. Alcor Jet Fuel Thermal Oxidation Tester

Figure 1 illustrates the unmodified Alcor Test Fuel Thermal Oxidation Tester. This de- vice is normally used for ASTM 0 3241 fuel tests, but was modified with an external recircu- lating oil system to study oil deposition. This tester is of interest because of several distinct advantages over the hot-wall deposition tester, namely: 1) ease of controlling

test variables, 2) small oil sample required, 3) ease of cleaning between tests, 4) sample unbias deposit rating method, and 5) lower cost per sample. The test section and fuel reservoir are shown on the right side of the illustration.

4.4. The LUBTOT tester

Figure 2 illustrates the LUBTOT oil -air flow system that was incorporated into the JFTOT. The tester consists of a stainless steel heater tube as the test section in which

deposits are formed. Heat energy is directed into the heater tube by the bus bars located

at each end of the tube. A control thermocouple is placed into the hollow heater tube. Oil and air are directed around the outside of the heater tube by a metering pump and flowmeter, respectively. The oil-air then passes from the heater tube housing and is returned to a vented reservoir. From the reservoir, the lubricant is directed to the metering pump and

the cycle is repeated. An oil-in preneater maintains the oil -in temperature at a controlled

value.

4.5. Test conditions

Table 1 illustrates the test conditions established for the LUBTOT. In this program,

it was decided to vary the heater tube temperature and hold the other variables constant.

A series of tests was performed at different heater tube temperatures ranging from 246 °C (475 °F) to 371 °C (700 °F) in order to establish a reasonable test temperature. An oil volume of 100 ml was selected, while the oil-in temperature was controlled to 93 °C (200 °F). The oil and air flowrates were set at 3 and 10 ml/rnin, respectively. A vented reservoir was

used, and a test time period of six hours was selected.

4.6. Test lubricants

The test lubricants selected for this work may be divided into three groups: 1) CRC Reference Engine Oils, 2) Army Military Specification Oils, and 3) formulated re-refined

oils. Correlation work was performed using CRC Reference oils: REO-185, REO-191, RE0-203, REO-204, and CCL-L-709. These oils were selected because of the available single-cylinder Caterpillar (CAT) reference test deposition data on Weighted Total Demerits (WTD) and Top

Ring Groove Fill (TGF). 206
Figure 1. Alcor Jet Fuel Thermal Oxidation tester.

207
CONTROL T/C ^ ^ POWER IN BUS BARS

HEATER TUBE HOUSINGXr

OIL-AIR IN T/C

AIR IN

AIR FLOWMETER

OIL PREHEATER

RESERVOIR

METERING PUMP - Y5TJ

\2T

Figure 2. The LUBTOT oil -air flow system. Table 1. Test conditions. Heater tube temperature

Oil volume, ml Oil -in temperature

Oil flow, ml/min

Oil sump pressure

Air flow rate, ml/min Test time, h

Variable

100

93 °C (200 °F)

3 Atmospheric

10

6 Other lubricants investigated included the following Army Military Specification Oils: MIL-L-2104C tactical/combat oil, single viscosity grade, OE/HDO MIL-L-2104C tactical/combat oil, candidate multiviscosity

MIL-L-46152 commercial/administrative oil MIL-L-46167 Arctic engine oil, OEA MIL-L-21260B preservati ve/break- i n oil

A few tests were also performed using different re-refined base stock oils and formulated re-refined oils conforming to the MIL-L-46152 specification.

208
4.7. Test procedure

Prior to starting a test, the 316 stainless steel heater tube is placed in a lathe, rotated, and polished for cleaning. The center section of the tube (where the deposits are formed) is cleaned by using metal polish (A-l metal polish, J. L. Prescott Company, Passaic,

NJ) with lint-free disposable tissues. After cleaning, the heater tube is placed in a calibrated Alcor Mark 8A Tube Deposit Rater (TDR) to obtain a clean tube rating. The tube rater subjects the heater tube to a light source of known intensity. Reflected

light from the heater tube is sensed and electronically measured and displayed by an indica- tor needle on a 0-50 scale, depending upon the intensity of the reflected light. A low reading indicates a low deposit level while a high reading indicates a high deposit level. A clean tube provides a TDR reading of 0. The clean rated heater tube is installed into the tester, and the reservoir is charged with 100 ml of test oil. The test is then performed under controlled test conditions for six hours. Upon completion of the test, the heater tube is removed, rinsed with trichloroethylene,

and placed in the Alcor Mark 8A TDR to obtain a reading of the dirty tube. As before, readings are taken at three locations on the tube (while the tube is spinning) and averaged to obtain the LUBT0T rating.

4.8. Typical deposits

Figure 3 illustrates typical deposits formed on the heater tube after a six-hour test. The two heater tubes at the top were tested with RE0-204 oil at 371 °C (700 °F). These

tests resulted in LUBT0T ratings of 40 and 46 for tests 4A and 2A, respectively. Other

tests performed under the same test conditions using RE0-185 resulted in LUBT0T ratings

of 31 and 32 for tests 3A and 1A, respectively. Compositional analysis of the deposits obtained in the LUBT0T was beyond the scope of this program, and only recently was the concept of weighing deposits introduced.

5. Discussion of Results

LUBT0T tests were performed under controlled test conditions at various temperature

levels in order to study oil deposition characteristics of various lubricants.

5.1. Effect of test temperature

Figure 4 illustrates the effect that test temperature has on various lubricants. This

figure represents the spread of the LUBT0T deposit ratings obtained for CRC Reference oils, MIL-L-2104C oils, and MIL-L-46167 oils subjected to 260 °C (500 °F), 316 °C (600 °F), and

371 °C (700 °F) temperature levels. As expected, when the heater tube test temperature was

increased, a corresponding increase was obtained in the LUBT0T deposit ratings. There was

some noticeable overlap in the LUBT0T deposits for the three temperature levels investigated.

This overlap can be attributed to normal test scatter, lubricant effectiveness, and lubricant

ineffectiveness under selected test conditions.

5.2. Effect of deposit buildup

A series of LUBT0T tests was performed using three reference engine oils to study the effect of deposit buildup. Figure 5 illustrates the results obtained with REO-204, RE0-191,

and REO-185 reference engine oils at 315 °C (600 °F). In these three groups of curves, the abscissa denotes the LUBT0T test time in hours with the ordinate denoting the LUBT0T deposit

rating. In each of the tests, the heater tube was removed every hour and rated, then the LUBT0T test resumed for up to six hours. The dark points at the six-hour time interval indi- cated other uninterrupted LUBT0T tests performed on the RE0 oils.

209
?. in
! 1— CRC REFERENCE OILS

MIL-L-2104C

MIL-L-46167

tf 50 - z

<

05 40 - H

O

u 30 - Q

I-O

5 20 -

10 -

0 I I i I 260°C 316°C 371°C 500

C F 600°F 700°F LUBTOT HEATER TUBE TEMPERATURE

Figure 4. Effect of test temperature.

The results obtained with the REO-185 high ash, series 3 oil buildup tests showed a very low increase in deposit buildup with time. Other tests performed with the REO-191

lubricant (a CRC Reference oil for MIL-L-2104B) resulted in a greater increase in deposit

buildup with time. Three additional tests performed with the CRC Reference lubricant

REO-204 (now an existing reference oil for MIL-L-2104C) resulted in an increase in buildup

of deposits, with the deposits leveling out after about three hours in the tester. Test repeatability appears to be reasonable for the lubricants evaluated, while discriminating

lubricant quality levels.

As noted earlier, the U.S. Army has a requirement for using various military specification lubricants for various vehicle applications. In order for these lubricants to be qualified under a specific military specification, they must pass one or more required

diesel engine tests. Table 2 lists the major Army ground vehicle lubricants. LUBTOT tests

were performed using these lubricants.

211
Table 2. Army oils and diesel engine test.

Qi Is Required diesel engine tests MIL-L-2104C CAT 1-D, 1-G2 MIL-L-2104C CAT 1-D, 1-G2, proposed 6V-53T (Proposed multivisc) MIL-L-46152

MIL-L-46167

MIL-L-21260B

CAT 1-H2 6V-53T Arctic procedure

CAT 1-D, CAT 1-G2

2 3 4 TEST TIME, HRS

Figure 5. Effect of deposit buildup.

As noted in table 2, the straight grade MIL-L-2104C, the proposed multi viscosity

MIL-L-2104, and the MIL-L-21260B specifications require (Caterpillar) CAT-ID and 1-G2 diesel engine tests. The proposed multiviscosity lubricant may also require a 240-hour 6V-53T diesel engine

test for lubricant qualification. The MIL-L-46152 administrative oil requires the CAT 1-H2 test while the MIL-L-46167 Arctic oil requires a 6V-53T test performed using the Arctic procedure. All of the required diesel engine tests are described by various Federal Test

Methods.

212
5.3. Correlation of LUBTOT tests and engine tests Single-cylinder Caterpillar reference test data were obtained for most of the lubri- cants used in the LUBTOT program. Single test deposit information for both top ring groove

fill and weighted total demerits were obtained from MERADCOM for 1-D, 1-G, 1-G2, 1-H, and 1-H2 Caterpillar tests performed on military specification oils. Also, single test re- sults performed at AFLRL on 6V-53T diesel engines were collected. Other engine test re- sults were also obtained for Caterpillar Reference Tests for REO and CCL oils. Of prime importance in any correlation made between test devices is test repeatability.

It is well known that the single-cylinder Caterpillar reference test performed on selected

REO and CCL lubricants results in considerable variance in test repeatability. Reference

ratings are usually tabulated and provide the number of tests performed, the mean rating, and the standard deviation calculated for the number of tests performed.

5.4. LUBTOT and CAT 1-G test results Duplicate LUBTOT tests performed using three REO oils resulted in a straight line cor- relation between LUBTOT results and Cat 1-G tests using the WTD mean ratings. In figure 6, the abscissa denotes the LUBTOT deposit rating with the ordinate denoting the Caterpillar

reference test Weighted Total Deposits. Duplicate LUBTOT tests were performed at 316 °C (600 °F). The test data for the REO oil tests are shown with the minimum and maximum val- ues of the CAT 1-G test data using the 80 percent confidence limit range. A reasonable

sample size ranging from 11 to 39 tests was available for all REO oil tests, thereby adding confidence to the reference test data and subsequent correlation. Duplicate LUBTOT tests resulted in good test repeatability. As noted by the dash line, a straight line correlation was obtained.

400

300

200

LUBTOT 316°C(600°F) CAT 1-G

11 TESTS39 TESTS. » /

/

/

/

/

/

/

/

- 18 TESTS

REO-204

REO-203

RE0-185

0 10 20 30 40 50 LUBTOT DEPOSIT RATING

6. Correlation between LUBTOT and Caterpillar 1-G tests. 213
Figure 7 illustrates the results obtained for four MIL-L-2104C lubricants evaluated at

316 °C (600 °F). The solid line represents the correlation curve obtained from figure 6 be- tween the CAT 1-G tests and the LUBTOT results. As noted in the lower right, "AL" code num- bers have been assigned to the commercial lubricants qualified under the MIL-L-2104C lubri- cant specification. In all cases, the single point test results fell below the correlation

curve.

LUBTOT DEPOSIT RATING

Figure 7. LUBTOT deposit ratings obtained on several MIL-L-2104C Army oils with corresponding Caterpillar qualification 1-G tests.

5.5. LUBTOT and CAT 1-G2 test results

Six LUBTOT tests were performed at 316 °C (600 °F) using REO-191, REO-204, and REO-203 reference oils. The results of these tests are plotted against the CAT 1-G2 WTD rating data and illustrated in figure 8. As presented earlier for the CAT 1-G tests, the minimum, mean, and maximum values of the weighted total demerits are shown for each of the oils. The dupli- cate LUBTOT tests performed resulted in good repeatability.

The LUBTOT results for the REO-191 and REO-203 lubricants correlate well with the Caterpillar reference test WTD ratings, while the LUBTOT results obtained for the REO-204

oil were too high.

214
530 400

£ 300

200

<

LUBTOT 316°C(600°F) / CAT 1-G2 /

/,

/

/

64 TESTS V

88 TESTS

/

/

/i

/

/

ofo

5 TESTS

/

REO-191

- REO-204

- RE0-203

0 10 20 30 40 50 LUBTOT DEPOSIT RATING

Figure 8. Correlation between LUBTOT and Caterpillar 1-G2 tests. Figure 9 illustrates the results obtained for four military specification lubricants

for which CAT 1-G2 test data were available. The solid line represents the average line for

the CAT 1-G2 engine tests performed on the REO oils. The LUBTOT data obtained did not sig- nificantly differentiate deposit values for the several lubricants evaluated.

5.6. LUBTOT and CAT 1-D, 1-H, and 1-H2 test results

Each of these reference tests had only two tests for comparison with LUBTOT test re- sults. Based on the limited available data, no correlation trends could be made with either

the "weighted total demerits" or the "top ring groove fill".

5.7. LUBTOT and 6V-53T test results AFLRL performs 100- and 240-hour 6V-53T diesel engine tests using selected Army lubricants. These tests are mainly wear tests and are not specifically designed as oil deposition

tests. However, ring groove carbon filling data are taken for both the 100- and the 240-hour

tests. Pistons are rated for deposits in the 240-hour test only.

215
LUBTOT DEPOSIT RATING

Figure 9. LUBTOT deposit ratings obtained on several Army oils with corresponding

Caterpillar qualification 1-G2 tests. An effort was made to study the piston deposits with corresponding LUBTOT tests. The results are presented in figure 10. In this figure, the weighted total deposit data ob- tained for each of the six pistons were added and averaged. This average WTD rating was plotted against the LUBTOT data for the three MIL-L-2104C lubricants evaluated. The plot resulted in a correlation for 316 °C (600 °F) LUBTOT tests performed. Other tests per- formed at 260 °C (500 °F) and 371 °C (700 °F) resulted in more scatter in the LUBTOT data.

5.8. Re-refined oil base stocks and formulated oils Of significant importance to the re- refiner is the capability to obtain a measure of consistency of base stock oils and to determine the effectiveness of formulated oils regarding oil deposition. Figure 11 illustrates the results obtained for various LUBTOT tests performed with re-refined oils. The clear bar charts represent the LUBTOT deposit data obtained for six different re-refined base stock oils. These LUBTOT tests resulted in high but different deposit levels for five of the six tests performed. These differences pro- vide a measure of the consistency of the base stock oils evaluated. Additional LUBTOT tests were performed using formulated oils (indicated by the dark

bar charts) blended in accordance with MIL-L-46152 using the same six different re-refined

oil base stocks, all with the same additive package. In five of the six cases, lower oil deposits were obtained, indicating the beneficial effect of the additive package as a re- sult of the low LUBTOT deposit ratings.

216
500

o

H

in>

KS

eM

400 -

316°C(600°F]

290

100

)°C[500°F) I y

y / y

11/

!/

371°C(700°F)

///

MIL-L-2104C

_l_ _L_

AL-6856

AL-6855 AL-7235

0 10 20 30 40 50 LUBTOT DEPOSIT RATING

Figure 10. Correlation between LUBTOT and 6V-53T engine tests.

H 40 -

BASE STOCK Z FORMULATED

DIRTY

igure 11. LUBTOT deposit ratings for re-refined base stock and formulated oils at 260 °C (500 °C). 217
5.9. Effect of base oil with feedstock

Tests were performed with the LUBTOT tester at a test temperature of 246 °C (475 °F) to determine if the tester could identify residual contaminants in a given re-refined base oil. Figure 12 illustrates the results obtained with the percent feedstock as the abscissa and the LUBTOT Deposit Rating as the ordinate. In these tests, the test oils were contaminated with

various percentages of drain oil feedstock.

10-

0 20 40 60 80 100 FEEDSTOCK, %

Figure 12. Effect of re-refined base oil contaminated with feedstock oil. The test results indicated that both an additive and a contamination effect were

present. Since very small quantities of feedstock were blended with the re-refined base

oil, the LUBTOT produced fewer and fewer deposits down to a value of 15. When more than

10 percent of feedstock was added to the re-refined base oil, the deposits increased

drastically. Duplicate LUBTOT tests performed with 100 percent feedstock resulted in LUBTOT ratings of 50 plus. Since the LUBTOT deposits were not in direct relationship with increasing amounts of feedstock, it was not possible to identify residual contaminants in the re- refined oil.

218
6. Conclusions

The following conclusions may be drawn from this work:

1) The AFLRL-developed LUBTOT appears to be an effective test device for evaluating lubricants regarding oil deposits that are formed under a set of controlled test conditions. The tester has several distinct

advantages, namely: ease of controlling test variables, small oil sample required, ease of cleaning between tests, simple unbias deposit

rating method, and low cost per test.

2) The test method developed thus far does correlate with some of the Caterpillar single-cylinder reference tests. However, the method does

not correlate with the 1-D, 1-H, and 1-H2 test results performed on selected REO oils.

3) The LUBTOT appears to be capable of differentiating between different

re-refined base stock, which can be important in identifying base stock consistency.

4) The LUBTOT can determine the effectiveness of the additive package in formulated oils regarding oil deposits caused by high-temperature

operation.

7. Recommendations

1) Further development is needed to increase the LUBTOT' s discriminating

sensitivity of the deposit results.

2) Additional development work is required to improve correlation of the LUBTOT results with the two main reference tests, namely the CAT 1-G2

and the CAT 1-H2 tests.

3) Additional LUBTOT tests should be performed on oils that have failed

the Caterpillar tests. This additional testing should aid in establishing a procedure fo»~ screening candidate lubricants, i.e., establishing

a pass-fail criteria.

4) Consideration should also be given to studying the effect of oil-air

residence time, oil volume, and greater air-to-oil ratios in an effort

to further oxidize the test lubricant.

5) Additional LUBTOT tests should be performed using virgin base oils for direct comparison with virgin base oils with additives and re-refined

base oils and re-refined oils with additives.

?iq

National Bureau of Standards Special Publication 584. Proceedings of Joint Conference

on Measurements and Standards for Recycled Oil /Systems Performance and Durability held at

NBS, Gaithersburg, MD, October 23-26, 1979. (Issued Nov. 1980)

PREDICTIVE TEST METHOD FOR COKING AND FOULING TENDENCY

OF USED LUBRICATING OIL

G. L. Steele, D. W. Brinkman, and M. L. Whisman

United States Department of Energy Bartlesville Energy Technology Center

Box 1398 Bartlesville, OK 74003

A short, reliable test has been developed to measure the coking and fouling tendency of used lubricating oils undergoing thermal stress. The technique utilizes commercially available instrumentation and requires only 200 mL of sample and three hours analysis time. Correlations based

on oils of known quality demonstrate good qualitative predictive abilities, while reproducibility studies demonstrated quantitative reliability. It

is shown that ash content alone may not always be a reliable measure of fouling potential.

1. Introduction

The aain reason for test method development in the petroleum field is to provide infor- mation that will improve processing efficiency. Heat transfer losses due to coking and fouling, and subsequent equipment downtime, can be extremely costly [3] 1

. Re-refining of used lubricating oil involves many processing techniques similar to those for virgin oil. However, contaminants found in used lubricating oil change its distillation characteristics, suggesting the need for a specific predictive fouling test for used crankcase oil. A pro- cess for re-refining used motor oil developed at the Bartlesville Energy Technology Center

(BETC), formerly the Bartlesville Energy Research Center (BERC), includes flash and vacuum distillation steps [8,9,10]. Fouling of heat exchangers is a potential problem, especially

in the early stages of processing an oil. Thus, a test designating the thermal stress characteristics of oil could save time and money. The oil re-refining industry uses weight percent ash [7,4] as an indirect measure of coking and fouling tendencies of oils. However, a more direct analysis technique is preferable, since unstable organic molecules degrade thermally and contribute to coking but are

not observed in ash analysis. Predictive methods described in the literature were developed for crude oil or finished

fuel processing systems. The more familiar are the ASTM-CRC Coker Test [1], a hot-wire test

[6], the Jet Fuel Thermal Oxidation Tester (JFT0T) [2], and the Erdco CFR coker [5]. These

tests require considerable quantities of sample or several hours of analysis time, or both, and probably are not directly applicable to re- refining problems. The method developed at BETC uses an apparatus with a flow-through cell containing a resistance-heated rod through the center. Except for reduced pressures, conditions within

the cell can be adjusted to simulate parameters in full-size heat exchangers. Temperatures

are maintained above those experienced in normal conditions in order to accelerate the ap- pearance of problems. The increased temperature also compensates for the difference in residence time between the test section and the heat exchanger. Oils of known character

have shown the technique to perform well, both qualitatively and quantitatively. Because

the method is based on constant flow for a fixed time period, it is adaptable to either on- stream or laboratory operations. Figures in brackets indicate the literature references at the end of this paper. 221
2. Experimental

2.1. Apparatus

The Alcor Thermal Fouling Testing (JFTOT-210), used in the test, is a modified Alcor

Jet Fuel Thermal Oxidation Tester. The Model 210 measures temperature change rather than pressure change as monitored by the latter unit. A 13 cm long, 5 mm i.d. test section was fitted with a 1015 carbon steel tube as shown in figure 1. The automatic temperature control was connected to the heater tube thermocouple, instead of the temperature monitor, to more closely simulate actual heat exchanger operation. The entire unit is automated so that

little operating time and attention is required.

Heater Tube

Nut

/ Fluid Out

O-Ring Seal

Thermocouple Assembly,

Fluid Out Temperature Thermocouple Assembly, Maximum Tube Temperature Housing Assembly for Heater Tube

3 —Fluid In Insulator Bushing

O-Ring Seal

Insulator Bushing

Figure 1. Heated test section.

2.2. Procedure

The feed pump is set so that oil passes over the resistance-heated steel tube at approx- imately 1 mL/min, providing a test section residence time of 100 s. The thermocouple

inside the heated tube is positioned 20 mm below the top of the heated section, normally,

the hottest spot. This thermocouple is wired to the automatic temperature controller. An- other thermocouple monitors the temperature of the oil leaving the test section. All test

runs are for 180 min under a nitrogen pressure of 400 psig. The nitrogen pressure pre- vents temperature fluctuation due to vaporization.

The tube temperature was constant at 750 °F, unless otherwise noted. Thus, oil-out temperature was directly proportional to heat transfer efficiency which decreased due to coke build up on the tube surface. The difference between the original oil-out temperature

at the start of the test and the final oil-out temperature was called delta T. After each run, the tube was cleaned of excess oil by submerging it in a graduated cylinder of heptane for two i '..u^s, wa^,,^.- with a stream of heptane, blown dry with air, and then weighed. The difference between this weight and that of the original tube is deposit weight. In addition to documenting changes in fluid temperature and deposit weight,

a visual inspection of the deposits were made, including a photograph for future reference. The tube was then prepared for a subsequent run by removing the coke with abrasive cloth,
smoothing with liquid metal polish, and rinsing with n-heptane. It is important to follow

the procedure exactly when mixing the sample, heating, cleaning, and weighing the tube. Deviations result in inconsistent data.

2.3. Sample preparation

Lubricating oils containing a range of contaminants were tested in this apparatus. These included commercial virgin-derived oils with additives, neat virgin-derived blending

stocks, and used oil at various stages of re-refining. For a determination of the quanti- tative nature of this technique, the following mixtures of an oil known to cause heat ex- changer fouling problems, (A), and a virgin-derived base stock, (B), were made: 1) 100 percent A; 2) 75 percent A, 25 percent B (by volume); 3) 50 percent A, 50 percent B; 4) 25 percent A, 75 percent B; 5) 100 percent B. Ash analysis (ASTM D 482) confirmed the accuracy

of these mixtures.

3. Results and Discussion

A standard requirement of any analytical method is the differentiation of qualitative

variations in known samples. Utilizing the five sample mixtures described in the experimental section, the method provided good qualitative discrimination at several temperatures

as shown in figure 2. A tube temperature of 750 °F provided maximum sensitivity while per- mitting even problem samples to complete the 180 minute test period without plugging of the test section. Premature termination of a test because of excessive coking limits the use- fulness of data obtained. By comparing the tubes from which curve 3 in figure 2 came, it can easily be seen that coke buildup increases with increasing temperature.

Figure 2. Gain in tube weight as a function

of heated tube temperature for five lubri- cating oil samples.

Tube Temperature, °F Quantitatve precision of the method was measured in two ways. First, five runs were

made with the same sample and the same tube. Then, 12 runs were made using four different

tubes three times each, as would be the more normal situation. The sample was number three

(50 percent A, 50 percent B) from the five standard mixtures. The change in fluid-out

temperature (delta T) showed instrumental short-term instability of up to 10 °F, making the statistical significance of temperature data questionable. This problem seemingly is not correctable. However, the relative standard deviation for coke weight was only 5.4 percent

for data from the same tube, and 9.5 percent for data from four different tubes. The im- plied difference in tubes can be partially attributed to thin areas from repeated cleaning, which become hot spots when used. The high cost of these special tubes discourages disposal after a single use. Tube weight variation was noted particularly when the oil coked significantly and the tube temperature was 750 °F or higher. Heavy deposits showed a tendency to flake, creating another source of inconsistency.

223
The weight of ash in a sample is commonly used as a measure of potential coking and fouling of an oil during thermal stress. Therefore, ash content and test results were com- pared for a wide variety of samples. The results are presented in figures 3 and 4, showing

coke weight versus ash, and change in fluid-out temperature (delta T) versus ash, respectively. All data were generated at a tube temperature of 750 °F. The scatter for the coke weight comparison is not nearly as large as for delta T. However, it is evident that ash content does not correlate well with Thermal Fouling Tester results. We attribute this lack

of correlation to unstable organic components which would not show up in an ash test.

Figure 3. Coke weight vs ash content at Figure 4. Delta T vs ash content at 750 °F. 750 °F. Another problem the user must be aware of is the varying heat transfer efficiencies of different coke deposits. For example, two tubes had deposits of about 0.025 g; yet the delta T for one was 110 °F, but only 6 °F for the other. On the other hand, two tubes re- flected a large difference in deposit weight, 0.017 g versus 0.993 g. Yet the delta T was

106 °F and 116 °F, respectively. Since the described method simulates actual conditions,

both deposit weight and changes in heat transfer efficiency can help predict potential

problems. Relying entirely on an indirect indication, such as ash content, may result in misleading assumptions. Relating test results to actual heat exchanger problems is much more difficult. For example, used oil having an ash content of 0.21 percent gave a delta T of 15 °F and a coke weight of 0.0406 g under the described test conditions. During a pilot-scale operation, a 4.5 square foot tube and shell heat exchanger, with a residence time of 10.5 min, lost significant heat transfer efficiency using the same oil. While the heat exchanger temperature was held at 730 °F, oil emerging from the heat exchanger dropped in temperature by

100 °F over a period of 72 h. A second batch of oil with a higher ash content of 0.53 percent yielded the same delta T of 15 °F and a lower coke weight of 0.0119 g on the Alcor

test apparatus. In the pilot-scale heat exchanger, a decrease in the emerging oil temperature of only 4 °F occurred after 80 h of continuous operation. This limited data implies that at least three factors must be considered in predicting coking and fouling of used

lube oil. The first is temperature, since used motor oils are sensitive to thermal stress, and coking problems generally appear when the oil is raised to about 500 °F. The second is the duration or residence time at elevated temperatures. A short time (s) at temperatures above 500 °F may prevent substantial coking especially if turbulent flow is maintained. And finally, ash must be considered as a contributing factor, although not necessarily a controlling factor in coke formation.

224
4. Conclusions

The described test provides reproducible results if one monitors coke weight deposited

on the heated tube. The method offers a relatively rapid and easy procedure for predicting

coking and fouling tendencies of a lube sample, with obvious parallel application to crude

oils and other similar materials. The automated instrumentation requires little operator

supervision. Future use in connection with pilot- and full-scale operations should provide

useful correlation data to help translate test results into predictable heat exchanger performance. References

[1] ASTM D 1660-72, Standard Test Method for Thermal Stability of Aviation Turbine Fuels.

[2] ASTM D 3241-77, Standard Test Method for Thermal Oxidation Stability of Aviation

Turbine Fuels (JFTOT Procedure).

[3] Braun, R. and Hausler, R. H. , Instrument measures fouling, helps plan, Oil and Gas

J. , 75, 90-100 (1977).

[4] Davidson, D. D. and Engesvik, B. I., Thermal treatment of used petroleum oils, U.S. Patent No. 4,033,859 (July 5, 1977).

[5] Frazier, A. W. , Huddle, J. G. , and Power, W. R. , New, fast approach to reduced preheat-exchanger fouling, Oil and Gas J., 63, 117-122 (1965).

[6] Hausler, R. H. , New test will show fouling, Oil and Gas J., 71, 56-63 (1973).

[7] Johnson, M. M. , Reclaiming used motor oil, U.S. Patent No. 3,930,988 (January 6, 1976).

[8] Whisman, M. L. , Reynolds, J. W. , Goetzinger, J. W. , and Cotton, F. 0., Process for preparing lubricating oil from used waste lubricating oil, U.S. Patent No. 4,073,719

(February 14, 1978).

[9] Whisman, M. L. , Goetzinger, J. W. , and Cotton, F. 0., Method of reclaiming waste

lubricating oils, U.S. Patent No. 4,073,720 (February 14, 1978).

[10] Whisman, M. L. , Reynolds, J. W. , Goetzinger, J. W. , Cotton, F. 0., and Brinkman, D. W. , Re-refining makes quality oils, Hydrocarbon Processing, 141-145 (1978).

225

National Bureau of Standards Special Publication 584. Proceedings of Joint Conference

on Measurements and Standards for Recycled Oil/Systems Performance and Durability held at

NBS, Gaithersburg, MD, October 23-26, 1979. (Issued Nov. 1980)

ANTIOXIDANT CONSUMPTION AND OXIDATIVE DEGRADATION

OF LUBRICANTS

Stefan Korcek, Lee R. Mahoney, Milton D. Johnson,

and Klaus Otto Engineering and Research Staff

Ford Motor Company

Dearborn, MI 48121

A general method for the determination of chain stopping anti- oxidants in new and used lubricants is described. The method is based

upon the titration of diluted lubricant samples with peroxy radicals. In contrast to standard determinations of viscosity, acid number, and insolubles,

the method provides information on lubricant oxidative degradation in the earliest periods of testing. Examples of the application of the method in various correlation and mechanistic studies of engine oil deterioration in spark ignited internal combustion engines are given.

1. Introduction Current engine oil formulations contain antioxidant additives which retard oxidative

degradation in the early periods of oil usage. When these antioxidant species are depleted, oxidative degradation of the oil occurs at an accelerated rate. Thus, information on the antioxidant concentration and its decay during use is an important indicator of lubricant

performance.

We have developed a method for the determination of the antioxidant capacity in new and

used oils. The method and its theoretical basis has been reported previously [l] 1

. This paper reviews the main features of the method and describes some of its most recent applications in various correlation and mechanistic studies of engine oil deterioration.

2. Method

The antioxidant species present in an oil sample are measured by titration with peroxy

radical

s

AH + nP^. inactive products

The titration is performed in the oxidation apparatus shown schematically in figure 1. A detailed description of the apparatus and procedure is given in the Appendix. Peroxy radicals for the titration are formed at a known and constant rate from the thermal decomposition of a free radical initiator, azobisiobutyronitrile, in a model hydro- carbon oxidation system containing cyclohexene as an oxidizing substrate and n-hexadecane as

a hydrocarbon solvent2

. In the absence of antioxidants the formation of peroxy radicals from

the initiator leads to rapid oxidation of cyclohexene. The resulting oxygen consumption is

figures in brackets indicate the literature references at the end of this paper.

2 Note, the model hydrocarbon oxidation system is used here not for evaluation of the oxidation stability of the lubricant, but only for the determination of antioxidants

in it. 227
monitored by recording the pressure change in the closed oxidation system If however

a small diluted sample of the oil (0.1-0.5 ml) is added into the system the oxidation of cvclohexene is suppressed until all antioxidant species present in the oi I are consumed by the reaction with peroxy radicals. The length of the time before the rapid oxidation of cyclohexene occurs, t, is directly proportional to the antioxidant capacity of the oil n(AH) 3 Typical peroxy radical titration curves for a new engine oil and used oil samples

from fleet testing of the same oil in a 5.0L engine are presented in figure 2.

LABORATORY TESTING

VEHICLE TESTING

o2 =60*0= =MODEL HYDRO!;arbon = EOXIDATION SYSTEM EE

DILUTED

OIL SAMPLE

OIL SAMPLE

2 ml HYDROCARBON

DILUENT REACTION CELL PRESSURE TRANSDUCER

jr i

CONSTANT TEMPERATURE BATH

Figure 1. Peroxy radical titration of antioxidants.

The peroxy titration method measures antioxidant additives which stop oxidation by reaction with peroxy radicals, i.e., chain stopping inhibitors, such as hindered phenols,

amines, and zinc dialkyl or diaryldithiophosphates. This method measures natural inhibitors" and antioxidant species generated in the lubricant during use but does not measure additives which stop oxidation by other mechanisms, such as peroxide decomposers and

metal deactivators.

»The antiox idant capacity of the oil is defined as a sum of the products of "tloxldant concentrations in the oil, (AH), and stoichiometric factors, n, given by the number of peroxy radicals terminated per molecule of a given antioxidant [2J.

228
ENGINE OIL FROM

FLEET TESTING

(5.0 L ENGINE) 0

" MILES

40 60 80 TIME , min 100 120

Figure 2. Peroxy radical titration curves.

3. Applications

The peroxy titration method has been successfully used for monitoring the decay of antioxidant capacity in engine oils during laboratory, Sequence IIIC, and fleet testing [2]. Results of these studies show clearly that the method provides important information on oxidative degradation in the early periods of testing when no other currently used per- formance characteristics show appreciable changes.

4. Engine Testing

A typical antioxidant decay curve for a synthetic hydrocarbon engine oil subjected to Sequence IIIC testing is given in figure 3. During such engine testing and service use periodic oil additions lead to periodic increases in the antioxidant capacity of the oil.

In the initial periods of engine testing or service use, while the antioxidant capacity

is still above its minimum effective level 4

, small changes in viscosity may be observed. These changes are due to evaporative loss of lighter engine oil components and to shear

down of VI improvers and other polymeric additives. Major changes in oil properties are observed only after antioxidant capacity drops below its minimum effective level.

'The critical level of antioxidant capacity at which an oxidative degradation of the oil begi

is designated as the minimum effective antioxidant capacity [2]. 229
Figure 3. Antioxidant decay during Sequence IIIC testing. The mileage at which the minimum effective antioxidant capacity is reached was found to depend not only on engine oil formulation and oil consumption but also on the size of engine

used [2]. Results from fleet testing showed that the rate of antioxidant decay in the initial periods of testing was in 2.3L engines about 20 percent lower than in 5.0L engines.

5. Mechanism of the Initial Antioxidant Decay Antioxidant decay data from various engines were found to be normalized when plotted

versus an "oil surface parameter" instead of mileage [3]. This parameter is defined as a product of the number of firing events and the surface area of the oil film per cyclinder.

The data from Sequence IIIC testing also fitted this correlation. This is particularly noteworthy since test conditions in the Sequence IIIC test are much more severe than those encountered in fleet service. The results of this correlation study suggest that the processes responsible for the antioxidant consumption in an engine are those occurring in the piston-cylinder area (fig. 4). There are numerous processes, however, which could account

for such consumption. They may include mechanochemical and thermal decomposition of zinc dithiophosphates and chemical interactions of fuel combustion products with the oil.

In order to isolate specific effects of combustion products on the decay of antioxidants, we utilized a reaction system in which the combustion products of isooctane generated by a pulse flame were transpired through a small sample of engine oil [3]. The

rate of antioxidant consumption was followed as a function of flame-oil distance and the concentrations of nitric oxide, carbon monoxide, and unburned hydrocarbons in the combustion

products. The results of these studies suggest that the main mechanism of antioxidant consumption in an engine involves interactions of the oil film with combustion-derived free radicals, other than nitric oxide.

230
NUMBER OF qilfilm Mn[AH])« ENGJNE X 8UR

°

F^

L?REA

Figure 4. Reactions of combustion derived free radicals with the oil film.

6. Implications of the Antioxidant Consumption Mechanism

The antioxidant consumption mechanism suggested previously implies that the initial antioxidant decay in an engine should be: 1) dependent on mode of combustion, 2) dependent

on type of fuel used, and 3) approximately independent of base oil composition. Implications

1 and 2 are currently being investigated in our laboratory.

The approximate independence of antioxidant decay in engines on base oil composition is supported by the results from an earlier study [2]. In that study, an oil thickening

characteristic in the Sequence IIIC test, the time to reach 400 percent viscosity increase,

was found to be approximately directly related to the initial antioxidant capacity of the

oil. All the oils having initial antioxidant capacity greater than 5.0 x 10 2 M, regardless

of oil formulation, passed the oil thickening requirement of the Sequence IIIC test. Six re-refined engine oils of different base oil quality were also analyzed (table 1). Their initial antioxidant capacities were in the range 4.9 - 5.6 x 10 2 M. All of these oils passed the oil thickening requirement of Sequence IIIC.

A further implication of this mechanism is that conventional laboratory oxidation tests

of engine oils may be qualitatively useful but will not show, in general, good correlation

231
with service. The reason for this has to do with the autocatalytic formation of free radicals in laboratory test methods. The autocatalysis will depend strongly on base stock composition. This behavior contrasts with the apparent constant flux of radicals from combustion in engine tests. Table 1. Sequence IIIC oil thickening and initial antioxidant capacity of

re- refined engine oils.

c pn TTTT Oil 10

2

l_n\.Hn; j Thickening*3 (M) ° Engine Base Oil Base Finished

Oil Quality3 SE SE

+ c Oil Oil

1 Good M M 1.0 5.6

2 Lesser M M 0. 9 5. 6

3 Good M F o'.s 5!2 4 Good M M 0.5 5.0

5 Excellent M M 0.6 5.4

6 Excellent M M 0.6 4.9

a Rating of base oil quality made by the ASTM Task Force on Re "rsfinsd Oils.

^F = failed to meet requirements.

M = met requirements.

c Defined as Av <400%. @64 hr. References

[1] Mahoney, L. R. , Korcek, S.

Hoffman, S. , and Wi 1 lermet, P. A. , Ind. Eng. Chem.

Prod. Res. Dev., 17, 250 (1978).

[2] Korcek, S. , Mahoney, L. R. , Johnson, M. D. , and Hoffman, S. , SAE Trans.

, 87, 3588 (1979).

[3] Mahoney, L. R. , Otto, K. , Korcek, S. , and Johnson, M. D. , Preprints, Div. Petrol. Chem., ACS, 24, [3], 802 (1979); Ind. Eng. Prod. Res. Dev., in press.

232
Appendix

DETERMINATION OF THE ANTIOXIDANT CAPACITY OF NEW AND USED LUBRICANTS: APPARATUS AND DETAILED PROCEDURE

Apparatus and Equipment . The apparatus, shown schematically in figure Al, consists of the following components.

1. Glass reaction cell consisting of a sample area (28 mm i.d. x 30 mm), 1, an inlet closeable with serum cap, 2, and a side arm connected to the measuring

system by a coupling (Cajon #SS-4-UT-l-2).

2. Measuring system constructed with coiled 1/8 in stainless steel tubing, 5, and handle,

6, which allows the reaction cell to be raised above the bath and removed for cleaning; a set of valves (Corning Stopcock #7500), S 7 - S 9 , and (Corning Stopcock

#7540), S 6 ; and a differential pressure transducer, 7, (Validyne Model DP15) range

± 1 psi , connected via transducer indicator (Validyne Model CD12), 8, to a strip chart recorder (Hewlett Packard Model 7100B), 9.

3. Vacuum and gas supply system which includes stopcocks S x - S 5 and S 10 , a reservoir,

10, mercury pressure relief valve, 11, mercury manometer, 12, and an outlet for a capillary pipet, 13, used for flushing the reaction cell.

4. Submersible magnetic stirrer (Troemner Model 700), 14, and stirrer controller, 15, for stirring the reactant mixture in the reaction cell.

5. Constant temperature bath, 16, with stirrer, 17, and temperature control system

(Lauda Model WB20D equipped with a duplex pump for external circulation and

Lauda R10 and R20 controllers), 18. Procedure

1. Flushing and filling the system with oxygen.

a. Close S x and S 9 ; open S 2 and S 4 , S 5 (close to relief valve), and S 6

- S 8

. b. Open S 3 and evacuate the system up to S 9 . c. Close S 3 , open S x and fill the system with oxygen. Keep the pressure in the oxygen supply line only slightly higher than atmospheric pressure. Open S 5 to the relief valve.

d. Open S 9 and flush the coil and cell with oxygen having the inlet, 2, open.

e. Open S 10 , flush and insert the capillary pipet, 13, through inlet 2 all the way to the bottom of the cell in order to flush the sample area, 1. f. Close S 6 and S 9 and maintain flushing through the capillary (close S1 , keep

S 10 open).

2. Charging the reactants to the cell.

a. Charge the required amounts of hexadecane, cyclohexene and sample into the

cell using syringes with long needles (20 cm); maintain oxygen flushing near

the top of the reaction cell.

b. Start magnetic stirring in the cell.

c. Remove the flushing capillary and quickly close the inlet, 2, with a serum cap.

d. Open S 9 , close S 7 and S 8 . e. Allow the temperature to equilibrate for about 15 minutes.

233
3. Adding the initiator.

a. Start the recorder (chart speed - 0.25 cm/mi n; full scale - IV).

b. Inject 0.5 ml of AIBN in chl orobenzene (0.2 M) through the serum cap using a 1 ml syringe with a long needle.

c. Open S 7 and S 8 momentarily to allow equilibration of pressure on both sides

of the transducer; reclose.

4. Measurement.

a. Open the measuring side of the transducer - open S 7 or S 8

. b. Record oxygen uptake, i.e., pressure decrease, versus time until the

final linear portion of the curve is sufficiently long to determine the final rate of oxygen uptake.

c. Open S 7 , stop recording, close S 9 ; discontinue stirring, lift up, disconnect

and clean the reaction cell.

d. Determine the inhibition time, t, graphically.

5. Typical Charge.

a. 9.0ml hexadecane.

b. 1. 0 ml cyclohexene.

c. 0.5 ml sample, diluted in hexadecane such that n(AH) is approximately

3.5 x 10 -3. This will give a final n(AH) in the cell of about 1.6 x lO"4 and an inhibition time of approximately 45 minutes.

d. 0.5 ml of AIBN in chl orobenzene (0.2M).

2 34


National Bureau of Standards Special Publication 584. Proceedings of Joint Conference

on Measurements and Standards for Recycled Oil /Systems Performance and Durability held at NBS , Gaithersburg, MD, October 23-26, 1979. (Issued Nov. 1980)

APPLICATION OF THE ANTIOXIDANT CAPACITY TEST TO RE-REFINED AND VIRGIN BASE STOCK OILS

R. E. Rebbert

Chemical Thermodynamics Division

National Bureau of Standards Washington, DC 20234

The antioxidant capacity test test developed by the Ford Motor Company

has been set up and is being examined for applicability to evaluate the relative free radical oxidation stability of various re-refined and virgin

base stock oils. This test will also be used in the ASTM/NBS base stock consistency study which wll begin in March 1980. The test method deter- mines the antioxidant capacity of a lube oil by measuring the length of

an induction period which preceeds the rapid uptake of oxygen by the test

solution. This paper describes the work to data on the antioxidant capacity test as applied to commercially available oils, reference oils, re- refined base stock oils and virgin base stock oils.

1. Introduction

In the past six months, as part of the recycled oil program here at the National Bureau

of Standards, we have used the method just described by Korcek et al. [1.2] 1 to determine

the antioxidant capacity of a number of different motor oils, including fully formulated commercially available oils, reference oils, unformulated re-refined base stock oils, and virgin base stock oils. Our purpose in using this method is to determine the antioxidant

capacity of various oils is two-fold. First, we intend to use this property of the oil, i.e., the antioxidant concentration, as one of a number of physical and chemical properties

that will be determined and tabulated for several re-refined and virgin base stock oils over

a period of 12 months as part of the ASTM/NBS Base Stock Consistency study that Dr. Frassa discussed earlier [3]. These results will give us some idea of the constancy or variability

of specific base oils from different refiners or re-refiners. We should also be able to investigate the additive response of each base stock oil. Secondly, by measuring the anti- oxidant capacity of various oils under a variety of conditions, we hope to develop a test procedure that will give, at least to some degree, an indication of the quality of the oil insofar as free radical oxidation stability is concerned. Both of these goals are relatively long term and this paper will be more of an initial progress report about the very preliminary work done so far.

2. Results: Antioxidant Capacity

In table 1 are shown the results of the measurement of antioxidant concentration for eight commercially available motor oils. All were labeled as multigrade SE quality and the first five are 10W-40 grade. These results are presented to show the range in antioxidant

concentrations that can be expected in the various commercial oils using this procedure. These data also provide an indication of our reproducibility which, depending on the concentration, and probably also on the nature of the antioxidant in the oil, varies from about 3 to 10 percent. Note that even for the five 10W-40 oils there is a 2 1/2 fold range in the apparent antioxidant concentration and a five-fold range when all eight oils are included. Table 2 lists the antioxidant capacities of what were originally thought to be ten reference oils as supplied by the Recycled Oil Program at NBS. It turned out to be five

pairs of reference oils. The agreement between the results for each pair again indicates

our reproducibility. In general, the agreement between duplicate oils is excellent, except

for the last pair which, although within the experimental error, shows a larger deviation

i Figures in brackets indicate the literature references at the end of this paper.

237
than the others. The correlation of the apparent antioxidant concentration with the results

of the III-C engine sequence test is only fair. In particular, the failure of the last reference oil 70P (No. 5292 or 5298) is somewhat surprising in view of the relatively high antioxidant capacity of this oil. There may be some significance to the fact that our reproducibility was also worst for this oil. If the particular antioxidant present in this

oil is not as effective in preventing oxidation as other antioxidants of similar concentration,

this may result in both the engine sequence failure and our i rreproducibi 1 ity. It may also

be a poor quality oil. Table 1. Antioxidant capacity of commercial oils. Measured Antioxidant Concentration

Oil (Moles/£) A(10W-40) .048 ± ,003 C(10W-40) .051 .002 D(10W-40) .020 .001 E(10W-40) .033 ± .002 H(10W-40) .035 ± .002 B(10W-30) .038 .004 G(10W-20) .029 ± ,003 F(5W-20) . 109 .003

Table 2. Antioxidant capacity of reference oils.

5295

5301 5291

5297

5293 5299 5294

5300

5292

5298

Measured Antioxidant Concentration

(Moles/£)

borderline fail

052 + .002 053 ± .005 034 + .002

035 ± .003 019 + .001 018 + .003 019 + .001 018 + .003 044 + .003 049 + .005

In a very real sense there is no reason to expect an exact correlation between the amount of antioxidant present in an oil and the quality of the oil. Although for a given

oil as the antioxidant capacity of the oil increases, the oxidation stability would be expected to increase, yet for different oils with the same concentration of antioxidant, the oxidation stability may be drastically different—depending on the quality of the base oil and also perhaps on the efficiency of the particular antioxidant used to inhibit the chain oxidation steps, or even the thermal stability or instability of the antioxidant itself.

In table 3 are the results for the determination of antioxidant capacity of unformulated re-refined base stock oils. As expected, there is very little antioxidant remaining in any

of these seven oils. In general, as it has previously been pointed out by Korcek and the Ford Group [4], the effectiveness of the antioxidant is drastically reduced when the concen- tration goes below a certain minimum value. This value is somewhat dependent on the type of

oil used and may also be dependent on the particular antioxidant used. For the values shown

here, very little residual antioxidant is expected in any of these oils. 238
Table 3. Antioxidant capacity of re-refined base oils. Measured Antioxidant Concentration

Oil No. (Moles/£)

5026 .012 ± .001 5027 .008 5028 .007 5029 .008 5030 .007 5031 .004 5032 .010

These results can now be compared with those given in table 4 where the antioxidant

concentration of some twelve virgin base stock oils are listed. As expected, these values

are even lower than those for the re-refined base stock oils. For these oils we appear to

be reaching the limit of the test procedure and as can be seen, the antioxidant concentration

is approaching zero. Table 5 briefly summarizes the results for all the different oils. Table 4. Antioxidant capacity of virgin base oils. Measured Antioxidant Concentration

Oil No. (Moles/je) 5037 .003 ± .001 5038 .004 5039 .004 5040 .003 5041 .004 5042 .003 5043 .001 5044 .001 5045 .001 5046 .002 5047 .003 5048 .002

Table 5. Summary of antioxidant concentrations.

Range Average

Commercial oils — ^FI SE Classification (8) .020 - .110 M .045 M ASTM IIIC Reference engine oils (5) .018 - .053 M .034 M Pass (2) 0.034 - 0.053 Borderline Foil (1) 0.018

Foil (2) 0.018 - 0.049 Re-refined base oils (7) .004 - .012 M .008 M Virgin base oils (12) .001 - .004 M .003 M

239
3. Results: Antioxidant Decay

As mentioned previously, the antioxidant capacity of an oil does not by itself give a measure of the relative oxidation stability of the oil. However, following in the footsteps

of the Ford group, it would seem that this method of determining the antioxidant capacity of the oil could be used along with an accelerated bench type oxidation test to determine the

rate of decay of the antioxidant in the oil. It is anticipated that this rate of decay of the antioxidant in the oil could be used, especially with unformulated re-refined and virgin

base stock oil, to determine the relative free radical oxidation stability of the various base oils.

If we assume, as a first approximation, that for each oil at a given temperature the concentration of free radicals in the oil (which eventually would react with oxygen and lead

to the oxidation of the oil) is essentially constant with time, i.e., a steady state assumption, then it is expected that the rate of decay of the antioxidant should follow a pseudo-first order rate law since the antioxidant in the oil is eventually depleted by reacting with these radicals. If this is true, then it means that a plot of the logarithm

of the antioxidant concentrations versus time should be a straight line whose slope should depend on the relative concentration of free radicals in the oil and consequently on the free radical oxidation stability of the oil. Thus, a good quality oil with a high free radical oxidation stability would be expected to give a decay curve with a shallow slope, while an oil with low free radical oxidation stability would be expected to give a steep decay curve. The experiments to check on the feasibility of this approach were just recently begun

and our results, at this time, are preliminary and few. In this work, we added an antioxidant, 2,6 di-t-butyl-4-methyl phenol to each oil so that the concentration of added antioxi- dant was 0.1 mol in each case (the total antioxidant capacity was 0.1 plus the original concentration). Then, 350 ml of this solution was placed in a 500 ml Erlenmeyer flask at a constant temperature of 150 °C with a fixed rate of stirring. Strips of copper, steel, and aluminum were added to each sample and at approximately 24 h intervals 10 ml portions were removed and the concentration of antioxidant determined. After about 120 hours the test was terminated. The results of this test for three of the reference oils and two re-refined

base stock oils are shown in figure 1. This is the antioxidant decay curve in which the logarithm of the antioxidant capacity is plotted as the ordinate versus time on the abscissa. For these five samples, straight lines are obtained over a period of three to four days in which about 80 percent of the antioxidants were used. After that time there is a considerable deviation from a linear plot. The slopes of these lines were determined and they are shown

in table 6. Table 6 Measured Antioxidant Capacity

Oil No. (Moles/£) R05295-71B .053 R05291-76A .035 R05293-70R .019 RB5027 .008 RB5026 .012

III-C Test

pass

pass borderline fail

Slope-, (hr"

1

) .0067 .0087

.0116 .0088

.0128

There are too few samples from which to draw any firm conclusions as yet, but at least

the slopes do appear to follow the IIC-C engine sequence test results for the three reference

oils. We hope to extend this work to more reference oils, re- refined oils, and virgin base oils in the near future.

The author expresses his sincere appreciation to Miss Enid Porrata Doria who conducted most of the experiments reported in this paper. This work was supported by the Recycled Oil Program at the National Bureau of Standards, Washington, DC. 24n
Fiaure 1 A plot of the logarithm of the antioxidant capacity, n[A], versus time for

the accelerated oxidation test. ®R0-5295 (71B), + RO-5291 (76A), QRO-5293 (70R), A RB-5026 and »RB-5027.

241
References

[1] Korcek, S. , Mahoney, L. R. , Johnson, M. D. , and Otto, K. , Antioxidant consumption and oxidative degradation of lubricants, Proc. Conf. on Measurements and Standards for Recycled Oil, NBS Special Publication 584, NBS (Gaithersburg, MD, Oct. 23, 1979).

[2] Mahoney, L. R. , Korcek, S. , Hoffman, S. , and Willermet, P. A., Determination of the antioxidant capacity of new and used lubricants; method and applications, Ind. Eng. Chem. , Product Research and Development 17, 250 (1978).

[3] Frassa, K. , ASTM/NBS Base Stock Consistency Study, Proc. Cong, on Measurements and Standards for Recycled Oil, NBS Special Publication 584, NBS (Gaithersburg, MD, 1980).

[4] Korcek, S. , Mahoney, L R. , Johnson, M. D. , and Hoffman, S. , Antioxidant decay in engine oils during laboratory tests and long drain internal service, International

Fuels and Lubricants Meeting, paper number 780955 (Toronto, Canada, Nov. 13, 1978).

24Z'
Session 6 BENCH TESTS FOR OIL EVALUATION

National Bureau of Standards Special Publication 584. Proceedings of Joint Conference

on Measurements and Standards for Recycled Oil /Systems Performance and Durability held at

NBS, Gaithersburg, MD, October 23-26, 1979. (Issued Nov. 1980)

PIN-AND-V-BLOCK AND RING-AND-BLOCK BENCH WEAR TESTS FOR ENGINE OIL EVALUATION

L. K. Ives and P. A. Boyer

National Bureau of Standards Washington, DC 20234

1. Introduction

As part of a National Bureau of Standards program to evaluate and develop methods to characterize re-refined lubricating oils, wear test procedures employing different specimen configurations are being studied. Two of these, the pin and V-block and the ring and block configurations are the subject of this investigation. A third configuration, the four ball,

is the topic of a companion article [l] 1

. Machines employing these configurations are among

the most widely used for general purpose lubricant evaluation. All are commercially

available and are designated in ASTM standard test methods. The principal focus of this investigation has been the evaluation of existing ASTM standard test methods. However, additional procedures were also examined. In this report, some aspects of the evaluation

method as well as test results will be presented.

The use of laboratory bench wear testing to evaluate the service performance of lubri- cants is often the source of considerable controversy. This is particularly the case for engine oils where the conditions are complex and the lubricant must serve a variety of func- tions in addition to controlling friction and wear. However, it is this complexity as well

as the prolonged nature and significant expense of service testing that makes laboratory wear

testing desirable. The need for rapid and relatively inexpensive bench tests becomes especially important with the prospect of small batch processing and potential source variations

that may accompany extensive recycling of lubricant products. Under these conditions, tests

to determine batch-to-batch consistency and the continued adequacy of a given additive package will become most important.

2. Evaluation Criteria

Three criteria were used in judging the value of a particular test procedure. They

were: 1) precision, 2) sensitivity, and 3) correlative capacity. Precision refers to the degree of agreement among repeated measurements of a given quantity. When the measurements

are made in a single laboratory by the same operator without a perceived change in conditions, the term repeatability is also used to describe precision. Most ASTM test methods for which round robin data have been obtained contain statements indicating the expected re- peatability. For example, D2670 [2] which utilizes the pin and V-block machine to measure

wear characteristics of fluid lubricants states that duplicate results are suspect if they differ by more than 22 percent of the mean value. Whether or not a satisfactory level of precision has been obtained may depend on the "sensitivity" of the test to the particular property being measured. For example, a test

that is highly repeatable but is insensitive to changes in the property being measured is of little value. While precision may be determined by comparing measured values obtained from a series of duplicate tests, sensitivity requires the application of the test to lubricants

having known incremental differences in the characteristic being measured.

1 Figures in brackets indicate the literature references at the end of this paper.

245
Table 1. Test oils

1. Paraffinic White Mineral Oil 335/350 SUS @ 378 °C

2. Re-refined Base Oil Viscosity Index = 90

3. Virgin Base Oil 600 second solvent extracted neutral Viscosity index = 94 Sequence IIIC Reference Oils: 70A - 64 h without excess viscosity increase

71B - Viscosity break-point = 40 h 70R - Viscosity break-point = 32 h 70H - Viscosity break-point = 16 h 70P - Viscosity break-point = 16 h

5. Sequence HID Reference Oils: 76A-1 - 64 h without excess viscosity increase _. Average cam and lifter wear = 19 ± 9 x 10 in (48 ± 23 x 10" 4 cm) from 17 tests) 77B-1 - Viscosity break-point = 24 h , Average cam and lifter wear = 113 ± 74 x 10 in (287 ± 188 x 10" 4 cm) from 22 tests Correlative capacity is used here to describe the extent to which test results correlate with service performance. Good correlation with service behavior is perhaps the most diffi- cult objective to achieve and demonstrate in a bench wear test. This is particularly true for engine oils where service performance depends on a variety of interdependent lubricant functions and a wide range of service conditions. In this investigation, IIIC reference oils and the more recently available HID reference oils, which will eventually supplant the IIIC oils, were employed to assess correlative capacity. The IIIC reference oils are designed primarily to determine high speed, high load oxidation resistance. Cam and lifter wear are measured as part of the sequence test procedure; however, the behavior of the IIIC oils does not vary greatly with respect to wear and the scatter in data is large. These oils are not designed to assess wear behavior. On the other hand, if oxidation or thermal degradation are experienced during the tests, an accompanying depletion of anti-wear additive may lead to severe wear. The wear test may then serve as a measure of thermal and oxidative stability. The HID sequence test procedure is similar to the IIIC procedure, but wear is a more impor- tant component of the test. Several HID reference oils are now available having signifi- cantly different wear characteristics. (The HID oils were not secured in time to play an important role in the present effort but will be used extensively in the future.) A measure

of the correlative capacity exhibited by a particular bench test procedure can, therefore, be obtained by comparing bench test results on a series of different reference oils with their

known performance. If the bench test procedure ranks the reference oils in their known order

of performance, then a high degree of correlation may be said to exist. This method also serves to calibrate the test procedure for application to oils of unknown behavior.

3. Test Oils

Oils to which the various test procedures were applied are listed in table 1. The virgin base and re-refined base stocks were selected on the basis of their in-house avail- ability and were not chosen to demonstrate a particular quality. A widely used and highly effective antioxidant - antiwear additive, zinc dial kyldithiophosphate (ZDDP) was mixed with

the base oils in concentrations ranging from 0.01 to 1.0 wt. percent to demonstrate the sensitivity of a given test procedure to a change in oil properties. Five IIIC and two HID

sequence test reference oils were employed mainly to examine the extent to which results from

a given test procedure could be correlated with oils having a known service performance, as

is described in the previous section.

246
4. Pin and V-Block Test Procedures

4. 1. Test machine

The pin and V-block test machine employed in this investigation was manufactured by the

Favi lle-LeVally Corporation. This machine which is often referred to as the Falex machine

(now designated the Falex #0 machine by its manufacturer) has been widely used for lubricated testing for approximately 50 years. Only a brief description of the machine will be given

since detailed descriptions are available in several ASTM standards including D2670 and D3233

[2] and in numerous articles, for example Crowley and Faville [3] and Faville and Faville

[4]. The test specimen configuration is shown in figure 1; two opposite V-blocks are squeezed against a rotating pin. Force is transmitted to the V-blocks through a lever arm system and is applied by a detachable load application assembly. This assembly contains a spring that is compressed against the lever arms by means of a threaded screw. Displacement

of the spring is indicated on a dial gage which is calibrated in force units. The load can

be applied manually or automatically by turning a ratchet wheel fixed to the threaded screw. Automatic advance is by means of an arm attached eccentrically to the specimen pin spindle.

As wear of the specimen occurs, the load decreases. The original load can be recovered by advancing the ratchet wheel. The number of ratchet teeth advanced provides a relative measure of the amount of wear during the test. The entire loading assembly and jaws holding

the V-blocks is free to rotate about the axis of the pin spindle but is held in place by a load cell. The latter gives an indication of the friction force. The standard machine is equipped for a single speed of operation, 290 rpm, and has provisions for heating the oil sample.

Several modifications were made in the machine during the course of this investigation. These modifications did not impair or alter the basic function of the machine but were intro- duced to provide better control and to facilitate the monitoring of test conditions. The modifications included adapting a strain gage load cell to the load application mechanism to permit electronic recording of the applied load, and replacement of hydraulic load cell and recording system that was supplied for indicating friction torque which was found to be insensitive and subject to severe thermal drift by a strain gage load cell system. Finally,

the simple oil bath heater control was replaced by a temperature controller with thermocouple

temperature sensing. During elevated temperature operation, heat is supplied both by the built-in heater adjusted to provide a set temperature at the beginning of the test and by friction. Without a temperature sensing controller, the temperature of the oil will rise as

a result of the frictional component. This may still happen under some test conditions even

with the temperature controller if the heat supplied by friction is greater than that dissi- pated to the surroundings. Under these circumstances, to maintain a constant temperature, it would be necessary to cool the oil bath.

V BLOCKS

Figure 1. Pin and V-block spec men configuration.

247
Temperatures at the specimen contact regions were in general higher than the oil bath temperature. One method [5] for obtaining a measure of the contact temperature is by means

of a thermocouple clamped at the bottom of the V-groove in one V-block. In this investigation, chromel-alumel thermocouple wires were spot welded to one V-block as illustrated in figure 1 in order to obtain a relative measure of the temperature in the contact region. With the pin and V-block machine equipped as described previously, it was possible to obtain a simultaneous recording of applied load, friction force, and temperature.

4.2. Applied load Three different kinds of load gage assembly are currently available for the Falex #0 machine. They are referred to as the 800 lbf (3550N), 3000 lbf (13300N) and the 4500 Ibf (20000N) gages according to the maximum indicated load value. The 800 lbf and 3000 lbf gages are designed to cover two different ranges of applied load but are otherwise essen- tially similar. The 4500 lbf gage, however, does not represent a further extension to a higher load range but is calibrated on an entirely different scale. The 800 lbf and 3000 lbf gages, sometimes referred to as direct reading gages, indicate the force applied directly to the V-blocks. This force corresponds to the test load L shown in figure 2. The 4500 lbf gage was originally designed to indicate the normal force at the pin and V-block contact junction (N in fig. 2). A change in V-block angle from 90° to the currently used 96°, together with other modifications, has altered this relationship making the direct gage rending invalid.

Figure 2. Diagram showing resolution of forces at pin and V-block contact junctions.

All gages are subject to calibration according to a procedure outlined in the various ASTM Standards (D2670, D3233, D2625) employing the Falex #0 machine. The procedure consists

of replacing the pin and V-block test specimens with a 10 mm Brinell ball and copper coupon

of hardness 37-39 BHN. On application of a load an impression is made in the copper coupon.

It is assumed that the Meyer law [6] is obeyed. The Meyer law is an empirical relationship which states that the load is proportional to the impression diameter raised to a constant

248
power and would therefore yield a straight line on a logarithmic plot. Such a graph of log "true" load vs log impression diameter for copper test coupons of the prescribed hardness is part of the relevant ASTM Standards (D2670, D3233, and D2625). The accuracy of the methods

depends on how well the response of the copper calibration coupon agrees with the graph published by ASTM. No recommendations are made for calibrating the test coupon itself--a

step which should be taken to be assured of an accurate determination of load using this

method.The 4500 lbf gage is calibrated on a scale that is related arbitrarily to the test load

L on the V-blocks. This relationship is also plotted on the true load vs impression diameter

graph published by ASTM. It should be noted that the load indicated by the 4500 lbf gage is not linearly related to the true load L. The 4500 lbf gage was not used here and all loads specified correspond to L indicated in figure 2. According to the force diagram shown in figure 2, the normal force N at each contact is equal to L/(2 cos 42°). Mecklenburg [7] has shown, however, that when frictional forces are included in the analysis the normal force on the incoming face of each V-block is larger than

that on the outgoing face. Depending on the friction force, the difference may be 30 percent

or larger. For this reason, considerable caution must be exercised in attempting to develop quantitative relationships to describe lubricant performance with the pin and V-block configuration.

4.3. Test specimens

The pin and V-block test specimens were obtained from Favi lle-LeVal ly Corp. and were manufactured to meet specifications given in ASTM standards D2670 and D3233. These specifi- cations require that the V-blocks be of AISI C-1137 steel with a hardness of HRC 20 to 24, that the surface roughness be 0.13 to 0.25 urn rms, and that the V-angle be 96° ± 1°. The

pins are to be of AISI 3315 steel with a hardness of HRB 87-91 and surface roughness of 0.13

to 0.25 urn rms. With the exception of the V-block angle, no tolerances are given on specimen

dimensions. Thus, the degree of flatness of V-block faces was found to vary considerably and this led to the formation of uneven wear scars. Another factor that had a significant effect

on test behavior was the method of finishing the V-block faces. V-blocks that were prepared

by surface grinding gave results that differed from those that were obtained from blocks produced by a coining operation. Only coined blocks were used here. Finally, variations in microstructure among different V-blocks were found to be the most

likely and perhaps serious source of data scatter. The V-blocks, it was discovered, had two rather different microstructures . Some had a ferritic-pearl itic structure typical of annealed medium carbon steel while others had a spheroidized structure apparently arising

from a different heat treatment. The hardnesses did not differ. Since these two block microstructures were found to yield considerably different results, care was taken, insofar

as was possible, not to mix the different microstructures in a given test series.

5. Pin and V-Block Procedures and Results There are two ASTM standard methods applicable to fluid lubricants that employ the Falex

#0 machine. They are: 1) D2670 Standard Method for Measuring Wear Properties of Fluid Lubricants (Falex Method), and 2) D3233 Standard Methods for Measurement of Extreme Pressure

Properties of Fluid Lubricants (Falex Methods). These two tests are, in general, characteristic of tests that are designed to measure the wear rate and load carrying capacity charac- teristics of lubricants, respectively. In the following discussion, results obtained using

D2670 will be considered first, together with some alternative procedures for determining

wear rate behavior of lubricants. D3233 and other tests for measuring load carrying capacity

will then be examined.

5.1. D2670 and wear rate measurement methods

Briefly, the procedure specified in D2670 consists of a run-in at 250 lbf (1100N) for 5 minutes followed by a 15 minute test at 700 lbf (3100N). The number of teeth by which the ratchet wheel must be advanced to maintain the load at 700 lbf (3100N) is taken as a measure

of the amount of wear occurring during the test. The specified initial oil temperature is 24 ± 3 °C with no requirement that it be maintained at that value during the test. As a result of frictional heating, the oil temperature may increase during the test. 249
Typical test results obtained with several different oils are shown in table 2. Each entry represents the average of 5 repeat tests. The first two oils, mineral oil with 0.1 w/o sulfur and mineral oil with 0.2 w/o sulfur, are calibration oils specified by D2670. The amount of wear, 60 ± 5 teeth and 107 ± 6 teeth, respectively, falls well within the range specified by D2670 for these oils. When the test procedure was applied to mineral oil without additives (see table 1) seizure occurred during the run-in period at 250 lbf (1100N)

load. Similarly, when applied to two IIIC reference oils seizure occurred during the test period at 700 lbf (3100N), well before 15 minutes was reached. Prior to seizure, there was relatively little wear. Table 2. ASTM D2670 test results.

Oil Mineral Oil +0.1% Sulfur

Mineral Oil + 0.2% Sulfur

Mineral Oil IIIC Sequence Test Oil - 70A (Pass) IIIC Sequence Test Oil - 70H (Fail)

Teeth Wear

60 ± 5 teeth (± 8%) 107 ± 6 teeth (± 5%) Seizure during run-in @ 250 lbf (1100N) Seizure during test @ 700 lbf (3100N) Seizure during test @ 700 lbf (3100N)

The procedure specified in D2670 is clearly too severe, not only for unformulated base stocks but also for fully formulated SE grade engine oils. D2670 is apparently better suited

for lubricants having relatively high entreme pressure characteristics such as cutting oils.

A number of tests were conducted at much lower loads and for longer periods of time than those specified in D2670. It was found that the load had to be reduced to as low as 50 lbf (220N) before long term (several hours) tests could be conducted on mineral oil without the occurrence of seizure. Repeatability for these tests was relatively poor. A test procedure that has gained some support among users of the Falex #0 machine is one that involves measurement of wear at a series of increasing load increments. Thus a characteristic curve relating wear to load is obtained. When a sufficiently high load is reached, seizure may occur so that, in addition, this method may also provide a measure of the load carrying capacity of the lubricant. Several variants of the procedure have been described [3,4,8]. Because the Falex #0 machine provides for measurement of wear during operation, the wear rate vs load curve, in principle, may be developed in a single test run without changing specimens. A disadvantage of this approach is the fact that at each successive load the specimens have been worn at the preceding levels. It has been suggested

that this method may be employed with relatively short time periods at each load to obtain a rapid estimate of behavior [8]. A sounder method consists of using a new set of specimens at each load level [4,8]. The latter procedure was applied to two IIIC reference oils and two HID reference oils. The results are shown in figure 3a and b, respectively. For these

tests, the initial oil temperature was 60 °C. A 5 minute run-in period at 50 lbf (220N) was followed by automatic advance of the load to the desired test level. The load was maintained

for 30 minutes at each level before terminating that test increment and determining the amount of wear. Wear was measured in terms of the mass lost from the pin. The teeth wear measurement method was not suitable because of the very small loss experienced during these

tests. Wear of the harder V-block was much less than from the pin but varied in about the same way. The wear behavior of the two IIIC reference oils shown in figure 3a is essentially

identical according to this test procedure. Wear at 300 lbf (1330N) and below is relatively

low. A sharp increase, by nearly an order of magnitude, is observed at 400 lbf (1800N). Seizure occurred within the first few minutes at a load of 500 lbf (2200 N). In contrast, the two HID reference oils which exhibit considerably different cam and lifter wear behavior (table 1) also differ according to this test as shown in figure 3b. Reference oil 77B-1 gives a relatively low wear rate at loads of 100 lbf (440N) and 200 lbf (890N), accelerates at 300 lbf (1800N) and fails at 400 lbf (1800N). A somewhat higher wear rate is obtained with reference oil 76A-1 at low loads. A drop is observed at 400 lbf (1800N) followed by an accelerating wear rate until failure occurred at 600 lbf (2700N). Failure for both HID oils was associated wth severe galling of the test specimens. If, in fact, resistance to galling is the critical factor in preventing cam and lifter wear, then

the test results in this example can be said to exhibit good correlation.

250
Pin and

Pin Wear

-Block

x IEC Refer O HIC Refer.s Oil 70A (Poss)

800

200

12 Pin ond V- Block Wear Test Results

10 f

8 A IHD Reference Oil 77B-I O m D Reference Oil 76A-I | 6

4

2 4

i i i

300

1600 2000 N

I I 400 500 Ibf

800

I 200 300 400

Test Load

1600 2000 2400 N

I I I 500 600

Figure 3. Pin wear as a function of load. Procedure consisted of a 5 min run-in at

50 lbs followed by 30 min at the test load, a) IIIC reference oils, b) HID

reference oils.

5.2. ASTM D3233 and other load carrying capacity methods Standard test method D3233 describes two methods for determining the load carrying

capacity of a lubricant. In Method A, following a run-in period of five minutes at 263 lbf (1170N), the load is advanced automatically until failure occurs or the maximum capacity of the machine is reached. Method B employs the same run-in step but the load is increased in increments and held one minute at each increment, first at 412 lbf (1830N) and then 589,

759, 924, 1085 lbf, (2620, 3380, 4110, 4830N) etc., until failure occurs. (With the 4500 lbf load gage, run-in takes place at an indicated 300 lbf (1300N) and the load is advanced to 500 lbf (2200N) followed by equal increments of 250 lbf (1100N). As pointed out earlier,

these equal increments of gage indicated load do not represent equal increments of force applied to the V-blocks.) The starting lubricant temperature for both methods is 51.7 ± 3 °C. Failure is caused by excessive friction which results in fracture of the pin or of the shear pin. Severe adhesive wear, galling or seizure at the specimen

wear zone are observed. Extrusion of the pin without macroscopic evidence of severe adhesive wear occurs with some lubricants having high load carrying capacities.

Examples of galled and extruded pins are shown in figure 4. The rather high run-in load of 263 lbf (1170N) renders the application of D3233 to base

oils and engine oils having load carrying capacities lower then SE grade oils of marginal

value. In order to extend D3233, Method A to lubricants ranging from mineral oil without

additives to fully formulated SE grade engine oils, a procedure employing a run-in at 50 lbf (220N) followed by automatic advance of load to failure was investigated. The run-in step included 2 hours with mineral oil followed by 1/2 hour with the oil to be tested. This

run-in step produced a small amount of wear and generally led to full contact with the pin

across the slightly non-flat V-block faces. The initial oil temperature for this test was

251
60 °C. Figure 5 shows a typical simultaneous recording of V-block temperature, applied

load and friction force obtained during the automatic load advance portion of the test. The steady state temperature of the V-block at 50 lbf (220N) is higher than the bulk

oil temperature due to frictional heating. The increase in friction force with load is approximately linear until just prior to failure when a rapid rise in friction force

occurs. The point at which this sharp departure from linearity occurs is taken as the failure load. Good agreement is obtained between the failure load determined from chart recordings and visual observation of the load gage.

Figure 4. a) Pin that has failed due to galling and seizure, b) Pin that was extruded without evidence of severe adhesive wear.

Figure 5. Typical chart traces of friction force and temperature during automatic

load advance portion of load carrying capacity test. Results obtained by applying this procedure to three different base oils with 0 to 1.0 w/o ZDDP are shown in figure 6. Each point is the average of five repeat tests. Error bars represent the ± la limits. The response of the three base oils to the addition of ZDDP varies considerably. Mineral oil enhibits the most marked response. The load at seizure is multi- plied three times by increasing the concentration of ZDDP from 0 to 0.03 w/o. At concen- trations greater than 0.07 w/o, the pins were extruded without seizure. The response of the

25?
virgin base and re-refined base oils is not as great. When 0.05 w/o ZDDP is added to the virgin base oil, the seizure load is nearly doubled while there is only a slight increase for the re-refined base oil at this concentration. Increasing the concentration of ZDDP from

0.05 w/o to 1.0 w/o led to almost no change in seizure load for the virgin base and re- refined base oils, within the observed scatter. The latter observation suggests a saturation condition at concentrations of ZDDP higher than 0.05 percent.

Figure 6. Load carrying capacity test results for three base oils with concentrations

of ZDDP ranging from 0 to 1.0 w/o. Each point represents the average of five or more

replicate tests. Error bars give the standard deviations. The seizure test was also applied to five IIIC reference oils. The results are shown in figure 7. As might be expected, there is relatively little difference in their response to this test. The IIIC oils are optimized for the purpose of evaluating high speed, high load

thermal degradation behavior. Finally, it should be noted that the seizure test procedures were found to be especially

sensitive to metallurgical factors. V-blocks with an annealed pearl ite-ferrite structure

were found to exhibit seizure loads that were sometimes as much as 50 percent less than those

obtained with V-blocks having a spheroidized structure.

6. Ring and Block Test Procedures

6. 1. Test machines

The ring and block specimen configuration is shown in figure 8. The contact geometry is that of a cylinder on flat as was the pin and V-block configuration; however, the complicated

load distribution that arose as a result of multiple contacts is avoided here. There are

several different machine designs utilizing the ring and block configuration. Among the most widely used are the Timken and Alpha Model LFW-1 machines. Descriptions of these machines

can be found in [9] and in the ASTM standard methods which are referred to below. Both machines employ dead weight loading through a lever system but differ in design detail. The block is positioned above the ring as in figure 8 for the Alpha Model LFW-1 machine, while it

is below the ring in the Timken machine. In normal operation of the Timken machine, the lubricant is supplied through a nozzle to the ring and recirculated. With the Alpha Model LFW-1 machine, the ring is dipped into a reservoir of oil. A major difference between the

two machines concerns the size of the specimens used. The Timken design utilizes a ring having an outside diameter of 49.22 mm and width of 13.06 mm. The block is wider (19.05 mm) than the ring. The Alpha Model LFW-1 ring is 35.00 mm in diameter and 8.15 mm wide, while

the block is 6.35 mm wide and therefore narrower than the ring. The Favi 1 le-LeVal ly Corp.

has recently redesigned the Alpha Model LFW-1 machine and renamed it the Falex #1 machine. The Falex #1 machine was used in this investigation. Optional components are available to permit the Falex #1 machine to accept the Timken specimens and carry out tests designed for the Timken machine.

253
Ibf N 1400-

900 - 4000 -

and V- Block Seizure Test mc Reference Oils

8 16 24 32 40 48 56 64

IttC Sequence Test Viscosity Break- point Time (h) Figure 7. Load carrying capacity test results for five IIIC reference oils. Each point represents the average of five replicate tests. Error bars give the stan- dard deviations.

Figure 8. Block-on-ring test specimen

configuration.

6.2. Test specimens

The test specimens employed were those that meet specifications given in ASTM D2714

(Alpha Model LFW-1 size) and D2782 (Timken design).

6.3. Test procedures

There are two ASTM standard test methods applicable to fluid lubricants that employ the ring and block configuration. They are: D2714 Calibration and Operation of the Alpha Model LFW-1 Friction and Wear Testing Machine and D2782 Measurement of Extreme-Pressure Properties

of Lubricating Fluids (Timken Method). The evaluation of D2714 will be discussed below. 254
Evaluation of D2782 has not yet been undertaken, however a modification of this method has been examined. The modified method is one that has been employed by the Suntech Corp. [10] for the evaluation of engine oils and some preliminary results will be presented.

6.4. ASTM D2714

The scope statement accompanying D2714 indicates that the method provides a procedure

for calibrating and operating the Alpha Model LFW-1 machine (or the Falex #1 machine with appropriate adjustments to accommodate the slightly different design). No guidelines are given concerning the properties of the lubricant for which the method is applicable. The

test procedure is limited to a single set of operating conditions: 72 rpm, 150 lbf (3300N)

load, 43 °C oil temperature, 4500 revolutions. Calibration is established by applying the method to white mineral oil having a viscosity of 63 to 65cSt at 37.8 °C. The machine is judged to be calibrated if the block wear scar width falls between 1.70 and 2.90 mm with a repeatability range of 0.73 mm, and the friction force after 4500 revolutions is 66.7 to

87. 8N with a repeatability of 29. 3N. Figure 9 gives results obtained by applying the test procedure to mineral oil, the virgin base oil and the re-refined base oil all with con- centrations of ZDDP ranging from 0 to 1.0 w/o. In a single departure from ASTM D2714, the

oil temperature was maintained at 60 °C rather than the prescribed 43.3 °C. Each point in figure 9 represents the average wear scar width for at least five repeat tests. Error bars

give the ± la limits. The percent standard deviation is somewhat less for oils without ZDDP

(± 6 to ± 8 percent) than for oils with ZDDP (± 9 percent to ± 19 percent). Although there

is a significant difference in wear among the oils without ZDDP, that difference is essentially eliminated with the addition of 0.05 w/o ZDDP. In fact, within the observed

scatter, there is little difference in wear behavior for all oils with ZDDP. Since the amount of wear is brought to about the same level in all cases by concentrations of ZDDP

equal to or greater than 0.05 w/o, it appears that the presence of the additive dominates the wear process. In effect, the test does not discriminate between these oils at concentrations

of ZDDP > 0.05 w/o.

6.5. Suntech modification of D2782 ASTM D2782 is designed to determine the load carrying capacity of fluid lubricants. The measured quantities are the minimum load at which scoring or seizure occurs, maximum load (OK value that can be applied without scoring or seizure) and the pressure at the maximum load. The pressure determination is based on the measured size of the wear scar. The amount of wear is not one of the quantities designated for determination, however, this quantity is implicitly contained in the pressure measurement. Although seizure and scoring may be evidenced by noise and vibration during the test, a final determination is made by visual examination of the wear scar on the test block without the aid of a microscope. The test conditions prescribed by D2782 are summarized in table 3. Although ASTM D2782 has not yet

been evaluated in this program, a modification referred to as the Suntech Timken test has been examined. F. E. Didot of the Suntech Corp. reports good correlation with this test and

I I IC sequence test results. The Suntech Timken procedure is outlined in table 3 for comparison to D2782. The principal difference between the two methods concerns the quantity of oil that is supplied to the test pieces. A continuous flow of oil (rate not specified) is supplied in the case of D2782 while for the Suntech method the test pieces

are only wet with a film of oil at the start of the tests. Excess oil is thrown off during

the test. Since a supply of oil is not available for cooling, frictional heating may cause

a significant rise in temperature. This, in turn, may lead to an accelerated decomposition

of the oil as was evidenced during tests by the generation of smoke and appearance of deposits on the test pieces. Results obtained by applying the Suntech method to five I I IC reference oils, two HID

reference oils and two unformulated oils are given in table 4. The values listed were ob- tained through application of a single series of tests to each oil. That is, loads were

applied in increasing increments of 20 lbf (89N) for each trial until failure occurred (or decrements if failure was obtained in the first trial). In order to narrow the limits, increments of 5 or 10 lbf (22 or 44N) were then used. Replicate tests have not yet been run

to determine repeatability. Both friction force and block temperature were recorded simultaneously for each trial. A relative measure of block temperature was obtained by means

of chrome! -al umel thermocouple wires spot welded at a point about 1 mm distant from the

255
contact junction. Although failure was determined by examination of the block wear scar, it was also indicated by the friction force trace. Examples of friction force and block temperature traces for three tests are shown in figure 10. Figure 10a shows a typical example where failure did not occur. The friction force trace exhibits a sharp but brief

initial peak on application of the load and remains nearly constant thereafter. The block temperature rises continuously during the test. The load was increased by 10 lbf (44N) in figure 10b. The behavior was similar to figure 10a until near the end of the test when sharp fluxuations in the friction force indicated the onset of seizure. Failure also occurred in the example shown in figure 10c. With this oil, however, rapid wear was experienced on initial application of the 80 lbf (360N) test load; this is indicated by the broad peak in the friction force trace. A corresponding peak also occurs in the block temperature trace.

As a result of the rapid initial wear, the junction area is increased and the contact stress

is reduced. The remainder of the test was then completed without further evidence of failure. These results suggest that failure occurred in figure 10b because of thermal degradation effects while in figure 10c the load carrying capacity was exceeded initially.

RING and BLOCK ASTM D27I4 Standard Method at 60°C -4

i Contoct Width at 150 lbf ((

O Paraffin Oil A Virgin Base

Rerefined Base 05 0.6 ZDDP (Wt %) Figure 9. Results obtained by applying D2714 to three base oils with concentrations

of ZDDP ranging from 0 to 1.0 w/o.

Table 3. Summary of conditions and procedure for ASTM D2782

and Suntech modification. ASTM D2782 Suntech Quantity of oil

Oil temperature

Break- in Load increments

Time per increment

Speed

Continuous supply

100 ± 5 °F (37.8 ± 2.7 °C) 30s @ 1.5 lbf (67N) 100 lbf (440N) @ > 300 lbf (1300N)

60 lbf (270N) @ < 300 lbf (1300N)

10 min

800 rpm

Wet with oi

1

Room temperature

(Same)

2 lbf (89N)

5 min

(Same)

256
Table 4. Results obtained with Suntech modifications of ASTN D2782. Test Oil Max Pass Load Min. Fail Load

*R0 70A 64h pass 130 Ibf (580N) 140 lbf (620N) 40h pass iKf scow's 130 lbf (580N)

IIIC RO 70R 32h borderline fail 155 lbf (690N) 120 lbf (530N)

RO 70H 16h fail 85 lbf (380N) 95 lbf (420N) ^RO 70P 16h fail 75 IDT (.oiUNJ 80 lbf (360N)

"RO 76A-1 pass 120 lbf (530N) 130 lbf (580N) HID RO 77B-1 fail 60 lbf (270N) 80 lbf (360N) Re-refined base stock 40 lbf (180N) 45 lbf (200N) Paraffinic mineral oil 30 lbf (130N) 40 lbf (180N)

With one exception, the IIIC and HID reference oils are ranked approximately in the same order as in the sequence tests. The exception, reference oil 70R, gave an exceptionally

high pass load. The results were inconsistent, however, in that the minimum fail load was

lower than the maximum pass load. Additional tests and study are clearly warranted. It should also be noted that the two unformulated base oils were ranked decidedly lower than the formulated oils in table 5. According to the criteria set forth earlier for judging the value of a test method, the Suntech Timken test exhibits a high degree of sensitivity to different oils and shows a high degree of correlation with service performance. The repeatability has not yet been established.

7. Conclusions

7.1. Pin and V-block test methods

1) The Falex #0 machine is compact and easy to operate. These features, however, belie complexities that are connected with load calibration and effects associated with the multiple contact specimen configuration. 2) ASTM D2670 is, in general, too severe for application to unformulated and formulated engine oils. 3) Applicable wear rate tests may

be developed using lower loads. A procedure designed to measure wear at a series of increasing load steps which gives a wear rate vs load characteristic curve for the lubricant

may be more useful than measurement of wear at a single load. 4) ASTM D3233 can be applied

to measure the load carrying capacity of some formulated engine oils. A procedure utilizing

a run-in load of 50 lbf can be applied to base oils and formulated engine oils. 5) Specimens which met specifications described in ASTM D2670 and D3233 were found to yield different

results because of differences in microstructure. 6) The extent to which pin and V-block

test procedures can be used to demonstrate consistency and evaluate service performance has

not yet been fully evaluated, however, the existing ASTM test methods do not appear to offer

much promise in this regard.

7.2. Ring and block methods

1) ASTM D2714 can be applied to base oils and formulated SE engine oils. Repeat- abilities ranged from 6 percent to 20 percent (standard deviation as percent of average). There was little discrimination among the base oils and formulated oils to which the test

was applied. 2) A modification of ASTM D2782, the Suntech Timken test, appears to offer

some interesting promise in discriminating among and ranking IIIC and HID reference oils.

The authors wish to express their thanks to Dr. A. W. Ruff and Dr. S. M. Hsu for helpful discussion and valuable advice.

257
Friction Force

Bloc* T«W—

'

R. 0. 76A-I at I30lbf (578N) L

A condit . curred dur
[1] Gates, R. and Hsu, S. , The four-ball wear test for engine oil evaluation (these pro- ceedings).

[2] 1979 Annual Book of ASTM Standards , Part 24, Petroleum Products and Lubricants (II), American Society for Testing and Materials, Philadelphia, PA (1979).

[3] Crowley, C. A. and Faville, F. A., Evaluation of extreme pressure lubricants, SAE Regional Transportation Meeting, Chicago, IL (October 1937).

[4] Faville, F. A. and Faville, W. A., Falex procedures for evaluation lubricants, 23rd ASLE

Annual Meeting, Cleveland, OH (May 1968).

[5] Pin and V-block Machine Instruction Manual, Favil le-LeVally Corp., Downers Grove, IL. [6] Tabor, D. , The Hardness of Metals , Clarendon Press, Oxford (1951).

[7] Mecklenburg, K. R. , The Effect of Wear on Compressive Stress in the Sphere-on-Plane and Multiple-Flat-on-Curve Configurations, Technical Report AFML-TR-73-39 (February 1973).

[8] Ryan, V. A., Measurement of lubricant film strength in the region of boundary friction, Lubrication Engineering, p. 101 (1946).

[9] Friction and Wear Devices , 2nd edition, American Society of Lubrication Engineers, Park

Ridge, IL (1976). [10] F. E. Didot, Suntech Corp. , private communication.

259

National Bureau of Standards Special Publication 584. Proceedings of Joint Conference

on Measurements and Standards for Recycled Oil /Systems Performance and Durability held at

NBS, Gaithersburg, MD, October 23-26, 1979. (Issued Nov. 1980) THE FOUR-BALL WEAR TEST FOR ENGINE OIL EVALUATION

Richard S. Gates and Stephen M. Hsu Tribochemistry Group

Chemical Stability and Corrosion Division

National Bureau of Standards Washington, DC 20234

1. Introduction

Bench tests are an attractive approach to wear testing. Their low cost, short duration, and ease of operation make them a desirable research tool. The commonly used engine

sequence tests have been established based on actual field performance [l] 1

, but they are complicated and depend on so many parameters that chemical effects are often masked. Laboratory bench tests can be tightly controlled to show differences existing in base stocks or additives. A simple bench test that correlates with performance and has the sensitivity to measure chemical effects would be invaluable in determining the effects of possible contaminants on engine oil performance, and also effects on additive response. The object of this study is to evaluate various test procedures for evaluating the wear characteristics of engine oils. The test procedures are being evaluated on the basis of sensitivity, repeatability and correlation with engine wear data. The four-ball wear tester was chosen for this study for several reasons. The test apparatus is available commercially and used extensively in industry for wear testing. The test is easy to conduct, well controlled, and uniform test specimens are available at low cost. In any wear testing, the specimens basically undergo a destructive evaluation

process. Test repeatibi 1 ity , therefore, depends heavily on the uniformity of the test

specimen. In the four-ball test, extra polish ball bearings with roundness specification

of 0.00001 in are readily available at low cost. Several workers have examined various procedures associated with four-ball test

[2-8]. Generally these are: 1) slow speed sliding vs load, 2) fast speed sliding vs load, 3) step loading seizure test, 4) sequential testing. These procedures, except for the sequential testing, will be examined in this study. The sequential testing is not possible on our 4-Ball machine due to equipment design.

2. Experimental Apparatus and Procedures

The apparatus used in this study is a Falex #6 machine manufactured by Faville LeVally

Corp. It consists of three balls clamped in a planar configuration in an oil cup, with

the fourth ball rotating on top of the other three. The load on the contact points was controlled by weights on a lever arm arrangement capable of giving vertical loads of over

500 lbs. The temperature of the bulk oil was controlled by a heater located in the wall

of the test cup. The torque produced by the contact was measured by a force transducer

which gave a continuous readout to a strip chart recorder. The original design had a test

cup that called for 85 ml of lubricant for each test. A modified test cup was constructed

that required only 10 ml of lubricant for each test. This gave more tests for a limited

amount of sample and also allowed for easy sample retrieval for wear debris analysis. Wear was evaluated by measuring the diameter of the wear scars on each of the three stationary balls. The average of the three wear scar diameters was then used to calculate

the wear scar volumes according to the work by Feng [9]. Figures in brackets indicate the literature references at the end of this paper.

261
3. Test Specimen Preparation

Since thorough cleaning is important in ensuring test precision, the following pro- cedures were used.

3.1. Initial batch cleaning of ball bearings

The balls were agitated ultrasonical ly for 2 minutes in successive baths of hexane, Stoddard solvent, and acetone. The acetone was drained off completely and the balls were

kept under hexane until ready for testing.

3.2. Test cup and top ball holder cleaning After removing all excess oil with a tissue, the parts were rinsed in successive

solutions of hexane, Stoddard solvent, and acetone. After cleaning with a clean dry lintless tissue, the parts were dried with nitrogen gas.

3.3. Final cleaning of ball bearings Just prior to testing, 4 balls were selected from the initially cleaned batch and agitated ultrasonical ly for 1 minute in successive baths of hexane with 10 percent Stod- dard solvent, and acetone. The balls were wiped with a clean dry lintless tissue and dried with nitrogen gas. Three of the clean balls were placed in the text cup and clamped in place. The 4th

ball was placed on top of the other three and 10 ml of lubricant were added to the cup. The ball holder assembly was then ready to be placed onto the loading assembly for

testing. Upon completion of a test, wear scar measurements were made using a 100 x microscope with a calibrated graduated reticle reading to the nearest 0.01 mm.

4. Criterion for Correlation

The comparison between bench test performance and actual engine performance was made using ASTM engine test standard reference oils. The current reference oils on M.S. sequence HID engine test were used. Data from HID Engine Sequence Tests taken from ASTM Sequence HID Surveillance Panel Reports, showed that it was possible to group the oils into two categories with respect to wear as shown in table 1 and figure 1. Reference Oils 76A, 75B, and 79A were classified as low wear oils while 77B and 77C could be classified as relatively

high wear oils. The performance of the reference oils in the bench tests as compared to the wear classifications to determine if there was a correlation. Table 1. HID engine sequence data-reference oils. Reference Average Cam Standard Engine

Oil SAE Viscosity and Lifter Wear Deviation Test # of RE0 Grade cm x 10 4 cm x 10 4 Ranking Tests

76A 10w-40 48 23 Low 17 75B 10w-30 46 25 Low 10 79A 10w-30 48 15 Low 7 77B 10w-40 287 188 High 22 77C 10w-30 277 130 High 22

5. Results and Discussions

5.1. Procedure evaluation

Two reference oils RE0 76A and RE0 77B were selected for initial screening of the speed

setting. Since reference [10] showed ZDDP is an effective anti-wear agent in this load range,

all of the reference oils contain zinc dithiophosphate (ZDDP) as the antiwear agent, the load

is set at 23 kg machine loading (50 lbs). 262
400

I ± 1 St. Deviation

100 -

75B 79A 77B

Reference Oils Figure 1. Engine sequence test wear ranking of reference oils. Figure 2 shows the relationship between wear volume and speed on a log-log plot. At about 800-850 rpm, the data suggest a transition point. To examine this more closely, the data

are replotted in figure 3 as wear rate (wear volume/unit linear distance traveled) versus

speed. This shows that the rate of wear is actually higher at slow speed (100 to 800 rpm) and levels off from 800 to 2000 rpm. This may be explained as follows. As speed increases,

the viscosity effect or hydrodynamic component increases as the wear process proceeds

during each run. In other words, this also represents the transition of boundary lubrication

into the elastohydrodynamic lubrication regime. Using this information, two speeds were

selected to represent the predominant boundary lubrication (200 rpm) and elastohydrodynamic

(EHD) lubrication (1500 rpm) modes. It should be recognized that each mode contains a component of the other in it. 263
3 4 5 10 Speed, rpm x 102 20

Figure 2. Wear volume as a function of speed. Using these sets of conditions, tests were run using the entire set of Sequence HID

engine test reference oils. Table 2 shows that there was no correlation with engine sequence wear data for either mode.

5.2. Oxidation-wear coupled test procedure

The effectiveness of a boundary lubrication film is primarily a function of the chemical composition of the lubricant. Zinc dialkyl dithiophosphate (ZDDP) is the antiwear

additive of most crankcase lubricants. ZDDP functions not only as an antiwear agent, but also as an anti-oxidant. Table 2. Basic 4-Ball wear test data - reference oils. Common Conditions: Load: 23kg Temperature: 75 °C Duration: 60 min

Fluid: 10 ml REO 200 RPM

79A

75B

76A 77B

77C

Engine Test Wear Ranking

Low

Low Low High High

Wear Volume

cc x 10

7 2.6

2.5

2.2 2.1

1.6

Ranki ng

54

32

1

Wear Volume

cc x 10-7 6.1

5.8

6.6

3.8

2.4

Ranking

4

35

21 264
I I I i

I I I I I I I I 1 2 3 4 5 10 20 30 Speed, rpm x 102

Figure 3. Wear rate as a function of speed.

In the engine test, the oil undergoes oxidation/thermal degradation and metal catalysis. ZDDP functions as an anti-oxidant by forming coordination complexes with the peroxide radical which initiates the oxidation process [11]. As oxidation progresses,

ZDDP is used up as anti-oxidant leaving little or no ZDDP to function as the anti-wear

agent. A point will be reached at which both oxidation and wear would proceed at an accelerated rate due to loss of protection because of additive depletion. If this hypothesis is true, then a wear test coupled with an oxidation procedure could reverse the ranking observed in the slow sliding experiments. The oxidation was introduced by way of

an open tube oil thickening test prior to the wear test. The oil thickening test con- sisted of bubbling air through a 100 ml sample of oil 10 ml used oil from a batch of automotive crankcase used oil was added as catalyst. The tube was kept at 177 °C (350 °F) and the thickening of the oil was monitored with a capillary micro viscometer. The capillary micro viscometer constructed for these measurements required only 2 ml of sample.

The data are calibrated with reference oils of known viscosity at 40 °C. The set of 5

- HID reference oils were oxidized under identical conditions using the open tube apparatus. The oil thickening rates did not correlate with the results of the HID Engine Sequence

Tests as shown in figure 4 and table 3. This may be due to the absence of several conditions

that were present during the engine sequence test - fuel dilution, constant addition of wear particles and fresh metal surfaces, water, and N0

x and other blow-by gasses. Wear

tests were run to observe the effects of oxidation on the antiwear characteristics of the reference oils. Again 200 rpm and 1500 rpm were chosen. The 200 rpm runs showed the greatest change in ranking, as shown in table 4. The 77B oil has the highest wear just as

in the engine sequence tests. The other high wear oil 77C, also moved up in the ranking

so that it was no longer the lowest wearing oil as shown in table 5. The results are encouraging and show that the oxidation is affecting the antiwear properties of the oils,

and that it affects the antiwear properties of the high wear reference oils more than the

low wear reference oils. 265
Oxidation Time, hrs.

Figure 4. Viscosity increase in oil thickening test. Table 3. Oxidation break point of reference oils. Engine Sequence Test Oil Thickening Test Oxidation Break Point3

, Oxidation Break Point , REO Hours Hours 76A 64 48

75B 56 48

79A 40 64

77B 24 64

77C 16 64 Oxidative break point was determined according to ASTM HID Engine Sequence Test Method (375% viscosity increase).

266
Table 4. 4-Ball wear test data - oxidized reference oils Common Conditions: Load: 23 kg Temperature: 75 °C Deviation: 60 min

Fluid: 10 ml REO Oxidized 48 h 200 RPM 1500 RPM Engine Test Wear Volume Wear Volume

REO Ranking cm3 x 10~7 Ranking cm3 x 10"7 Ranking

79A Low 3.8 4 5.4 3 75B Low 3.2 1 5.8 4 76A Low 3.5 2 5.4 2 77B High 4.9 5 7.4 5 77C High 3.6 3 4.5 1 Table 5. Comparison of 200 RPM basic wear test data reference oil vs oxidized reference oil. Common Conditions: Load: 23 kg Temperature: 75 °C Duration: 60 min

Speed: 200 RPM Unoxidized Reference Oil Oxidized Referemce Oil Engine Test Wear Volume Wear Volume

REO Ranking cm3 x 10~7 Ranking cm3 x 10"7 Ranking

79A Low 2.6 5 3.8 4 75B Low 2.5 4 3.2 1 76A Low 2.2 3 3.5 2 77B High 2.1 2 4.9 5 77C High 1.6 1 3.6 3 5.3. Step-loading seizure test

There are several variations of seizure tests using a four-ball configuration. One method is to run wear tests at different loads with the results plotted on log-log paper. This is the classical load capacity test. It defines the transition point between the low wear and the high wear region. Oils can be compared either by the transition load or the

final seizure load. This procedure is time consuming. The method examined in this study

is a variation of the above mentioned procedure. It uses the friction characteristic to define seizure point in discrete steps of increasing loads. One typical friction trace is shown in figure 5. At point A, the friction force as represented by the torque increases

dramatically. This load, therefore, is defined as the seizure load. Initial testing was done using a candidate oil from each of the high wear (77B) and

the low wear (76A) groups. A step loading increment of 20 lbs was selected because incre- ments of 100, and 50 lbs lacked sensitivity, and increments of 5 or 10 lbs were impractical

due to time and equipment limitations. A speed of 200 rpm was selected for the tests based

on the results of preliminary testing shown in figures 6 and 7. The seizure point, depicted here as a rapid increase in the coefficient of friction,

shows that at 600 rpm, the difference in the seizure loads of the two oils was only 9 kg. At 200 rpm the difference was enhanced to 54 kg. Slower speeds were not selected because

the seizure load would have been too close to the 227 kg load limit of the equipment. The seizure tests were run therefore at room temperature, 200 rpm, and with 9 kg increments

until seizure occurred. The load at which seizure occurred was used to rank the oils. 267
Figure 5. Typical friction trace for step-loading four-Ball seizure test.

Torque-

— REO 77B REO 76A "^TA A-T, A A -O1 _

! 1 1 1 3 45 91 136 181 Load, kg

Figure 6. Step-loading seizure test at 600 RPM. Table 6. 4-Bal

1

step loading seizure test data - reference oils. Common Conditions: Speed: 200 RPM Temperature: Ambient

Duration: 5 minutes/load

Loading Increment: 9 kg/level Seizure Load Engine Sequence

REO # of Tests isa Seizure Test Wear Ranking

77C 1 127 5 High

77B 2 145, 163 4 High

76A 2 200, 200 3 Low 79A 1 218 2 Low 75B 1 227 1 Low

15

10

268
* 15 £ 10

oo

REO 77B REO 76

A

45 91 136 181 Load, kg

Figure 7. Step-loading seizure at 200 RPM. The results obtained from the entire set of five reference oils shown in table 6, had

a good correlation with the Engine Sequence Ranking and shows that the step loading seizure

test appears to have the capability and sensitivity to distinguish between the two groups

of oils.

6. Conclusions

In this study, several procedures using the four-ball wear tester have been evaluated

using the ASTM engine reference oils. Based on the experimental results the following conclusions can be reached:

1) The normally used slow-sliding and fast-sliding 4-Ball wear procedures did not rank the reference oils correctly.

2) The oxidation coupled slow-sliding wear test procedure gave encouraging results

to correlate with engine tests.

3) The step-loading seizure procedure correlated the five reference oils correctly.

Both the oxidation-wear coupled and seizure test procedures will be examined further. Wear

debris analysis and differential infrared spectroscopy will be used to investigate the mechanism in these procedures. References

[1] Groff, W. P. Jr., Roberts, C. E. , and Lepisto, P. R. , New lubricant test procedures

for gasoline engines from the viewpoint of an independent research lab, ASLE Preprint

No. 79AM- lc-1, pp. 1-13 (1979).

[2] Brown, E. D. , Friction and wear testing with the modern four-ball apparatus, Wear,

17, 381 (1971).

[3] Miller, A. H. , Considerations in interpreting four-ball data, Wear, 23, 121 (1973).

[4] Feng, I. M. , A new approach in interpreting the four-ball wear results, Wear, 5, 275 (1962).

269
[5] Fein, R. S. , Measurement of wear volume and interpretation of results with four-ball machines, Proc . 2nd Annual Conference of ASME Lubrication Division , Philadelphia,

PA (1959).

[6] Clinton, W. C. , A Study of the Four-Ball Machine, NRL Report 3709 (Sept. 1950).

[7] Klauss, E. E. and Bieber, H. E. , Effects of some physical & chemical properties of lubricants on boundary lubrication," ASLE Trans., 7, 1, 1964.

[8] Fein, R. S. , Transition temperatures with four-ball machine," ASLE Trans., 3, 34 (1960).

[9] Feng, I. M. , A new approach in interpreting the four-ball wear results, Wear, 5, 295-288 (1962).

[10] Hsu, S. M. , Anti-wear & lubricity additives for lubricants, Proc . of the MFPG Symposium on Engineering Design , NBS SP 487, pp. 172-180 (1977). [11] Willermet, P. A., Mahoney, L. R. , and Bishop, C. M. , Lubricant degradation and wear

II. Antioxidant capacity and ir - spectra in systems containing zinc dial kyldithio- phosphates, ASLE Reprint No. 79-AM-1B-3, pp. 1-6 (1979).

270
National Bureau of Standards Special Publication 584. Proceedings of Joint Conference

on Measurements and Standards for Recycled Oil /Systems Performance and Durability held at

NBS, Gaithersburg, MD , October 23-26, 1979. (Issued Nov. 1980)

APPLICATON OF DIFFERENTIAL SCANNING CALORIMETRY

TO THE CHARACTERIZATION OF LUBRICATING OILS

James A. Walker and Wing Tsang

Chemical Kinetics Division

Center for Thermodynamics and Molecular Sciences

National Measurement Laboratory Washington, DC 20234

High pressure differential scanning calorimetry (DSC) has been used

to characterize the oxidative stability of formulated as well as virgin

and recycled lubricating base stocks. At pressures of 0.7-3.4 MPa (100-500 psig) air or 0 2 and temperature near 200 °C, degradation occurs with significant generation of heat. Experiments conducted in the tem- perature programmed mode give recognizably different thermograms as well

as onset temperatures for various lubricating oils. In the isothermal mode induction time measurements were carried out with ASTM Engine Test Standard Reference Oils (R0) which contain antioxidants and appear to correlate with multicycl inder engine sequence test results. Under the same experimental conditions virgin base (VB) and recycled base (RB) stocks degradate too quickly to measure the induction time. The dependence of induction time and peak width on pressure and temperature as well as measurements of heat output are described. The

speed, accuracy and experimental configuration of DSC measurements suggest

its use not only for elucidating fundamentals on the mechanism of hydro- carbon oxidation but also as a standard test method.

1. Introduction

Thermal analysis [l] 1 is today increasingly used as an important method for the characterization of complex organic systems. The technique involves monitoring a particular

property of the system with the change of temperature or, in the isothermal mode, with time. The thermograms provide a "fingerprint" of the material similar to and as unique as an infrared spectra or a boiling point range. Proper interpretation of this characteristic can yield

important information on the physicochemical processes that are actually occurring in the

sample. Thermal analysis requires only a small volume of sample and this has made heats of reaction an increasingly attractive parameter for measurement. Thus differential scanning

calorimetry (DSC) has become one of the most popular methods for carrying out thermal analysi

Noel and co-workers [2,3,4] were among the first to realize the potentialities of DSC

for characterizing complex lubricating oils. The highly specific techniques such as mass spectroscopy or infra-red spectroscopy sometime yield too much information, with the result

that interpretation becomes difficult. On the other hand, some of the ASTM tests measure

gross properties or are carried out under conditions vastly different from actual in-service

environment. In DSC, the use of small samples (< 2 mg) suggests that experiments are carried

out under thin film conditions, thus simulating in this respect actual engine conditions.

Furthermore, the test temperatures are quite high and thus again approach use conditions.

The salient result of Noel [2,3] was the demonstration of the capability of carrying out such

studies above ambient pressures. This is manifested by an exothermic reaction at about

200 °C. More specifically, he demonstrated (a) increased induction time with increasing in- hibitor concentration up to a maximum value; (b) the effect of metal additives in lowering

threshold temperatures; and (c) different threshold temperature and induction times for various types of additives.

1 Figures in brackets indicate the literature references at the end of this paper.

271
The present studies are aimed at exploring the possibility of using DSC as a standard

test method for evaluating the oxidative stability of lubricating oil, and further to use the technique to study the basic mechanisms involved in hydrocarbon oxidation processes.

2. Experimental

All experiments were made using a DuPont Model 990 Thermal Analyzer with a model 910 high pressure differential scanning calorimeter module. A schematic of the reaction cell can be seen in figure 1. The experimental procedure involves placing a 1 to 2 mg sample in an open aluminum pan, setting the pressure and flow rate of the purge gas - air, oxygen, or nitrogen - and then commencing the experiment either by running the temperature up to a preselected value, holding it at this point and observing the reaction heat as a function of time (isothermal ex- periment), or by scanning at a programmed temperature rate and measuring the incremental heat change as a function of temperature (oxidation onset experiment). For some of the isothermal experiments where induction times are very short the cell was charged to the operating pres- sure with N 2 at the desired flow rate, and the temperature rapidly raised to the isothermal temperature. At that time 0 2 was introduced and the time scan started simultaneously. PRESSURE DSC CELL

Top "O" Ring

Figure 1. Schematic of DSC cell. 272
A great deal of attention was given to finding the conditions that yielded an optimum

amount of reproducible information and indeed it proved to be possible to increase the precision by an order of magnitude in comparison with the earlier work. The conditions that were used for most of these studies were 3.4 MPa (500 psig) oxygen [6] for isothermal experiments and 0.7 MPa (100 psig) air and 20 °C/min heating rate for oxidation onset temperature

studies. All experiments were carried out with flow rates of 50-120 cmVmin (NTP). This was necessary to continually remove reaction products and to assure maximum contact between the sample and the reactive gas. The pressures used in these experiments are a reflection of the need to obtain sharp onsets as well as maintaining details in the thermograms.

3. Results and Discussion

Examination of the samples subsequent to DSC analysis indicates that the process that is observed is mainly one of progressive oxidation. The former undoubtedly involved both degradation as well as polymerization. Evidence of degradation can be seen at the end of the temperature programmed runs at * 360 °C where we obtained a shiny black enamel. From the isothermal experiments with reference oils one obtains somewhat darkened samples of increased viscosity and. a sticky consistency. For the virgin and recycled base oils there were only changes in color. Figures 2 through 4 represent thermograms of experiments carried out in the programmed

temperature mode for the three types of oils under consideration. It is clear that there are definitive and generic differences with regard to the oils. As perhaps could be expected and

in conformity with the observation of Noel and Cranton [4], the reference oils show the sharpest and latest onsets. Note that in some of these figures replicate runs are displayed,

but with varying sample sizes and the results are indicative of the reproducibility of the

data. It demonstrates that for this measurement sample size is not a controlling variable.

The virgin base oils on the other hand display the slowest onset and a corresponding low threshold temperature. Finally, the recycled base oils appear to belong in an intermediate

category. The simplest explanation for these observations is that the basic process is that

of free radical polymerization. In the reference oils this process cannot occur until the inhibitor is destroyed. Since the rate of polymerization has an Arrhenius dependence on temperature, the higher temperatures which bring about the demise of the inhibitor also means that the initially observed rate must be much faster than in the case where additive is not

used. For the virgin base oils there appears to be a reactive component which is apparently

not present in the recycled base oils. One can well visualize that through use this reactive

portion of the substrate will be destroyed. Alternatively, it is possible that the recycled

base may still contain some of the additive and thus the higher onset temperatures. Quantitative results on the onset temperatures are summarized in table 1. The uncertainties (± 1.7 °C) listed in the table give a good indication of the precision of these

tests. In the case of the reference oils it should be noted that while the onset temperatures are in agreement with respect to the best and worst of the lot (compared to ASTM

III-C engine sequence tests) [5] there is confusion at the intermediate levels.

In particular one notes the inversion of the order between the fail and borderline classification from the engine tests and the DSC measurements. Note that these results are confirmed by induction time measurements to be described subsequently. Of course, an engine

test represents an integration of all factors and there is no reason why a test for oxidative

stability should display an exact correlation.

We now come to induction time measurements. Typical results for ASTM III-C Reference

Oils can be found in figure 5. Under identical experimental conditions for the virgin base

stocks and the recycled base stocks, there is an immeasurable short induction period. Unless

conditions are very carefully set, oxidation occurs during the run-up to the desired

isothermal temperature. Results of experiments at 0.4 MPa (50 psig) N 2 /0 2 and 185 °C give

curves as seen in figure 6. For comparison we show results for a similar experiment with a reference oil sample in figure 7. Shapes and sizes are completely different. This clearly

indicates that different processes are at work. One suspects that under these conditions the recycled and virgin base oils are in an inherently unstable regime just prior to "explosion".

It should be pointed out that Noel and Cranton [4] were apparently able to obtain an isothermal curve for a virgin base oil that was very similar to what they obtained for the case where inhibitors were added.

27 3
VIRGIN BASE STOCKS

ENDO

VB5066

AIR 0.7 MPa (100 psig) f\ 120 cm3/Min (NTP) / 20°C/Min /

100 200 300 VB5067 A

194 /s

i ' / i ~ i 100 200 300 VB5065 C\

185 A

i i i i i i . . i i i 100 200 300

Temperature, °C

Virgin base oil (VB). Oxidation onset temperature vs.

274
RECYCLED BASE STOCKS

EXO

ENDO

RB1388 RB1389

AIR 0.7 MPa (100 psig) . 120 cm3/Min (NTP) /

20°C/Min /

208a/ 207 V

iii i 71 i i i 1 i 1

i 100 200 300 100 200 300

RB1390 RB1391

204 ^ /

' i

i

i ill ii i

207 \J

, . I . , ' iii i 100 200 300 100 200 300

RB1392 RB1393

206 -x / 206^ /

, . I i , , 100 200 300 100 200 300 Temperature, °C

Figure 3. Recycled base oil (RB). Oxidation onset temperature vs. Aq.

27 5
EXO

7

i

ASTM \J 1 1 VI IMC 111 \J REFERENCE 1 8 Ism 1 & 1 1 L» 1 « Eh OIL V/ 9 Lb R05179 TOR 10W-30

Purge Gas Air Pressure 0.7 MPa (100 psig) Flow Rate 120 cm3/Min (NTP) Heat Rate 20°C/Min

j_ 1 meal/sec

229

J I

v 229_^xJ

v --^

V I

I

I I I I -229, i 60 140 220 300 Temperature, °C

Figure 4. Typical ASTM III-C reference oil. Oxidation onset temperature vs. Aq.

276
EXO

ENDO

Purge Gas 02 Pressure 3.4 MPa

Flow Rate 120crr)3/Min Temp. 185°C R05173

/

I (500 psig)

I I (NTP) ASTM IIIC REFERENCE OIL 10W 70P 16 HR ENGINE SEQUENCE TEST }

V

T 1 meal/sec

^22.5 —'

As.22.5 MirO—_________

i

1 I 0 20 40 0 20 40 Time, Min

Figure 5. Induction time vs. Aq for typical ASTM III-C reference oil for three runs with different sample sizes (0.5 mg, 0.75 mg, and 1.5 mg).

277
Time, Min

Figure 6. Induction time vs. Aq for a virgin base and a recycled base oil @

185 °C and 0.4 MPa (50 psig) N2 /02

.

278
ENDO

ASTM IMC REFERENCE OIL

71 B 10W-30

R05177

0 0.3 MPa (50 psig) 70 cm3/Min(NTP) 185°C

^1.0mcal/sec

r

« « i . i i i i . 0 10 20 30 40 Time, Min

Figure 7. Induction time vs. Aq for an ASTM III-C reference oil at 185 °C and

0.3 MPa (50 psig) 0 2

.

1

279
Table 1. Compilation of oxidation onset temperature data for virgin base, recycled base, and ASTM III-C reference oils. ASTM III-C

3 Reference Oil Samples ASTM

Code

°C Std. Dev. ASTM III-C Engine Sequence Tests R05170/5171 71B 260.5 1.4 Pass R05174/5175 76A 254.7 .6 Pass R05173/5176 70P 254.2 .7 Fail R05172/5179 70R 228.9 .2 Borderline R05177/5178 70H 224.4 1.5 Fail Recycled Base Stocks

RB1387 202.6 2.4 RB1388 208.0 1.8 RB1389 206.8 1.3 RB1390 204.0 2.5 RB1391 206.7 2.1 RB1392 206.2 1.6 RB1393 206.3 2.5 Virgin Base Stocks VB5065 184.6 2.7 VB5066 183.5 1.5 VB5067

Purge Gas

193.

8

Air

2. 2

Heating Rate 20 °C/min Pressure 0.7 MPa (100 psig) Flow Rate 120 cm

3 /min (NTP) Blind duplicate samples. Table 2 summarizes the results of induction time measurements on the reference oils. The uncertainties are of the order of 4.5 percent and permits a clearer discrimination

between the reference oils than onset temperature measurements. It should be noted that induction time data in table 2 track the onset temperature data in table 1 exactly and thus also show the discordance in the middle range between the ASTM III-C engine and DSC tests.

280
Table 2. Compilation of induction time data for ASTM III-C reference oils. 5TM III-C eference Oil amples 35170/5171

35174/5175

35173/5176

35172/5179 35177/5178

ASTM

Code

71B 76A

70P 70R

70H

Time, Min.

43.2

31.0 23.0

13.9

8.7

1.85 2.58

.82

. 56 .22

ASTM III-C Engine Sequence Tests

Pass Pass

Fail Borderl ine

Fail

Purge Gas Pressure

Isothermal Temp.

Oxygen

3.4 MPa (500 psig) 50-120 cc/min (NTP) 185 °C Figure 8 indicates the effect of oxygen pressure on induction time as well as the shape

f the exothermic polymerization process. The induction time is roughly linearly dependent

n 0 2 and is indicative of the fact that the inhibitor is being destroyed by a reaction

raceable to the presence of oxygen. This is opposed to the claim of Noel and Cranton [4] nat it is the thermal stability of the inhibitor that controls anti-oxidant behavior. We

onclude that it is the resistance of the inhibitor to oxidation that is the controlling

actor. This in turn raises an interesting point. The actual gas encountered by the jbricating oil in an engine is more like a NO mixture, and thus may well have different

ehavior patterns, especially since nitration &ust also be important. Clearly experiments

ith more realistic gas mixtures are called for. It is possible that the disagreement

etween engine test results and the present DSC tests may be due to this artifact. The shape

f the reaction exotherm is a reflection of the complex chemical kinetic processes that are

ccurring during the oxidation process. One notes the expected dependence as manifested by ncreasing peak width with decreasing oxygen concentration.

Figure 9 represents the effect of temperature on induction time and peak shape (half

idth). These results are in accord with activation energies of about 84 kJ, in accord with

hat one expects of auto-oxidation reactions. Finally, table 3 summarizes the data on the

sat released during the exothermic reaction from the present study on the reference oils,

lese numbers are in the expected range for polymerization processes. They do not correlate

ith oxidative stability data. Similar results have been observed by Noel and Cranton [4],

ho have in fact separated different fractions of lubricating oil and have shown that they

re characterized by differing heats of reaction. The variation in the heats of reaction are

trongly indicative of the differences in the polymerization process as it occurred in each

Hi! Overall, we believe that DSC has interesting potential as a test method for total xidation resistance. This is of course dependent on the quantity of inhibitor present, but

s also sensitive to different types of inhibitors. It should also be dependent on other

roperties related to rates of oxidation, such as dispersant concentration and viscosity,

he precision and accuracy of our experimental results suggest the possibility of an xtremely fine scale. We note that the differential nature of these measurements make it articularly suitable for tests with an internal standard. Thus, if we use a designated

ompound as a borderline reference we can simultaneously measure the exothermicity of eference and unknown in the same experiment with results that should be quite free from

ossible operator errors. With regard to properties as such, it is quite clear that recycled

281
base oils and virgin base oils differ in the amount and nature of some of the constituents.

However, it is unclear at present what effect, if any, this may have on performance since the additives have such great effects.

Figure 8. The effect of 0 2 pressure at 185 °C on the induction time of an ASTM

III-C reference oi 1

.

282
TEMPERATURE DEPENDENCE

Figure 9. The effect of temperature at 3.4 MPa (500 psig) 0 2 on the induction

time of an ASTM III-C reference oil.

283
Table 3. Compilation of heat output data for ASTM III-C reference oils. ASTM III-C Reference Oil ASTM kJ/Gram Std. Dev. Samples Code R05170/5171 71B 7.1 0.11 R05172/5179 76A 7.4 0.23 R05173/5176 70P 6.9 0.11 R05174/5175 70R 4.7 0.19 R05177/5178 70H 5.3 0.22

Purge Gas Oxygen

Pressure 3.4 MPa (500 psig) Flow Rate 50-120 cm

3 /min (NTP) Isothermal Temp. 185 °C References

[1] Porter, R. S. and Johnson, J. F. , Analytical Calorimetry, 3 (Plenum Publishing Company, New York, 1974).

[2] Noel, F., J. Inst. Petroleum, 57, 354 (1971). [3] Noel, F., Thermochemica Acta, 4, 377 (1972).

[4] Noel, F. and Cranton, G. E. , Analytical Calorimetry, 3, 305, R. S. Porter and J. F. Johnson, eds. (Plenum Publishing Company, New York, 1974).

[5] Private communication from Dr. S. Hsu, Tribochemistry Group, NBS. [6] R. 0. Blaine, DuPont Instruments Applications Brief Number TA 41.

234
National Bureau of Standards Special Publication 584. Proceedings of Joint Conference

on Measurements and Standards for Recycled Oil /Systems Performance and Durability held at NBS, Gaithersburg, MD, October 23-26, 1979. (Issued Nov. 1980)

EVALUATION OF BASESTOCK AND FORMULATED LUBES USING THE PENN STATE MICROOXIDATION TEST

E. Klaus, V. Krishnamachar, and H. Dang Pennsylvania State University

133 Chemical Engineering Building University Park, PA 16802

The microoxidation test has been developed at Penn State and used successfully for the evaluation of new and used ester based aircraft gas turbine lubricants. This system combines a simple thin film oxidation

test with two analytical systems for primary analysis. First, the oxidized fluid is evaluated in a Gel Permeation Chromatograph with both refractive index and U-V detectors. The second analysis utilizes an atomic absorption spectrometer. In addition, samples prepared from GPC analysis can be used for infrared, ultraviolet, and NMR analyses.

This presentation will discuss current efforts to adapt this micro- oxidation test for use with petroleum lubricating oils, and to evaluate

both base stocks and formulated lubricating oils.

1. Introduction

A new thin-film oxidation test has been developed for the quantitative evaluation of aircraft gas turbine (ester) lubricants [l] 1

. Problems associated with diffusion limitation

are minimized by the use of a small sample (20-200 u£) with a relatively large fixed area of fluid-gas contact. Analysis with gel permeation chromatography (GPC) gives a semi-quantitative measurement

of additive depletion, and measures the quantity of original fluid reacted and the quantities

of oxidized products formed. By a careful calibration under a nitrogen atmosphere, the volatility loss is measured and calculated independently of the oxidation reaction. Test repeatability is excellent. The system is adaptable for a wide range of time-temperature

studies and allows the duplication of system conditions in equipment, such as in the aircraft

gas turbine lubrication system. A wide variety of catalytic surfaces typical of those found

in structural and bearing portions of the lubrication system can be duplicated. The overall test system is simple to construct and easy to control. In many cases, significant data profiles on a single lubricant can be determined in oxidation tests of 2 to 60 minutes

duration. The additional time for fluid analysis adds only 40 minutes to the oxidation test

time. The GPC analysis is preparative in nature, thereby providing samples of various fractions for further spectrographs analysis [2]. The effectiveness of the test system has been illustrated with dibasic acid ester and polyol ester fluids oxidized on a steel catalyst, with and without oxidation inhibitors. This basic test technique and analytical procedure has been modified and extended for

use with mineral oils and automotive lubricant formulations. The principal modification for

mineral formulations is necessary to identify the oxidation products that are formed in the same molecular weight range as the virgin lubricant.

2. Test Procedure

The oxidation test equipment is shown in figure 1. This unit has been described in detail by Cvitkovic et al . [1] for use with ester lubricants. The basic microoxidation test procedure for esters and mineral oils is the same. The analysis from this test procedure is

1 Figures in brackets indicate the literature references at the end of this paper.

285
designed to show: (a) evaporation of the fluid as a function of molecular weight; (b) the oxidation product as a function of molecular weight; and (c) the remaining virgin mineral oil as a function of molecular weight.

Test Tube

Cover

Gas Supply Hose

Inlet Tube

Outlet Tube < Transite Holder

I Metal Catalyst (Detail)

Figure 1. The microtest oxidation apparatus.

The value of evaporation is determined by the difference in the GPC chromatographs for the original formulation and an evaporation test under nitrogen flow in the same time- temperature conditions used in the microoxidation. The products of the microoxidation test

are separated into two equal aliquots. One fraction is percolated through a clay column [3] to remove all the oxidation products leaving only the virgin hydrocarbon molecules from the

initial formulation. The difference between the evaporation chromatograph and the clay percolation chromatograph shows the amount of the original fluid that is oxidized. The area between the chromatograph for the overall oxidized product and the clay percolated chromato- graph represents the oxidized material as a function of molecular weight. As tests become more severe, some of the high molecular weight product becomes insoluble in the tetra- hydrofuran solvent and can be measured as a deposit weight gain of the test cup. 286
3. Results and Discussion Microoxidation tests for a super refined virgin mineral oil MLO 7828 have been conducted

to illustrate quantitative analysis by spectrum difference. The effect of additive response

in this MLO 7828 base oil is shown by similar differential chromatographic analysis for three additive concentrations and/or combinations. The additives used are zinc dial kyldithio- phosphate at 0.05 percent and 0.15 percent phosphorous and 0.5 percent phenylalphanaphthylamine. This sequence of tests are shown in figures 2, 3, 4, and 5. The evaporation

data are essentially the same for all four fluids. In all cases evaporation appears to resemble equilibrium flash vaporization as opposed to an efficient distillation separation. The amount of oxidized product shows a dramatic decrease as a function of ZDP additive

concentration. The ZDP-PAN combination tends to show the synergistic effect of additives

that control metal coating and oxidation inhibition. In the case of more effective

additive response the amount of oxidized product is reduced substantially. The amount of

high molecular weight oxidation product is reduced by a larger percentage than the overall oxidation product as the inhibitor package becomes more effective.

Figure 2. Analysis by GPC for oxidation and evaporation of a super refined virgin base stock.

287
Molecular Weight

Figure 3. Additive response of 0.05 weight percent phosphorous as zinc

dial kyldithio phosphate.

To establish creditabi 1 ity for the microoxidation test conditions, correlation with lubricant behavior in a 3C engine test is another goal of this program. The time-temperature

relationship for the microoxidation test has been established for aircraft gas turbine

lubricants. Tests of about equal severity are achieved at 200 °C for two hours or 30 minutes

at 225 °C. These two temperatures are in the range of temperatures that appear to exist in the piston ring belt zone of an automotive engine. Some data suggest that temperatures as high as 250 °C exists in the ring belt zone. A series of five 3C reference oils have been used for this test evaluation. The microoxidation test data for these fluids at 200 °C and two hours test time are tabulated on table 1. The five fluids include two that fail, one borderline case, and two fluids that

pass the test. The best columns for correlation are the high molecular weight (1000-10 000

mol. wt. ) and total oxidized product. The problem with the >10 000 mol. wt. product is the apparent loss from this fraction to sludge and varnish. The correlation at 200 °C and two hours is relatively poor.

288
105 104 103 400 200

Molecular Weight

Figure 4. Additive response of 0.15 weight percent phosphorous as zinc

dial kyldithio phosphate. Table 1. Oxidized products in microoxidation tests at 200 °C and 120 min. 3C Test Ox. Prod. % of Orig. (mol. wt.

)

Hours 200-1000 1000-10 000 >10 000 Total 16-1 18.5 13.7 4.9 37.1

16-2 14.5 10.3 1.8 26.6

32 18.0 10.8 5.0 33.7

40 0.4 2.3 1.2 3.9

64 12.9 9.7 5.5 28.7

At 225 °C and 30 minutes the data are presented on table 2. The correlation data look promising based on total oxidized product or oxidized product in the 1000 to 10 000 molecular weight range. The principal problem fluid is the 64 h 3C oil. This fluid has a relatively large amount of polymeric additive which on oxidation appears to show reduced molecular weight rather than increased molecular weight. This fluid is also the most

volatile of the five reference fluids. The increase in temperature from 200 to 225 °C appears to improve correlation with the engine as shown on table 3. 239
Molecular Weight

Figure 5. Synergistic response to pan - zinc dial kyldithio phosphate

additive combinations.

A preliminary test procedure has been conducted at 245 °C to determine the general

trend. This preliminary test is a 30 min test at 245 °C with only 20 u£ of fluid. The tetrahydrofuran insoluble sludge and varnish is the only property measured as shown on table

4. Additional test times of 40 and 60 min were also conducted. The 30 minute tests show

an excellent correlation between sludge and varnish forming tendencies and the 3C engine

ratings. The trend with increasing test time is to approach the same level of varnish asymptotically. From these data it appears that perhaps a larger difference (better correlation) would be achieved in a 20 minute test. Eleven samples of re-refined base stock have been evaluated at 225 °C for 30 min. Total oxidation products as shown in table 5 range from 35.7 percent to 61.6 percent. The amount

of oxidation product in the 1000 to 10 000 molecular weight range differs by more than a fac- tor of two from the best to the worst case. Additive response in the two re-refined base stocks 5100 and 5101 are shown on figures 7 and 8 respectively. In general, the two re-refined

base stocks show additive response that is similar trendwise with the additive response in a super refined virgin base stock (ML07828). The two re-refined base stocks, however, show less oxidation in comparable tests than the super refined virgin base oil and the additive response

of the re-refined oils also appears to be less than for the virgin base stock. It appears

that any inhibitors surviving the re-refining process or "natural inhibitors" may reduce re- sponse to synthetic inhibitors.

290
Table 2. Oxidized products in microoxidation tests at

225 °C and 30 min.

3C Test Ox. Prod. % of Orig. (mol. wt.

)

Hours 200-1000 1000-10 000 >10 000 Total 16-1 25.6 14.7 2.5 42.9

16-2 27.2 9.0 1.9 38.1

32 9.3 8.8 4.6 22.6

40 6.1 2.7 2.0 10.7

64 14.3 9.6 5.3 29.2

Table 3. Evaporation and oxidation in microoxidation test. 200 °C - 120 min. 225 °C - 30 min.

3C Test Evap. Ox. Evap. Ox. Hours 16-1 25.3 37.1 22.2 42.9

16-2 29.8 26.6 23.4 38.1

32 29.3 33.7 31.5 22.6

40 28.7 3.9 26.9 10.7

64 38.5 28.7 32.1 29.2

Table 4. The use of the microoxidation test as a deposition tester. 245 °C, 20 u£

,

Steel Cat.

,

20 ml /min Air

3C Test Microoxidation Time, Min. Hours 30 40 60 16-1 18.5 21.4 22.8

16-2 16.5 23.6 23.9

32 15.8 21.0 21.3

40 9.5 17.4 21.6

64 3.8 15.2 18.8

sludge and varnish on catalyst.

291
Table 5. Oxidized products in microoxidation tests at 225 °C and 30 min.

Ox. Prod. % of Orig . (mol. Wt.)

Base stock

3 Sample No. 200-1000 1000-10 000 >10 00d Total Ox, 5094 32.5 24.3 3. 2 60.0

5095 21.5 21.6 3. 7 46.8

5096 25.7 20.5 3. 4 49.6

5097 24.4 20.6 2. 8 47.8

5098 29.0 19.9 2. 5 51.4

5099 22.3 23.1 2, 7 48.1

5100 28.2 27.8 5. 6 61.6 5101 21.9 12.4 1. 4 35.7

5102 24.2 16.0 1. 3 41.5

5103 25,6 25.0 4. 5 55.1

5104 26.0 24.6 4, 9 55.5

aSeries of re-refined stocks provided by the National Bureau of Standards.

Molecular Weight

Figure 6. A comparison of additive effects on ML0 7828 super refined mineral

oil

292
Oxidized at 225°C, 30 Min.

- 5100 Original

Molecular Weight

Figure 7. Microoxidation characteristics of formulated 5100 re-refined base

oil.

293
Figure 8. Microoxidation characteristics of formulated 5101 re-refined base

oil.

4. Conclusions

A microoxidation test procedure has been adapted for use with mineral oils. This test procedure and the subsequent analysis by gel permeation chromatography show good repeatability. This test technique provides a semiquantitative measurement of evaporation, oxidation, sludge and varnish formation, oxidation products as a function of molecular

weight, and additive response. Preliminary studies with a series of five 3C reference oils show good general correlation with microoxidation test results at 225 and 245 °C. References

[1] Cvitkovic, E. , Klaus, E. E. , and Lockwood, F. , A thin-film test for measurement of the oxidation and evaporation of ester-type lubricants, ASLE Trans., 22, [4], 395-401

(1979).

[2] Ali, A., Lockwood, F. E. , Klaus, E. E. , Duda, J. L. , and Tewksbury, E. J., The chemical degradation of ester lubricants, ASI F Trans., 22, [3], 267-76 (1979).

[3] Crumley, R. , private communications (1976).

294
National Bureau of Standards Special Publication 584. Proceedings of Joint Conference

on Measurements and Standards for Recycled Oil /Systems Performance and Durability held at

NBS, Gaithersburg, MD, October 23-26, 1979. (Issued Nov. 1980)

DETERMINATION OF POLYCHLORINATED BIPHENYLS IN WASTE

AND LUBRICATING OILS

S. N. Chesler, W. E. May, P. A. White, R. M. Parris, and F. R. Guenther

Center for Analytical Chemistry

National Bureau of Standards Washington, DC 20234 Polychlorinated biphenyls (PCBs) are noxious pollutants which occur widely in our environment. They are, in themselves, moderately toxic and have been shown to have both mutagenic and carcinogenic properties. PCB-containing fluids have found widespread use as coolants in high voltage electrical components; and as these components are discarded, PCBs are introduced into the ecosystem. Due to the multitudinous methods of used motor oil collection prior to recycling, there is a real possibility of inadvertant contamination of the collected oils by PCB-containing fluids. It thus becomes necessary to develop an ana- lytical technique to determine the presence and concentration of any PCB contaminants in waste oils. PCB fluids are not made up from one or a few different chemical species but from the

209 possible isomers of chlorinated biphenyl (fig. 1). The preceding structure shows the possible sites for chlorination on the biphenyl nucleus. PCB fluids unfortunately have most of the same physical properties as the natural components of lubricating oils which

makes it very difficult to separate out the PCB contaminants present in any oil sample.

2

2'

Figure 1. A number of procedures have been developed for PCB analysis in waste and/or lubricating

oils [1-5] 1

. These procedures, however, all suffer from the inability to adequately remove

analytical interferences from typical waste oil samples. Most are time consuming due to the many manual operations required for sample cleanup, and all employ low resolution chromatographic procedures which can make quantitative identifications difficult. In this paper, we report a method which overcomes these deficiencies. This method first employs preparative

scale high performance liquid chromatography to remove analytical interferences, and glass capillary gas chromatography to identify and quantitate any PCB contaminants in the samples

analyzed. Prior to analysis, samples are filtered and/or centrifuged to remove any extraneous

materials and water. The samples are then accurately diluted in hexane to a ratio of about

8 to 1 (hexane to sample) and are ready for the liquid chromatographic cleanup procedure.

Figures in brackets indicate the literature references at the end of this paper. 295
A small amount of the diluted sample is injected upon the liquid chromatographic column and fractionated such that the PCBs in the sample can be collected separately from polar

analytical inferences. The proper fractionation procedure is ascertained from column cali- bration by standard mixtures of pure PCBs. The details of the liquid chromatographic proce- dure used in this study are listed in table 1. The sample obtained from the cleanup proce- dure is concentrated to 50 pL under a stream of dry, filtered nitrogen gas and 0.5 pL ali- quots are analyzed by capillary gas chromatography. The average gas chromatographic analysis takes less than 45 minutes. The details of the gas chromatographic procedure are listed

in table 2. Table 1. Liquid chromatographic conditions for cleanup of PCB containing samples.

Pump: Column: Detector: Detection wavelength: Sample size: Flow rate: Mobile phase: Fraction collected:

High pressure pulseless

Prep scale aminosilane 7.9 i.d. x 30 cm Multiwavelength ultraviolet

205 nm 140 pL 4.6 mL/min

1% methylene chloride in hexane

11 to 27.5 (Tillable 2. Gas chromatographic conditions for analysis of PCBs. Column: SE-52 WC0T glass capillary, 0.3 mm i.d. x 20 m Temperature program: 200 °C for 2 min, then 2 °C/min to 275 °C Injector temperature: 300 °C Detector temperature: 300 °C Split ratio: 30:1

2 Column inlet pressure: 0.5 Kg/cm

Detector: Electron capture - constant current, Ni*^ Carrier Gas: He Sample Size: 0.5 pL Integrator: Digital

The above method was compared to the method of Takano et al. , [2] in our laboratories. The Takano method is a classical one employing solvent extraction, column chromatography,

and sulfuric acid partition, and is similar to other commonly used procedures [1,4,5]. In this comparison, two samples were analyzed: 1) the first was a virgin base oil deliberately contaminated with 10 ppm (pg/g) of Aroclor 1254 (a PCB fluid containing over 65 individual

PCB isomers with an average chlorine content of 54 percent), and 2) a waste crankcase oil also with 10 ppm Aroclor 1254 added. The complete method of Takano took over eight hours per sample with seven hours for sample cleanup and one hour for gas chromatographic analysis. The method of Takano was unable to identify the presence of Aroclor 1254 in the waste crank- case oil sample. On the other hand, the method described in this study was able to identify

and measure the Aroclor 1254 in both samples with a total analysis time of less than 70 min- utes per sample.

296
The glass capillary gas chromatographic method yields enough separation of the individual PCB isomers so that two or more different contaminating PCB fluids can be identified

and measured simultaneously. This is not possible when using the noncapillary, low resolu- tion gas chromatographic procedures in the other methods [1,2,4,5].

The quantitative determination of PCB mixtures in lubricating oils can best be carried

out by standard addition techniques because of the large variances in the electron capture

response factors of the individual PCBs. Further, if more than one PCB fluid is found as a contaminant in the sample, a matrix algebra technique such as that proposed by Eder [6] must

be employed to determine the ratio of the individual fluids. This method requires both tedious calibration with accurately known PCB mixtures and sophisticated data acquisition

and reduction instrumentation.

In conclusion, we feel that we have devised a useful, quick, and accurate method for determining PCBs in lubricating and/or waste oils and that this method is superior to any existing methods. References

[1] Bauer, U. , Vom Wasser , 38, 49-62 (1971).

[2] Takano, N. , Nakano, T. , Takeshita, K. , and Sekiyu, Gakki Shi , 17, 159-161 (1974).

[3] Balliardo, F. , Gionchiqlia, E. , and Nano, G. M. , J. Liq. Chromato. , 2, 77-83 (1979).

[4] Osborne, J., unpublished method.

[5] Phillips Petroleum Company, Method 7837-AG, Issued 6 Nov 1978.

[6] Eder, G. , J. Chromato., 121, 269-277 (1976).

29 7

Session 7 SYSTEM PERFORMANCE AND DURABILITY

299

National Bureau of Standards Special Publication 584. Proceedings of Joint Conference

on Measurements and Standards for Recycled Oil/Systems Performance and Durability held at

NBS, Gaithersburg, MD, October 23-26, 1979. (Issued Nov. 1980)

LUBRICANT FACTORS IN ROLLING CONTACT FATIGUE

C. N. Rowe

Mobil Research and Development Corporation

Central Research Division

Box 1025 Princeton, NJ 08540

1. Introduction

Although the fatigue failure of bearings and gears has been a well known phenomenon for some time, it is only relatively recent that researchers have recognized that lubricant

physical and chemical properties can influence fatigue life. This new appreciation of the role of lubricant factors is due primarily to three advances in technology.

First, the use of cleaner steels with fewer imperfections in the machined components had the result of eliminating many of the early subsurface initiated microcracks, thereby not only resulting in longer fatigue life but narrowing the distribution of the fatigue lives. Shifting the point of crack initiation from subsurface to surface and increasing the fatigue

life not only make it possible for chemical factors to come into play to a larger degree, but

to be recognized.

Second, improvements in bearing design, surface finish, and cleaner lubricant systems decrease the chance of asperity interactions at a constant EHL film thickness. Particles of hard debris of similar size or larger than the EHL film thickness upon going through the contact zone act as stress raisers on the surfaces which can initiate surface microcracks.

The third, and probably the most significant advance, is the current development of the understanding of the role of elastonydrodynamic lubrication (EHL) film thickness and lubricant viscosity on fatigue. The EHL film thickness of the interposed lubricant in a rolling or combined rolling/sliding contact determines to what extent the high spots, or asperities, on opposing surfaces come into contact. These contacts undergo very high cyclic

stresses which serve to initiate microcracks at the surface, which are the precursors to bearing failure. This also led to the knowledge that the specific film thickness, which is the ratio of EHL film thickness to a surface roughness parameter, is a critical factor. In comparing the effects of lubricant chemistry on fatigue life it is important to make the comparison at similar values of the specific film thickness. Many machine designers and bearing manufacturers are now using the specific film thickness factor in estimating bearing

life.

2. Microcrack Formation-Spal 1 ing

All fatigue failures begin with the initiation of microcracks at the surface or sub- surface. Following initiation, crack propagation, caused by the cyclic stressing, leads to a growing network of crack damage which eventually results in metal particles spalling from the

sJrface. The fatigue spalls provide paths for lubricant to escape from the contact. This decrease in the EHL film thickness leads to metal-metal contact, metallic wear, and catastrophic surface distress followed by possible components failure. Because of the large amount of surface distress, the cause--fatigue--in a postmortem analysis is very frequently

overlooked. Figure 1 consists of four photomicrographs at 80X showing an actual failure progression in a test rig. The top photo shows surface microcracks. The second photo shows

an advancement of the initial microcrack to a small spall, while the third shows further development of cracks and more small spalls. Finally, the bottom photo shows a relatively

large spall and the bearing is on its journey to failure. Figures in brackets indicate the literature references at the end of this paper.

301
gure 1. Fatigue crack propagation (80X).

302
3. Specific Film Thickness Way [l] 1 had proposed in 1935 that the lubricant under pressure enters a surface microcrack followed by sealing of the crack in the contact zone so that the developed

hydraulic pressure causes propagation of the crack. The amount of lubricant penetrating the crack would decrease with increasing viscosity. Although this mechanism was favored for some

time, it has since been replaced by the mechanism of shear stresses at the surfaces and their

dependence on lubricant EHL film thickness. With thick lubricant films the surface asperities are sufficiently separated so that the stresses between opposing asperities will

be relatively low. Under thin film conditions, the asperities can penetrate the film and the resultant high contact stresses initiate crack formation and cause crack propagation. The viscosity of the lubricant in the entrance region of the contact determines the EHL film thickness while the viscosity of the lubricant in the contact zone affects the shear stress

level

.

Figure 2 shows, schematically, the contact area between a ball and the inner race of a deep groove ball bearing. Although the point-to-point thickness fluctuates, the separation

between the mean planes of the two surfaces defines an average film thickness, h. Two film-surface geometries having the same average thickness, h, but radically different surface roughnesses can provide a situation where the relatively smooth surfaces are completely

separated while asperities on the rough surfaces are in contact. In recent years, a quantity

called the specific film thickness, A, has been introduced to describe the lubricant film

geometry. A is the ratio of the oil film thickness, h, to the composite surface roughness,

a, where a = (a x 2 +a2

2 )^ and a x and a2 are RMS roughness values of the two surfaces.

Figure 2. Schematic of contact area between ball and inner race. Figure 3 shows relative fatigue life as a function of A. from two separate investigations; the dashed line is a composite of the two continuous curves and is the recommended curve in the ASME Engineering Design Guide for Bearings [2]. When A is below 2 the fatigue life is greatly reduced. 303
The evidence is convincing that specific film thickness is a critical factor in the fatigue life of bearings and gears. The EHL film thickness is proportional to the viscosity

and pressure-viscosity coefficient, both to the exponent of about 0.74. In comparing fatigue

life results from research bench tests or full scale bearings it is important to know the EHL film thickness and composite roughness so that observed differences among lubricants can be related either to variation in A or to lubricant chemical factors.

4. Fatigue Test Methods

Mobil has been using four bench fatigue testers to investigate the influence of lubricant chemistry factors on fatigue life. These are: rotati ng-beam fatigue tester [3], rolling 4-ball fatigue tester [4], uni steel bearing fatigue machine [4], and GE rolling contact fatigue rig [5]. Description and operating conditions for the testers can be found

in the indicated references. 3.5 _ SKURKA

0.6 1.0 2.0 4 6 8 10 SPECIFIC FILM THICKNESS, X

Figure 3. Relative life versus specific film thickness (ref. [2]).

5. Water-Accelerated Fatigue

The reduction of bearing fatigue life by small amounts of water in lubricants is a well known phenomenon. Cantley [6] reported the data in table 1 for the addition of water to an R&O type SAE-20 mineral oil on the fatigue life of tapered roller bearings. Increasing the water content from 100 to 400 ppm reduced the fatigue life by 48 percent. Table 1. Effect of Water in R&O SAE 20 Oil. Tapered Roller Bearings Cantley [6] Water Content

ppm Normalized to 100 ppm

25 2.6

100 1.0 400 0.52

304
Felson, et al . [7], determined the fatigue life of thrust loaded angular contact ball bearings with seven commercial mineral oil hydraulic fluids and determined the amount of water in the oils as received. Figure 4 shows my plot of their L 10 and L 50 life/specific

film thickness ratios against concentration of water inherently present in the oils. Six of the seven oils show a clear reduction in life with increase in water concentration. Increasing the water content from 100 to 400 ppm decreased the L 50 life 47 percent, in agreement

with the 48 percent found by Cantley.

500

0.005 0.01 0.05 0.1 WATER CONTENT,

%

Figure 4. Effect of inherent water content in a series of hydraulic oils

on fatigue life normalized to specific film thickness (data taken from

ref. [7]). Figure 5 shows S/N plots from the rotating beam fatigue test for dry SAE 20 minteral oil

(=; 50 ppm H 2 0) and mineral oil with 0.05 percent added water [4]. Water reduced the endurance limit by 43 percent and the fatigue lives above the endurance limit by 60 percent,

showing that the test is highly sensitive to water. Figure 6 shows the effect of water on a new formulated turbine/circulating oil containing an antifatigue additive (curve 2). Also

shown are the results for the new oil without the antifatigue additive (curve 3) and without

rust inhibitor (curve 4). These results are tabulated in table 2. Removing the antifatigue

additive from the fully formulated oil has a greater deleterious effect than removing the rust inhibitor.

305
Table 2 also shows the performance of these oils in the rolling four-ball test under wet conditions at 7.52 GPa (1.09 x 106 psi) and a A. value of 1.5. Addition of 0.5 percent water

reduces the fatigue life of the base oil from 698 000 to 580 000 stress cycles. The wet

fully formulated oil and the wet oil without rust inhibitor are as good or better than the

dry base oil. The wet formulated oil without the antifatigue additive is definitively

inferior, showing that the antifatigue additive is responsible for the good result for the formulated oil. Table 3 shows confirmatory tests on the base oils and the fully formulated

oil in the unisteel rig at a stress level of 3.90 GPa (555 000 psi) and a k of 1.6. Both L 10 and L 50 are reduced by the water in the base oil and are significantly higher in the fully formulated oil under wet conditions.

Figure 5. S/N plots showing effect of 0.05 percent added water to SAE 20 base oil.

6. Additive Mechanisms for Inhibiting Water Effect Most industrial oils contain dissolved water, in the range of 50 to 500 parts per

million. In many industrial applications oils become contaminated with moisture from the operating environment. Water molecules, being extremely small in size compared to lubricant

and additive molecules, readily diffuse to the tip of microcracks.

As a microcrack propagates by cyclic stressing, the newly created surface is highly

reactive chemically. Water undergoes decomposition and the produced atomic hydrogen diffuses

into the metal ahead of the crack, causing hydrogen embrittlement. This embrittlement not only allows the crack to propagate more rapidly, but promotes crack branching. From Mobil's investigations of lubricant additives for preventing water acceleratedfatigue in the rotating beam apparatus, three mechanisms have evolved [3b]. The mechanisms

proposed are: proton neutralization, hydrophobic surface film, and water sequestration.

306
As a class of additives, amines can neutralize protons, and several amine compounds that

have a high basicity and are small in size were found to counteract the deleterious effect of water [3b]. The requirement of small molecular size allows the molecule to diffuse to the tip of the crack along with the water molecule. Isopropylaminoethanol was found to be especially effective, confirming published results for the additive in a rolling four-ball tester [8]. mo

FATIGUE LIFE, N, CYCLES

Figure 6. Comparison of S/N plots for turbine/circulating oil containing

antifatigue additive, all with 0.05 percent added water. Table 2. Rotating beam and 4-ball fatigue results on turbine/circulating oil components.

RBF (0.05% Water)

4-Ball (0.5% Water)

Lubricant

Fatigue Life @ 120 000 psi (10 3 Cycles) Endurance

Limit,

(103 psi)

L 50 (10 3 Cycles)

SAE 20 Base Oil , Dry 160 102 698

SAE 20 Base Oil 51 44 580 Fully Formulated Oil 108 101 711 Formulated Oil Minus

Rust Inhibitor

100 92 722 Formulated Oil Minus 70 94 515 Antifatigue Additive

307
Rig Table 3. Comparison of four-ball with unisteel results. Four-Ball Stress Level , Max. GPa (10

6 psi) Specific Film Thickness

7.52 (1.09)

1.5

L 50

Base Oil (SAE 10) Dry Base Oil (SAE 10) + 0.5% Water

Fully Formulated Oil + 0.5% Water (1) Confidence Levels

No. 1 > West Base Oil

No. 1 > Dry Base Oil Dry Base Oil > West Base Oil

698

580

711

3.90 (0.565)

1.6

L 50 go

6

) 27.

a 15.4

56.3

98%

92% 85%

50

2.4°

2.7 20.4

95+%

95+%

60%

SAE 20 Base Oil Hydrophobic surface film formation is the second mechanism. n-Octadecanol and an amine

salt of n-octadecanoic acid were found to be partially effective. Sequestering of water by additives in the lubricant phase to prevent its adsorption on the surface or diffusion into microcracks is a third plausible mechanism. An amine succinate type additive is believed to function by this mechanism. Since different additives exhibit different mechanisms in counteracting the deleterious effect of water, combinations of additives could show synergistic effects and this has been observed [3b]. This points to the potential benefits of a multiple additive system.

7. Effect of Antiwear Additives

The inconsistent results obtained with antiwear and EP additives suggests that the result depends on the conditions at the contacting surfaces. An additive may give a positive response

at one set of test conditions, but gives a negative response under a different set of test con- ditions. Also, in formulated oils other additives are present, so that different additive

interactions can influence how a given phosphorus or sulfur additive affects fatigue life. Operating factors which have been shown to affect the response of EP additives are given

in table 4. An apparent important factor is the specific film thickness; evidence is emerging

that EP additives can be beneficial at low A. values, but deleterious at high A values [9]. At

low \, the additive is forming a surface film and reducing the surface roughness and stresses, while at high values the additive or a reaction product is functioning by a corrosive mechanism. Wear is of interest since without an antiwear additive present the finite amount of wear

that can occur under rolling conditions can remove surface microcracks before they are able

to propagate. With the antiwear additive present, the wear is greatly reduced and the surface initiated microcracks are able to propagate. This may be one mechanism by which

antiwear additives reduce bearing life. A second mechanism is that wear leads to a more conforming contact with reduced contact stress. As a general statement, many factors can affect the nature of the response of an additive, and no real guidelines have yet emerged. 308
Table 4. Factors affecting response of extreme pressure additives,

o Specific Film Thickness

o Metallurgy

o Additive Concentration

o Additive Reactivity

o Stress Level

o Lubricant Oxidation

o Surface Films

o Wear

Kepple and Johnson [10] investigated the influence of rear axle lubricants on tapered

roller bearings at 1.03 GPa (150 000 psi) Hertz stress, and the L 50 results in table 5 are normalized to a premium rust and oxidation inhibited oil. The comparison shows that the additives can reduce the L 50 fatigue life to as little as 17 percent of the life with the

non-EP oil. The Weibull slopes are reasonably close except for one phosphorus-sulfur

additive package in SAE 90 grade which has an unusually high slope. The EP additives, which

are required to prevent wear of the hypoid gear, may lead to a reduced fatigue life of the support bearings. This could be a future problem area if lower viscosity gear oils, which

minimize frictional losses and increase fuel economy, are used. Table 5. Effect of rear axle lubricants on fatigue life

of tapered roller bearings. Kepple and Johnson [10] 1.03 GPa (150 000 psi) Maximum Hertz Stress Grade

Type of

EP Additive Package

i-50 Life, Normal ized Weibull Slope

90 None 1.00 1.45

80 Lead-Sulfur 0.24 2.63

80 Lead-Sulfur 0.34 1.26

80 Phosphorus-Sulfur 0.32 1.71

90 Zinc- Phosphorus-Sulfur 0.17 2.37

90 Zi nc-Phosphorus-Sul fur-Chl ori ne 0.40 2.27

90 Phosphorus-Sul fur 0.67 7.69

8. Organic Phosphonate Additive

A good example of a novel mechanism by which additive chemistry influences rolling

contact fatigue is that of an organo phosphonate additive [11]. This compound cannot be used

as an anti fatigue component in many formulations because of the interference with other

performance properties. Figure 7 illustrates the influence of the additive in a mineral oil on the GE Rolling Contact Rig. It was found that the life improved with time, indicating a 309
Figure 7. Effect of the organic phosphonate additive in an SAE 20 mineral oil. build-up film on the surface of the rollers, which are not changed between tests. Electron probe analysis of the film showed that phosphorus was present and x-ray diffraction showed

the film to be amorphous.

An optical EHL rig was operated for a period of time at 99 °C and it was found that the rolling speed required for a constant film thickness decreased with time. Calculating the generated EHL film thickness at each rolling speed and subtracting from the total film thickness, the chemical film thickness was obtained as a function of time and the results are

in figure 8. This is direct evidence, using a novel technique, that this additive forms a surface film in a concentrated contact. These experiments demonstrate that the organic phosphonate can generate a thick chemical film within a rolling EHD contact. The rate of deposition is temperature dependent. The produced film can prolong fatigue life by one or more of the following mechanisms: 1) increasing the effective film thickness; 2) reducing apparent surface roughness; 3) inhibiting ingestion of oil into the crack, and; 4) reducing traction which will minimize tangential stresses and crack initiation and crack propagation.

9. Summary

In summary, we are in a learning phase on the role of lubricant and additive chemistry

on the fatigue life of bearings. Much more work is needed to establish guidelines as to what

type additives are detrimental and what type additives are beneficial. On the latter, work

is needed to define the size of the increases to be expected. In all probability, gains in fatigue life will be seized upon by designers to operate bearings under more severe conditions.

310
140

0 10 20 30 40 50 60 70

TIME, MINUTES

Figure 8. Growth of the chemical film thickness with time. References

[1] Way, S. , Pitting due to rolling contact, Trans., ASME, 57, A49 (1935).

[2] Life Adjustment Factors for Ball and Roller Bearings —An Engineering Guide, sponsored by the Rolling-Elements Committee, The Lubrication Division of the ASME (1971).

[3] Polk, C. J., Murphy, W. R. , and Rowe, C. N. , Determining fatigue crack propagation rates

in lubricating environments through the application of a fracture mechanism technique,

ASLE Trans., 18, 290 (1975); Murphy, W. R. , Polk, C. J., and Rowe, C. N. , Effect of Lubricant Additives on Water-Accelerated Fatigue, ASLE Trans. , 21, 63 (1978).

[4] Armstrong, E. L. , Leonardi , S. J., Murphy, W. R. , and Wooding, P. S. , Evaluation of water-accelerated bearing fatigue in oi 1 -1 ubricated ball bearings, Lub. Engr. , 34, 15 (1978).

[5] Murphy, W. R. , Armstrong, E. L. , and Wooding, P. S. , Lubricant performance testing for water-accelerated bearing fatigue, Roll ing Contact Fatigue Performance Testing of Lubricants , chap. 16, E. Tourret, and E. P. Wright, eds. (Heyden & Son Ltd., London,

1977).

[6] Cantley, R. E. , The effect of water in lubricating oil on bearing fatigue life, ASLE

Trans. , 20, 244 (1977).

[7] Felsen, I. M. , McQuaid, R. W. , and Marzani, J. A., Effect of sea-water on the fatigue

life and failure distribution of flood-lubricated angular-contact ball bearings, ASLE

Trans. , 15, 8 (1972).

[8] Schatzberg, P., Inhibition of water- accelerated rolling contact fatigue, J. Lub. Technol. , 93, 231 (1971).
[9] Quinn, F. J. and Philips, M. R. , The effect of surface roughness and lubricant film thickness upon contact fatigue, Conf. on Effects of Surface Roughness in Lubrication, Tribology International, 10, 331 (1977) (Lyon, France, Sept. 13-16, 1977). [10] Kepple, R. K. and Johnson, M. F. , Effect of Rear Axle Lubricants on the Fatigue Life of Tapered Roller Bearings, SAE Paper No. 760329 (1976).

[11] Fowles, P. E. , Jackson, A., and Murphy, W. R. , Lubricant Chemistry in Rolling Contact Fatigue--The Performance and Mechanism of One Anti fatigue Additive, ASLE Paper 79-LC-4A-1, ASLE/ASME Lubrication Conference , Dayton, Ohio (October 16-18, 1979).
National Bureau of Standards Special Publication 584. Proceedings of Joint Conference

on Measurements and Standards for Recycled Oil /Systems Performance and Durability held at NBS, Gaithersburg, MD, October 23-26, 1979. (Issued Nov. 1980)

THE RELATIONSHIP BETWEEN VISCOMETRIC LABORATORY MEASUREMENTS AND FIELD PERFORMANCE AND SERVICE Theodore W. Selby

Savant, Inc. 234 East Larkin

Midland, MI 48640

1. Introduction

It has been long known that viscosity is the heart of hydrodynamic lubrication. Stribeck's curve is a rather explicit statement of this relationship for a journal bearing. This curve is shown in figure 1 where the coefficient of friction is plotted against a parameter qN/P where q is the viscosity, N is the journal speed and P is the load on the

journal. The straight-line portion of the curve represents the range of hydrodynamic

lubrication controlled by the viscosity while the mixed lubrication and boundary lubrication

regions are also indicated. All of this work in developing the information which ultimately

reduced to the Stribeck curve (and other relationships) between viscosity and lubrication,

was with Newtonian fluids in which the shear stress is proportional to the shear rate with

the constant of proportionality defined as the viscosity by Newton. V\ % //

\ V- Mixed

F

c

n n/p

Figure 1. Stribeck curve. For coaxial cylinders: 1 = f[qN] and for the bearing equivalent: (from Stribeck) F c = f[qN/P]; f[ ] indicates a function;

T is torque; N is speed; q is viscosity; F c is the friction; and P is pressure.

In the middle 40' s and early 50' s it was found possible to improve the range of refined

basestocks capable of making suitable engine oils by adding small quantities of certain

oil-soluble polymers called Viscosity Index Improvers. These polymeric additives brought

about a profound change in lubricant technology. They also brought about a long period of confusion, new questions regarding the process of lubrication and new understandings regarding the role of such polymers in lubrication. That period is certainly not over yet; we are

still seeking to understand the viscometric behavior of oil-soluble macromolecules in the engine as will be hopefully gathered from the following paper.
Other lubrication needs and problems came into focus over the last 20 years and it will also be one of the objects of this paper to discuss how the viscosity of the lubricant controls these other relationships important to field performance and service.

2. The Effect of VI Improvers on Automotive Lubrication--

A Recent History

As previously indicated, VI Improvers were brought into the commercial world in an effort to improve the viscosity-temperature characteristics of refined basestocks and the term "multi-grade" entered into our jargon. Up to and beyond the time they were introduced

it was the practice to determine the kinematic viscosity of an engine oil at 100 and 210 °F and to extrapolate these viscosities to either higher or lower temperatures using the Walther

equation or ASTM Viscosity-Temperature Charts derived from the Walther equation as in figure

2. (It had been found over the years that the Walther relationship was relatively accurate

for most extrapolations concerned with mineral oils.) When this extrapolation technique was used with polymer-modified oils an anomaly occurred: the extrapolated viscosity of the polymer-modified at low temperatures (e.g. 0 °F) was found to be lower than that of the base

oil used, as shown in figure 3. Despite their enthusiasm, it was very hard for experi- mentalists in those days to accept the fact that a formulated lubricant could somehow be less viscous than the base after a very viscous VI Improver was added. This apparent crossover of figure 3 caused by extrapolation was brought to measurement at the bench early in the 1950'

s

and it was shown (fig. 4) that the crossover was an illusion of hope brought about by assuming that the extrapolation technique was appropriate. There was a crossover, but it occurred at a lower temperature where gelation affected the kinematic results.

\ ^cros sover?

base oil

+

base > oil

TEMPERATURE " Figure 2. Extrapolated method of determining

0 °F viscosity. Figure 3. Comparison of extrapolation values

of base stock and base stock plus polymer. However, even this information was not entirely suitable nor sound since the measurements were still made by kinematic capillary viscometers, that is, at low shear stresses. Some of the automotive engineers and lubricant specialists from the petroleum industry claimed that since engine cranking speed was important to starting, the true measurement of response to the engine oil viscosity should first be made with the cranking engine and then extended to a suitable viscometer if, indeed, the low temperature viscosity classification

system was to have significance in regard to engine starting at low temperature. So began a series of cranking experiments with the automotive engi ne--ef forts which went on in various laboratories for about 15 years. In the process of this work, higher and higher shear stress viscometers were brought to bear on the problem to attempt to develop correlation with the information being generated by cranking engines on a number of reference engine oils. Finally, in the middle 60's the ASTM's RDD-7, which had been conducting a large part of these

tests in cooperation with the CRC, finally obtained sufficient information on various viscometers to indicate that an instrument newly developed precisely for the purpose, called

the Cold-Cranking Simulator (CCS), had the highest degree of precision and was the easiest of the instruments tested to use. Most important, its correlation with engine cranking data was

also very good as shown in figure 5a at 0 °F and figure 5b at -20 °F. 314
Figure 4. Extrapolated viscosity error in the comparison of a multi grade oil to its base stock.

TEMPERATURE *F (Los Sca\»)

A. B.

13 -LAB COLO-CRANKING |4 . LAB COLD - CRANKING

SIMULATOR VISCOSITY, POISES SIMULATOR VISCOSITY, POISES

Figure 5. Correlation of the cold-cranking simulator with engine cranking speed. However, this portion of the story is not over. Very recently, because of a new round of studies aimed at further developing the SAE Viscosity Classification System, it has been proposed that the CCS be used over a relatively broad temperature range, from 0 to -40 °C. Preliminary information from the field indicates that the CCS still correlates quite well with the cranking speed of gasoline engines.

As a fillip to the story: It is interesting that, in the middle 60' s, work was done

showing the cranking speed of a gasoline-fired engine was an effect of viscosity and not, as previously assumed, particularly important to the starting of the engine. However, the same

study showed that viscosity was directly very important to the starting of the engine

presumably because it was the engine oil viscosity which had to be overcome by the starting

(i.e. low-speed) torque of the engine. Fortunately, the fact that the Cold-Cranking

Simulator had already been developed to correlate with engine cranking speed turned out to be

an acceptable relationship since the cranking speed was, after all, a measure of the viscosity experienced by the engine.

315
2.1. High temperature studies

In the meantime, questions were being asked about the high temperature performance of Viscosity Index improved oils. Although the presence of a VI Improver in the oil contributed

a considerable amount of kinematic viscosity to the basestock when the oil was new, after a certain period of use some of this viscosity contribution of the polymer seemed to be lost. This was called, appropriately, "permanent viscosity loss" (PVL). The question that developed was whether an oil experiencing such permanent viscosity loss would continue to provide sufficient lubrication to the bearings and pistons of the engine. In 1967, ASTM's

RDD-7 began a study to test whether a bench test could be found to correlate with engine

tests regarding the degree of PVL. Accordingly, reference fluids were established and

several small fleets of cars were run on these fluids in the United States as well as in Europe. It was found, however, that the complex physical and chemical degradation of the VI Improver which took place in the engine could not be totally reproduced with tests based solely on mechanical degradation. Of the results obtained, one of the best was the correlation between the engine tests and the diesel injector, as shown in figure 6. The exceptions were two polymer types, one of which reassociates after shear (ARO-109) and one of which was quite susceptible to oxidation (ARO-106). Work continues on the study of test methods and a diesel injector test method is presently being balloted in the ASTM. In the meantime, regarding the original concern about the lubricating function served by VI Improvers

in the engine, other work on determining the viscosity of the engine oil in the bearing was already underway.

0 12 3 4 5

Diesel Injector Viscosity Loss, cSt, 5> 210 F

Figure 6. Correlation between the best diesel injector test data and the six-fleet

average.

316
2.2. Bearing viscosity

As previously mentioned, with the advent of multi grade engine oils, experimentalists in bearing lubrication were concerned that temporary and/or permanent viscosity loss would or could be reflected in increased bearing wear. Bearing test rig studies over the last 10 to

20 years by DeHart, Rosenberg, and others showed that polymer-modified fluids always gave

less friction in the bearings than would be predicted on the basis of extrapolated viscosity

at bearing operating temperature. One example is shown from work by Rosenberg in figure 7. This figure is interpreted as a section of a Stribeck curve as shown and it is quite evident

that none of the polymer-modified engine oils are on the curve established by the Newtonian

oils. These observations were interpreted to mean that: 1) low shear stress (kinematic) viscosities were not relevant to the bearing, 2) energy losses to polymer-modified multigrade

engine oils were less than their single-grade counterparts, and 3) oil film thicknesses

should be less in the bearings. Therefore, Rosenberg measured oil film thickness in the bearing

for the results of the above-mentioned study and found that these were, as expected, less than predicted from low shear stress viscosities at the bearing temperature, as shown in figure 8. However, Rosenberg also noted that there is a major difference between bearing test rigs such

as his own and the bearing in a fired engine. The latter not only applies inertial loads but time-varying gas loads to the bearing. Thus, he noted a real possibility that viscoelastic

effects contributed by the polymers might offer further bearing wear protection than simple

viscous effects.

AVERAGE SOMMERFELD NUMBER Figure 8. Film thickness of VI improved oils compared to base oil performance.

317
Subsequently, road tests reported by Stambaugh, Kopko and Bennett showed that some polymer-modified fluids made with highly shear-susceptible VI Improvers were less than adequate to protect the bearings from catastrophic failure while other, less shear- susceptible, polymers were quite adequate. Specifically, figure 9 taken from some of their

work, shows that a minimum viscosity SAE 20w-20 oil did not protect the main bearings of the engine during 50 000 miles of severe service (police "chase" cars). Use of shear-susceptible

VI Improver E gave little more protection whereas shear-stable VI Improvers B and D gave quite acceptable bearing protection. As a consequence of their studies, Stambaugh and Kopko indicated that, in larger, American-made engines such as those used in their studies, a critical viscosity of about 3.3 to 3.8 cSt would be expected.

Figure 9. Illustration of main bearings and the effects of shear-susceptible VI improvers with severe service conditions. Very recently, studies by McMillan and Rosenberg showed that even in long duration driving tests under milder but still onerous, test conditions, there was a distinct difference between shear-susceptible VI Improvers and relatively shear-stable VI Improvers.

In their work, they made a head-to-head evaluation of four VI Improvers in a common basestock/additi ve-package through a constant high-speed (75 MPH), high-temperture (300 °F),

50 000 mile proving ground test. Two of the VI Improvers were from one family of polymers

318
and the second two from a different family. In each pair one VI Improver was of higher molecular weight (more shear susceptible) and one of lower molecular weight (more shear

stable). Thus, the total comparison was between VI Improver families and molecular weights

of the polymers. Their studies show that: 1) more shear-susceptible VI Improvers give greater wear (figs. 10 and 11), and, somewhat surprisingly, 2) greater oil degradation (figs. 12 and 13).

Polymethacrylate Polymethacrylate Olefin-Copolymer Olefin-Copolymer

- stable - - unstable - - stable - - unstable - Figure 10. Typical rod bearings after 80 000 km of high-speed, high-temperature

service.

Figure 11. Relationship between wear and high-temperature, high-shear-rate viscosity.

VISCOSITY AT 6 X 10

5 S

_1 AND 149 °C. cSl 319
Polymethacrylate Polymethacryl ate Olefin-Copolymer Olefin-Copolymer

- stable - - unstable - - stable - - unstable - Figure 12. Rocker covers showing sludge deposits. Regarding bearing wear, McMillan and Rosenberg state that 4.5 cSt is a critical viscosity for this engine as was noted in figure 11. Viscosity values less than this level are believed to produce the bearing wear shown in figure 10. As a consequence of these studies and as the result of a number of changes that were anticipated in the SAE Engine Oil Viscosity Classification System, the SAE requested ASTM's RDD-7 to develop a high shear viscometer test for engine oils. RDD-7 initiated this work about a year and a half ago and

has enjoyed the cooperation of the European CEC as well.

At this point it may be instructive to contrast some engine oils from the marketplace. Very recently, and as yet unpublished, viscometric studies on the combined effects of both permanent and temporary viscosity losses on three well-known commercial 10w-40 multigrade

engine oils are shown in figure 14. The data compare the viscosities at 300 °F on the ordinate with the permanent viscosity loss on the abscissa at two shear rates (0.5 x 106 and l.OxlO 6

s -1

) for the three oils. Also indicated are the two critical viscosity levels of 4.5

(high wear studies) and 3.5 cSt (catastrophic bearing failure) indicated by the previously mentioned studies. It is apparent that choosing a shear stable VI Improver and an adequate

base stock such as was apparently done to obtain the properties of Oil 1, can prevent the engine attrition expected from Oils 2 and 3 when, and as, they fall into the critical viscosity zone shown by McMillan and Rosenberg's work. A reasonable conclusion from this data is that permanent and temporary viscosity losses can be very important to the life span of the engine, and thus, the selection of properly shear stable VI Improvers is a desirable adjunct to the manufacturer of quality engine oils.

320
Polymethacrylate

- stable - Polymethacrylate

- unstable - Olefin-Copolymer

- stable - Olefin-Copolymer

- unstable -

o

I 1\

Figure 13. Oil pump inlet screens showing amount of screen plugging.

o Oil #2

" Oil #3

- — o oil #2

-a Oil #3

"•"(^OOO miles) - ' FISST Results, Number of Passes

Figure 14. Comparison of three commercial 10w-40 motor oils before and after shear degradation in the fuel injector shear stability test (FISST). (Comparison made

at two high shear rates.)
2.3. Beyond Stribeck

In the time since the oil embargo of 1973, and particularly with the rapid increase in

oil prices, the question of improving the fuel efficiency of the engine oils has been raised. As a consequence, the further question has been raised about the role of viscous friction as

a source of energy loss in the engine. That is, the same viscosity which provides hydro- dynamic lubrication is also an energy sink regarding its frictional characteristics.

As previously mentioned, the Stribeck curve has long been used as an index of the relationship between viscosity and the coefficient of friction in an engine. However, the Stribeck curve of figure 1 applies to journal bearings. In the automotive engine the major

source of friction (60-80 percent) is in the piston/cylinder interface as shown in figure 15 and this area must be treated as a slider bearing. For the piston/cylinder interface, the literature shows that the Stribeck curve of figure 1 no longer applies. Instead of the coefficient of friction, F , being proportional to r\H/P and the curve now appears as in figure 16. Since from 60 to 80 percent of the frictional energy expended by the engine

occurs in the piston-ring/cyl inder-wal 1 interface area, in which friction is affected by only

the square root of the viscosity, it is evident that decreasing the viscosity in order to gain some benefit of reduced friction will be of relatively limited benefit to fuel economy. On the other hand, such a reduction in the viscosity may very well create a condition of greater bearing vulnerability under particularly severe engine operation. In other words, on the basis of the way in which the engine absorbs energy through viscosity not much can be gained by reducing viscosity but much can be lost. Recent experiments on the reduction of friction by reducing viscosity seem to confirm this speculation—that is, little benefit in fuel economy was found.

1 i i K

\

rod .J

I i i

rings

miles per hour

Figure 15. Percent distribution of rubbing friction. (Typical engine at road

load.

)
If, then, some effective improvement in fuel efficiency of engine oils is to be made, perhaps the role of friction modifiers might be the most appropriate direction in which to

1 go. This has been shown to be the case with certain soluble and colloidal friction modifiers.

Moreover, the evidence intimates that the bottom of the Stribeck curve might be effectively

extended by a friction modifier as has been suggested by McDonnell and Tempe, and Ghirla and

Smith (fig. 17). This leads to the question of whether the engine can operate efficiently

and with control of the bearing wear by the use of friction modifiers coupled with low viscosity fluids. Such experiments are presently being conducted.

2.4. Other viscosity effects of the engine oil Within the last eight years another engine oil viscosity-related problem has become

visible. This is in regard to engine oil pumpability. Engine oil pumpability is a low- temperature phenomenon related to how adequately the oil pump can supply the lubricant to the

engine. While there have been questions raised concerning engine oil pumpability for many

years, the questions did not receive the support of a problem until relatively recently in Canada a certain otherwise highly qualified oil began to cause bearing failures during the

winter. It was found that this oil and others had the tendency to form a gel at low temperatures. Consequently, the oils were removed from the market. However, the automotive industry took this as a serious warning that the present SAE Engine Oil Viscosity Classification

System was not adequate in protecting the engine since it did not include some means of measuring pumpability-related behavior. Accordingly, the SAE requested the ASTM's RDD-7 to develop a pumpability test. To do this, RDD-7 first established a series of sixteen reference

oils, two of which were Newtonian in character. They then mounted a series of engine and

pumping rig studies to first of all determine the nature of the problem. The engine and rig

studies were completed in 1975 and reported as ASTM DS 57. During the time of engine and pumping rig testing, a series of viscometric bench tests

were initiated using various low shear stress viscometers at low temperatures. Preliminary

results showed a fairly strong correlation between these viscometric bench tests and the re- sults from the engines. However, none of the first viscometric devices were simple to set up and/or use, and a new thrust of work was initiated to develop a relatively simple viscometer.

Moreover, it was found during the engine tests that two different forms of oil flow restriction occurred: One form was that caused by the gel structure previously mentioned. On starting

the engine, the vacuum developed by the pump caused the collapse of the gelled oil structure

immediately above the oil inlet tube and this quickly developed into a hole reaching the surface as shown in figure 19. Consequently, the pump and, thus, the engine became starved

for lubricant.

323
lower

engine

efficiency

higher boundary

journal bearings

"

piston & cylinder

hydrodynamic

higher

rubbing

friction

viscosity higher

(constant speed and bearing load)

Figure 17. Engine efficiency as affected by viscosity and friction modifiers. to engine

oil pump

Figure 18. Air-binding limited pumpability.

324
to engine

oil pump

Figure 19. Flow-limited pumpabi 1 ity. RDD-7 decided that an instrument acceptable for determining pumpabi 1 ity should, if possible, be capable of measuring both modes of pump 1 imitation--air-binding and flowlimited. Several instruments were proposed and investigated by one or more laboratories. At

this time, one ASTM Test Method has already been written around an instrument called the Mini-Rotary Viscometer (MRV) shown in figure 20 which was specifically devised to serve the

purpose. The MRV has shown good correlation with the engine and rig tests in terms of the Borderline Pumping Temperature (BPT) in figure 21. (Borderline Pumping Temperature is defined as "the temperature at which the minimum gallery pressure, at any time after one minute of test, is 20 psig [138 KPa]".) RDD-7 and private investigators are continuing the investigation of other viscometers and test methods, particularly including the Brookfield

viscometer which is widely used for other low- temperature, low-shear studies.

2.5. Used oil effects

In all of the foregoing discussion there has been very limited reference to used oil with the exception of that on permanent viscosity loss (which obviously is a used oil phenomenon). However, there are many ways in which the oil in the operating engine can be affected by its environment and, in turn, affect the engine creating a cycle of oil and

engine deterioration. Some short observations are in order for an area of research which has

I really not been given great attention.

2.5.1. Fuel dilution

Fuel dilution will normally cause a reduction in viscosity which, in turn, may become

harmful at high temperatures if the viscosity is reduced below the critical limit. However,

and surprisingly, fuel dilution can also be deleterious at low temperatures for another

reason. In diesel engines, the fuel oil may be somewhat waxy in nature. When mixed with the

engine oil the wax contribution may cause an increase in the Borderline Pumpability

Temperature, rather than a reduction, because of an increase in the yield stress even though

the viscosity itself is reduced. This effect is diagrammed in figure 22.

325
Thermometer

\

Co ld-Well I [Threads Wound]

Around Spindles I Pulley

Weights to Loaa S, ' idle

.erature Selector

temperature Proqram Control

Figure 20. Mini-rotary viscometer.

2.5.2. Oxidation

Oxidation effects are notorious for deleterious Chang,

; in t^jj-tric djjr^ ^

acteristics of an engine oil. In fact, v c ^metric meas temperatures are detect incipient oxidation. However s ^SfSSeJaSS possible to the engine or even more dramatic and as a consequence the parting ^mpera V the oxidation of XS^^^Tl^^XZ WpossiMe to the critical bearing areas. 32 6
O FLOW LIMITED

AIR BINDING

Figure 21. Correlation of MRV to average

engine BPT.

MRV predicted BPT, °C

Figure 22. Effects of waxy fuel dilution on gelation of engine oil. 2.5.3. Particulates

Particulates in the engine oil come from several sources, some external to the engine

and some produced by the oxidative and thermal decomposition of the oil in the operating

engine. According to one of Einstein's lesser known equations and by the results of con- siderable viscometric studies, it can be stated that all particulates increase the engine oil viscosity in proportion to a function of their concentration. The increase is not inconsequential and may, in some cases, produce a many-fold increase in viscosity. Such increases

in viscosity can deny the engine adequate lubrication.

Some of these particulates are prone to cause engine wear such as silicates and, perhaps, diesel soot, while others, such as the colloidal friction modifiers, prevent wear.

It is an interesting question as to the consequences of a mixture of wear-reducing and wear-producing particulates in the engine oil.

327
2.5.4. Volatility

One of the more obvious effects on the viscometric characteristics of engine oil is that

of the volatilization of the basestock. Basestocks are usually chosen to be of sufficiently

low viscosity to preserve the low temperature startability of the engine. However, such lower viscosity basestocks are by nature more volatile and in engine operations some of these volatile components are lost. This results in an increase in low temperature viscosity

affecting both starting and pumpability of the engine oil.

3. Conclusions Viscosity is an essential characteristic and property of the engine oil in its lubricating properties. As hopefully shown, the engine oil's viscosity has many facets and enters into many considerations connected with the protection of the engine from wear. Viscosity is also a source of energy expenditure by the engine. Taking all of this into account, it seems very important that we should maintain the effort to more closely relate

the viscous properties of the engine oil to the performance of that oil in the operating

engine. This is particularly true in the area of high shear viscometry which is directly

related to the hydrodynamic performance of the engine's journal bearings. On the other hand

it is also obvious that the proper utilization of friction modifiers may conceivably extend

the range of protection where hydrodynamic lubrication is no longer sufficient. It seems obvious that we still have much to learn about the lubricating process even at such an ap- parently simple level as viscosity.

328
National Bureau of Standards Special Publication 584. Proceedings of Joint Conference

on Measurements and Standards for Recycled Oil /Systems Performance and Durability held at

NBS, Gaithersburg, MD 5 October 23-26, 1979. (Issued Nov. 1980)

SYSTEM HEALTH MONITORING THROUGH WEAR PARTICLE ANALYSIS

P. B. Senholzi Mechanical Technology Inc. /Marine Systems 1656 Homewood Landing Road Annapolis, MD 21401

1. Introduction

Mechanical system reliability and life are a function of both structural integrity and wear integrity. Emphasis to date, has been placed on structural integrity with a "throw away" philosophy accommodating the consequences of wear integrity. Recent resource limitations

however, have promoted substantial interest into the area of equipment wear integrity optimization. The optimization process is approached from the aspects of wear prevention and wear

control. Wear prevention occurs primarily in the equipment design process while wear control

is instituted in the operational arena. Wear particle technology is a relatively recent development in the equipment wear

field. This technology utilizes the analysis of wear debris as a nondestructive reflection

of the wear condition of the respective monitored process. It is currently establishing

itself as a valuable tool in both the wear prevention and wear control arenas.

2. Technology Description

Wear particle analysis technology is based on the premise that debris generated during

a wear process can serve to reflect surface conditions present in the respective process.

As a result, the analysis of wear debris can be utilized as a nondestructive indicator of system/process surface wear condition. In the case of lubricated components, this debris is picked up and carried by the lubricant thus wear particle analysis is sometimes referred to

as oil analysis. Based on test performed under the Department of Defense Oil Analysis Program, four critical wear debris characteristics have been identified as reflecting surface wear conditions.

These characteristics are debris quantity, size distribution, composition, and morphology.

2.1. Debris quantity

Systems containing interacting components in relative motion will exhibit wear throughout their lives. The rate of system wear is affected by such aspects as operating parameters, operating environment, and the respective system surface wear conditions. By monitoring the changes in total wear debris in a system, one can assess the wear rate of a system. This total debris quantity monitoring can thus serve to reflect system operating parameters,

operating environment, and surface wear conditions. In the case of oil lubricated systems,

wear abnormalities will result in an increase in total oil borne wear debris. As an example,

total debris quantity increased during testing of oil lubricated ball bearings containing

fatigue spalls by a factor of 3-7 over that quantity exhibited during a normal wear condition.

2.2. Debris size distribution

As a system wears, a certain characteristic size distribution of wear debris is generated. The presence of system wear abnormalities will result in the generation of relatively

large wear debris particles. These abnormalities will, in turn, cause a detectable shift in the size distribution of total wear debris. This shift in debris distribution can thus be utilized as an indicator of the severity of wear in a system. The greater the portion of

large debris particles, the more severe the wear situation.

329
2.3. Debris composition

A wearing system is usually composed of more than one wearing component. In the case

of complicated systems, the wear components can number well over one hundred. These com- ponents are manufactured from a variety of materials, thus debris generated in a system is composed of numerous material types. By determining the composition of the wear debris, the source of the debris can be clarified. For example, selective debris elemental analysis of large wear particles will provide information as to what component is exhibiting an abnormal wear condition.

2.4. Debris morphology

The last and possibly the most unique wear particle characteristic, is particle morph- ology or particle shape. It has been determined experimentally, that particle morphology

can be related to the wearing component, the wear condition present, and the wear severity.

A certain particular component operating in a certain wear mode will produce a unique sig- nature with respect to the shape of the wear debris that is generated. For example, it has been determined that spherical particles present in oil lubricated systems, have been related to the presence of rolling contact fatigue within the respective monitored system. This wear debris parameter is the most difficult to monitor and relies heavily on inter- pretation due to its qualitative nature. By monitoring the above four parameters, wear particle analysis technology can pro- vide information as to system wear rate, wear severity, wear components, and active wear

modes as shown in figure 1. In the analysis process, it is impossible to assign quanti- tative assessment criteria for each parameter, for every system. As alluded to above, analysis determinations have to be based on a comparison criteria. Parameter readings must be compared with "normal" readings for a particular system. An effective implementation method is the trending of each parameter. Trending will reflect pertinent shifts in parameter readings thus, reflecting a system wear abnormality. Wear parameters Wear rate Wear severity Wear source Wear type Quantity XX X Distribution X Composition X X Morphology

Figure 1. Critical wear particleXXX analysis parameters.

3. Applications

As mentioned in the introductory paragraphs of this discussion, a systematic attack on the problem of machinery wear involves both wear prevention and wear control. Wear prevention is implemented by optimizing the wear resistance of an equipment design. This design effort impacts such aspects as materials, lubricants, additives, tolerances, filtration, and surface finish. Wear control is concerned with the minimization of equipment wear rate

(i.e., extension of wear life). This control approach is implemented during equipment manu- facture, operation, and maintenance. Wear particle analysis technology exhibits numerous effective applications within this systematic wear attack. The five major applications of wear particle analysis are as a re- search tool, a design tool, a quality assurance tool, a trouble shooting tool, and a nealth monitoring technique.

3. 1. Research tool A prime application of wear particle analysis is utilization as a research tool in basic wear mechanism studies. Once an understanding of fundamental wear mechanisms has been achieved, optimization of equipment wear prevention will be enhanced.

330
3.2. Design tool Wear particle analysis can be applied in several different facets of the equipment de- sign process. It can be utilized to categorize different wear variables (i.e., materials,

lubricants, etc.) with respect to their relative wear rates. This categorization can be used as a guide in the selection of equipment wear variables. Wear particle analysis can also be applied in the assessment of the wear integrity of

a new equipment design. Wear design problems can be identified during breadboard or prototype design testing. The application of wear particle analysis as a design tool serves to promote equipment wear prevention.

3.3. Quality assurance tool A third application of wear particle analysis is utilization as a quality assurance

tool. This application involves the wear integrity assessment of both production and overhauled/rebuilt equipment, through wear particle analysis. Such equipment problems as misassembly, and out-of-tol erance will be addressed under this application. Quality assurance efforts focus on equipment wear control.

3.4. Trouble shooting tool Wear particle analysis can also be applied as a trouble shooting tool for field operating equipment. Recurring field wear related problems can be addressed utilizing particle

analysis as a nondestructive reflection of pertinent components wear conditions. This appli- cation involves equipment wear control.

3.5. Health monitoring technique

The last, and one of the most important, applications of wear particle analysis is utilization as an equipment health monitoring technique. By the monitoring of wear debris characteristics as a reflection of surface wear condition, one can assess the "health" of a wearing system. Debris monitoring is a powerful maintenance technique aimed at equipment

wear control. This technique is a step toward realization of the on-condition maintenance

concept. The five aforementioned applications can be utilized for oil, hydraulic fluid and grease lubricated systems. In some cases, these applications can also be utilized for dry

wear. Although these areas represent fertile areas of wear particle analysis utilization, applications are not restricted solely to those mentioned.

This following discussion will center on the application of wear particle analysis as

a wear control approach or as an equipment health monitoring technique.

4. Health Monitoring Decision Process

In order to effectively implement any health monitoring technique, a viable decision

process must be developed. The following discussion will summarize a projected wear particle analysis decision process.

4.1. Elements

The projected decision process required for wear particle analysis implementation,

consists of four elements; detection, diagnosis, prognosis, and prescription.

4.1.1. Detection

The detection elements provides a first cut or preliminary determination as to the health of a machine (i.e., is the machine wearing normally or abnormally?) If no abnormalities are detected, no further analysis is required until the next detection sampling interval. If an abnormality is suspect, the next step of the decision process is pursued.

331
4.1.2. Diagnosis

The second element or diagnosis element of the decision process, serves to further clarify the machinery wear abnormality. It provides a determination as to what machine component/components are wearing and proceeds to define what wear mode/modes are present. Based on these determinations the analysis process is transitioned to the next decision

element.

4.1.3. Prognosis

The prognosis element of the decision process serves to define the course of the machinery wear abnormality. It provides a prediction of residual life (time until failure) based on wear severity, wear component and respective wear mode. 4.1.4. Prescription

The last element of the analysis process serves to define a course of corrective

action. It provides maintenance recommendations based on residual life, wearing component,

and respective wear modes.

4.2. Parameters

Technical feasibility of this decision process relies on the ability of wear particle parameters to reflect wear abnormalities and abnormality ramifications. Based on wear particle analysis research, the following marriage of decision elements and wear particle parameters has been developed.

4.2.1. Detection

As indicated above, the purpose of the detection element is to provide an initial deter- mination as to the health of a machine. Based on technology research, abnormal wear can be effectively detected by monitoring both wear particle quantity and size distribution.

4.2.2. Diagnosis

Once an abnormality has been detected, it is the purpose of the diagnosis element to provide information as to the source and type of the respective wear abnormality. Again, based on pertinent technology research, abnormal wear condition clarification can be accom- plished by performing an elemental analysis and a morphology classification of the respec- tive wear debris.

4.2.3. Prognosis Prognosis determinations are based on the analysis and interpretation of the monitored

parameters already cited. Analysis criteria developed through knowledge, experience and parameter trending of individual equipment types, serve to drive these determinations.

4.2.4. Prescription

As in the prognosis decision element, prescription determinations are based on the analysis and interpretation of previously mentioned parameters. Analysis criteria developed

through individual equipment experience and parameter trending, also drives the prescription

determinations.

4.3. Maintenance level Implementation of the health monitoring decision process, requires the assignment of monitoring responsibility to pertinent maintenance levels. The detection decision element

should be implemented at the first line or organizational level of maintenance. Abnormal wear detection capability will be applied either in-line with respect to the equipment

lubrication system, or off-line in the general vicinity of the equipment. Determination

332
as to in-line or off-line application will be based on equipment cost and criticality

considerations. Front line assignment of the detection element serves to provide diag- nostic capability to the first line maintenance community, provides real time wear con- dition monitoring, minimizes existing sampling problems, eliminates a substantial portion

of the existing oil sampling workload (i.e., samples are only submitted when an abnormality

is detected) and will thus result in a decrease in the number of required centralized oil analysis laboratory facility. The diagnosis, prognosis and prescription decision elements should be implemented at

a centralized facility, located either at the intermediate or depot maintenance levels. These element implementations require relatively advanced analysis equipment, advanced

operator training and a developed equipment wear expertise. Assignment of these decision

elements to a centralized location will serve to promote these requirements as well as optimize facility utilization, and amortize facility costs over numerous supported operating

facilities. The total particle health monitoring decision process as described, is summarized in figure 2.

Detection

Prognosis

Prescription

Equipment

| Oil Sample)- Wear Mode/

Component

Residual

Life

Maintenance

Action

Organizational

Level

Composition/

Morphology

Quantity/

Distribution

Analysis

Criteria

Analysis

Criteria

Intermediate/

Depot Level

Figure 2. Wear particle analysis health monitoring decision process.

5. Proposed Health Monitoring Equipment

Full implementation of the health monitoring decision process requires identification

of specific wear particle analysis equipment capable of effectively monitoring the pertinent

parameters at the specified maintenance levels. Since the decision elements of prognosis

and prescription involve no required monitoring equipment, this discussion will focus on the elements of detection and diagnosis. A proposed equipment approach for these elements, is suggested in the following paragraphs.

333
5.1. Detection

Detection element analysis equipment has to be capable of monitoring wear debris quan- tity and size distribution at the first-line maintenance level. In the case of high cost and/or critical equipment, this monitoring capability would preferably be performed in-line

in the respective equipment lubricant system. A particle counter would serve to meet these requirements. This application is not as simple as it appears, however. No present particle counter has thoroughly demonstrated required operational and sensitivity capability.

5.2. Diagnosis Diagnosis element analysis equipment has to be capable of monitoring all wear debris

critical parameters; quantity, size distribution, composition, and morphology. This monitoring effort will be implemented at the intermediate or depot maintenance level. No one analysis technique will provide this total required capability, thus a combination of tech- niques need to be identified. Three types of analysis equipment, utilized collectively,

will provide necessary capability. These equipments are a particle counter, a spectrometer

and a ferrograph.

5.2.1. Particle counter

The particle counter would provide information as to wear debris quantity and size distribution and would be the laboratory equivalent of the detection unit described under

the above subparagraph. Laboratory counters are presently available which surpass neces- sary sensitivity and operational requirements dictated by this application.

5.2.2. Spectrometer Spectrometric analysis provides data as to the concentration levels of present wear

debris elements. This information would obviously apply to the wear debris analysis parameters of quantity and composition. Laboratory spectrometers are presently available which satisfy capability requirements of this application with one exception. Present instru- ments exhibit an insensitivity to the analysis of large debris particles. This insensitivity, although undesirable, does not present a major shortcoming when the spectrometer

is utilized in conjunction with the other two proposed analysis equipments.

5.2.3. Ferrograph

The ferrograph is a relatively new wear debris analysis technique. It provides a com- bination of qualitative and quantitative assessments of wear debris quantity, size distribution, composition and morphology. This technique, however, is primarily attuned to the analysis of ferrous wear debris. The exhibited attunement is a result of the magnetic sep- aration principles that are employed by ferrography. This technique is presently available

for laboratory application.

Data generated from the above three equipments is analyzed collectively. Each input serves to reinforce and/or complement the other inputs. Diagnostic decisions will be based

on this collective data analysis. A summary of the proposed equipments vs parameter capa- bility is provided in figure 3. The equipment proposed in this discussion serves to represent one approach to wear particle analysis. It is not meant to infer that these equipments cannot be substituted

for or supplemented by other types of pertinent analysis equipment. Particle parameters Quanti ty Pi stribution Composition Morphol ogy Particle counter X X Spectrometer X X Ferrograph XX XX

Figure 3. Wear particle analysis equipment capability.

334
6. Wear Debris Sampling

A critical aspect in the wear particle analysis approach is the wear debris sample. Care must be taken to ensure that the analyzed wear debris sample is representative of the

total wear debris being generated in the monitored system.

In the case of oil lubrication components, the generated wear debris is picked up by

the oil and circulated throughout the lubricant system. Sampling of oil borne wear debris

can be accomplished by either an in-line or off-line technique. In-line sampling involves the monitoring of debris parameters directly in the lubri- cation system. This approach provides a real time indication of the monitored parameters.

In order to implement this approach, the monitoring equipment must be tied directly into the monitored equipment lubricant system. In-line monitoring of wear debris quantity and size distribution parameters, is proposed for the detection health monitoring element of high cost and/or critical application machinery. In-line sampling, although simple in theory, presents several practical implementation

problems. A major portion of these problems result from the operating parameters dictated

by the direct lubrication system tie in. Such parameters as flow, pressure, and temperature,

as seen in a lubrication system, are not conducive to effective debris monitoring. Off-line sampling involves the withdrawal of a lubricant sample containing wear debris,

from a lubrication system. Samples can then be transported to a laboratory for analysis.

This approach provides more analysis versatility than the in-line sampling approach. Off-line

sampling is proposed for the diagnosis health monitoring element. This element requires parameter analysis that presently can only be practically applied in a laboratory environment. Although more versatile than the in-line approach, off-line sampling is very dependent

on sampling technique. Such factors as sampling interval, time after shutdown, and sampling

location can drastically effect sample wear debris quantity and distribution.

The above two sampling approaches rely heavily on the fact that significant wear debris

is picked by the lubricant and circulated throughout the lubrication system. A prime factor affecting this debris circulation is the lubricant filter. This filter is designed to remove debris from the lubricant. Traditionally, lubricant filtration has been relatively

coarse thus ineffective in removing significant wear debris from the lubricant. Recently,

however, equipment lubricant filtration has been improving. This improvement is being

driven by the realization of the deleterious accelerating effects of lubricant borne debris,

on the system wear rate. Improved filtration will eventually lead to the condition where significant wear debris will no longer be circulating in the system, it will be for the most

part, entrapped in the filter. This condition will tend to nullify the effectiveness of

both present in-line and off-line sampling approaches. Drastic modifications of present

sampling techniques will have to be developed in order to obtain a representative wear

debris sample from a highly filtered system.

7. Health Monitoring Equipment

A second critical aspect in the wear particle analysis approach, is the analysis equipment. The equipment proposed under previous sections include an in-line particle counter, a laboratory particle counter, a spectrometer, and a ferrograph.

In order to fully implement this proposed equipment approach, several problems have to

be overcome. These problems fall into two categories; equipment development and procedural

development. Equipment development problems involve the in-line particle counter and the spectrometer.

Lack of a demonstrated in-line particle counter with required application durability and sensitivity, creates a major void in the proposed analysis approach. Spectrometer insensitivity to large wear debris particles, although a short-coming, presents itself as less of a severe problem. Both of these problem areas are receiving research emphasis and should be resolved in the near future.

335
Equipment procedural problems involve analysis equipment repeatability. Necessary standardization and calibration procedures have not been developed for the total equipment

package. This situation hinders quantitative wear debris analysis as well as inter- laboratory joint monitoring efforts. Although some standardization efforts are presently

being implemented, the equipment calibration area requires further investigation.

8. Wear Particle Analysis Interpretation

The third and final critical wear particle analysis aspect is analysis interpretation. Assuming a valid sample has been obtained and a pertinent equipment analysis has been performed, one must then proceed to relate generated data to the respective equipment wear con- dition. This process involves considerable interpretation and is complicated by equipment

characteristics, operating parameters, and operating environment. Equipment characteristics will have a decided effect on the four critical monitored

parameters. Such characteristics as number of wearing components, equipment materials,

lubricant, lubricant capacity, and filtration level will all tend to complicate wear debris analysis results. Equipment operating parameters will also effect wear debris parameters thus, wear

debris analysis. Parameters such as load, speed, and operating cycle have to be considered

in the wear particle interpretation process.

The third factor, operating environment, can affect the wear rate of the respective equipment as well as directly contribute to the oil borne debris circulated by the equipment. These effects will further tend to distort/complicate wear debris analysis results.

In order to counter these interpretation challenges, one must rely on a combination of trending techniques, equipment knowledge, and monitoring experience. Trending of monitored

parameters will serve to highlight pertinent parameter changes with respect to a particular

equipment. Parameter trending as opposed to parameter standard comparisons, will tend to minimize the distorting effects of equipment operating parameters and operating environment.

An in-depth technical knowledge of the monitored equipment is very advantageous with

respect to wear particle analysis. This knowledge is especially useful in minimizing the complicating effects of equipment characteristics.

Finally, monitoring experience serves to fine-tune wear particle analysis interpretation. The experience factor tends to minimize all three of the interpretation distortion

elements. This factor is the most critical in any wear particle analysis application.

In order to implement the above discussion and thus complete the wear particle analysis application process, the following approach is proposed. To effectively develop interpreta- tion capability, an in-depth knowledge of the monitored equipment must first be acquired. Once acquired, control groups of respective equipment must be established and monitored on

a trial basis. This trial program will serve to establish wear trends and analysis criteria. Once developed, these trends and criteria can be applied to the total inventory of equipment of the respective type.

9. Wear Particle Analysis Health Monitoring Payoff

The application of wear particle analysis as a health monitoring technique, exhibits numerous potential advantages over present oil analysis techniques (i.e., spectrometric oil analysis). These advantages are composed of both general and specific elements directed at the operation and maintenance of mechanical equipment. General advantages include increased availability, decreased maintenance cost, increased life, and increased safety. Specific advantages are an increased monitoring effectiveness with a decreased sample

workload. It is projected that monitoring effectiveness can be raised from the present

level of 60 percent to an oil wetted component wear abnormality detection efficiency of 90+ percent. By utilization of the detection approach, laboratory sample analysis workload

will be cut down by approximately 75 percent. This decreased sample workload, although somewhat offset by increased individual sample analysis requirements, will tend to decease

the number of required laboratories.

336
A less obvious payoff of wear particle analysis is the potential expanded application

of the technology. Hydraulic and grease lubricated component diagnostics, design assistance, quality assurance, and trouble shooting are a few of the potential expanded areas. These general and specific wear particle analysis payoffs will result in substantial time,

cost, manpower, energy, and material savings for both the governmental and industrial communities.

10. Summary

Recent resource limitations have prompted considerable interest into the area of mechanical equipment wear integrity optimization. A prime consideration under this optimization

effort, is the application of wear particle analysis technology to equipment health monitoring. This technology relates the wear debris parameters of quantity, size distribution, com- position, and morphology to system wear rate, wear severity, wear source, and wear type. Monitoring of these critical wear debris parameters, through a specific decision process, uilizing pertinent analysis equipment, will serve as a viable health monitoring approach.

This wear particle analysis health monitoring approach requires special attention to the critical application areas of sampling, analysis equipment operation, and analysis

interpretation. These areas can easily distort the effectiveness of wear particle analysis. The potential payoff of wear particle analysis health monitoring is substantial. It impacts the areas of manpower, materials, energy, time, and cost savings. These potential

savings are applicable to both the governmental and industrial communities. References

[I] Dalai, H. , et al., Progression of Surface Damage and Oil Wear Debris Accumulation in Rolling Contact Fatigue, U.S. Naval Air Engineering Center, final report on contract

number N00156-74-C-1634, SKF Report A175T007 (1975).

[2] Leonard, L. , et al . , Analysis of Sliding Wear in a Test Diesel Engine, U.S. Naval Air Engineering Center, final report on contract number N00156-73-C-0764.

[3] Wescott, V.C., et al., Oil Analysis Program, U.S. Naval Air Engineering Center, final report on contract number N00156-74-C-1682, Foxboro-Trans Sonics Report (1975).

[4] Bowne, C. R. and Siefert, W. , Ferrography - a new tool for analyzing wear conditions,

Fluid Power Testing Symposium (1976).

[5] Scott, D. and Seifert, W.W. , Ferrography - a new tool for analyzing wear conditions,

Fluid Power Testing Symposium (1976).

[6] Dalai, H. and Senholzi, P.B., Characteristics of wear particles generated during

failure progression of roller bearings, ASLE paper presented at ASLE Annual Meeting

(1976).

[7] Senholzi, P. B. , Tri service R&D oil analysis program - background, description, and results, Fluid Power Research Conference (Oct. 1975).

[8] Senholzi, P.B., Tri service oil analysis R&D program, Mechanical Failures Prevention

Group (1975).

[9] Senholzi, P.B., Technical approach to the exploratory development oil analysis program,

U.S. Naval Air Engineering Center.

[10] Senholzi, P.B. and Bowen, C.R. , Oil analysis research, National Conference on Fluid

Power (Oct. 1976).

[II] Senholzi, P.B., Oil analysis/wear particle analysis, Mechanical Failures Prevention

Group (1977).

337
[12] Senholzi, P.B., Oil analysis/wear particle analysis II, Institute of Mechanical

Engineers, (1978). [13] Maciejewski, A., Oil analysis aspects of tribology, Fluid Power Research Conference,

(1979).

338
National Bureau of Standards Special Publication 584. Proceedings of Joint Conference

on Measurements and Standards for Recycled Oil /Systems Performance and Durability held at NBS, Gaithersburg, MD, October 23-26, 1979. (Issued Nov. 1980)

MECHANICAL FAILURES AND LUBRICATION PERFORMANCE

Marshall B. Peterson Wear Sciences, Inc. 925 Mallard Circle

Arnold, MD 21012

1. Introduction

In order to assure a consistent system performance it is necessary to understand the causes and the processes by which mechanical failures occur. If one tries to understand

mechanical failures he reaches a certain dilemma illustrated by the list of bearing failures

shown in table 1. The difficulty with the list is that it is a mixed bag of mistakes

(design, manufacturing and service related), processes (fatigue, wear, corrosion), causes

(low on oil, improper crush), and results (scoring). This same situation applies to almost

all components. An early task of MFPG was an attempt to collect and organize the technical literature in the area of mechanical failures [l] 1

. Forty thousand abstracts were reviewed. Chapters were prepared which covered failures of various components. If one summarizes the failures listed for each component, a list of "component malfunctions" can be identified as shown in table 2. These "component malfunctions" are the reasons why a component is removed

replaced, or repaired; they are the end results of various failure processes. These failure processes are considered in the following sections. Table 1. Causes of bearing failure.

Oil Passages Plugged

System Low on Oil

Mi sal ignment Shock Loads Poor Surface Finish

Dirt Lubricant Degradation

Lubricant Deterioration

Improper Viscosity

Excessive Temperatures

Poor Materials

Differential Thermal Expansion

Dimensional Instability

Excessive Sliding

Poor Thermal Conductivity

Corrosion

Fatigue Wear

Improper Dimensions

Improper Crush Scoring

Figures in brackets indicate the literature references at the end of this paper.

339
Table 2. Component malfunctions Component

Mai function Seal Brake

Rol 1 ing

Con*tr3ct Bearing Gear

SI i di ng Bearing Inadequate Friction High Friction Fade High Torque Noisy Squeal Vibration/Unstable Instabi 1 ity Whirl

Di storti on/Deform Deformation Plastic Flow Plastic Flow Fracture i Fracture Fracture

Surface Damage

Loss of Lube- Smearing ScoringLoss of Lube- Seizure Worn Wear High Wear

Cage Wear- Bearing Wear Wear

DirtLoss of Lube Fatigued Heat Check Fatigue

PittingSpal 1 i ng Fatigue Corroded Corrosion Corrosion

2. Failure Processes - Lubrication

The failure process is illustrated in figure 1 using tribology (lubrication) as an example. In any component where there is rolling or sliding, a variety of dissipative

processes are going on. These processes can lead to a variety of malfunctions depending upon

the specific component and application in question. These malfunctions will be classified as failures if they interfere with the system requirements. Either they prevent the component

from fulfilling its function or the performance has deteriorated to some preestabl ished

limits. The dissipative processes are universal in that they apply to all components; malfunctions are specific in that they depend upon the circumstances to which they are applied. What may be a failure in one bearing in one application may not be considered a failure in the same bearing in another application.

TRIBOLOGICAL POTENTIAL ! SYSTEM OR

DISSIPATIVE COMPONENT COMPONENT PROCESSES

1 MALFUNCTIONS REQUIREMENT

ADEQUATE BEHAVIOR

HEATING $ HEAT CYCLING

PLASTIC DEFORMATION CRACK FORMATION § PROPAGATION

CUTTING § TEARING ADHESION $ TRANSFER

MATERIAL DIFFUSION OR

REACTION MATERIAL REACTION WITH

ENVTORNMENT

THERMAL EXPANSION/ CONTRACTION

INADEQUATE FRICTION NOISY VIBRATION/UNSTABLE

DISTORTED/ DEFORMED

FRACTURE SURFACE DAMAGE WORN

FATIGUE CORRODED

OPERATION FUNCTIONAL MALFUNCTION REQUIREMENTS

LIMITS TRANSMIT MOTION

DISSIPATE ENERGY

LOCATE SEAL MOTION INTERFACE

Figure 1. Failure processes.

340
In the component the operating conditions will determine wh-ich dissipative process predominates and what the role of the lubricant will be. The better these processes are understood the more they can be taken into account in the component design. This is described in more detail in the following section.

3. Causes of Failure

The various stages in the life of a component are described in figure 2. In the conceptual stage the designer knows the system requirements, and the desired life he is trying to achieve. Based upon his knowledge of the dissipative processes the various components are designed or selected. Basically, this design sets the operating conditions.

Each component is manufactured, assembled, started up, and "run in". These processes lead to

an operating tribological contact which, because of imperfections in the manufacture and assembly and because of changes during "run in", lead to a new set of operating conditions.

In the operating contact the dissipative processes are initiated and will continue until

a malfunction occurs. All of the dissipative processes act simultaneously and it is a race

to see which can destroy the contact first. "Which one wins" is a function of operating

variables and the limits set on the malfunctions. However, some major changes occur with

time. These changes also influence the dissipative process. As far as lubrication is concerned, the system changes of significance are the area, misalignment, and the occurrence

of overloads and excessive temperatures, not anticipated in the design. Even more important

are changes in the lubricant. These changes are usually the cause of failure, not the design.

4. Malfunction Limits

In the design or operation of a component, certain limits are set on the malfunctions.

We will tolerate a certain amount of friction or a certain amount of noise before the component is replaced or repaired. If the malfunctions are not expected they are called

"failures". If they are expected we say the component is "worn out". The condition of the lubricant can lead to all of the malfunctions listed in figure 2. In fact, exactly the same lubricant could lead to all of those malfunctions in the same

component. Different applications are more sensitive to certain malfunctions. However, the most frequent malfunction associated with the lubricant is wear and fatigue. Fatigue has been addressed in a previous paper by Rowe. The affect of the lubricant and changes in the lubricant can be seen in figure 3. Here

the life of a typical bushing is plotted against the wear coefficient where

W = Wear volume = .001 in.

H = Hardness

L = Load

V = Velocity

t = time

K's are collected from the literature for the stated conditions. A typical bushing designed

for fluid film lubrication will give an exceedingly long life (10 000 yr) under the operating

conditions selected. If there is a transition to boundary lubrication that life will be cut

to one year. The addition of improved additives would increase the life to maybe five years.

If the lubricant becomes contaminated with water or becomes acidic, corrosive wear will result

and life will be cut to one day. If the lubricant cannot reach the contact surface, usually

the results of deposits or lack of lubrication, the life would be approximately two hours. If the lubricant becomes severely contaminated with dirt, the life will be a matter of minutes. Our favorite approach to wear problems, changing hardness, has a minor effect on life. Lubrication performance is determined primarily by the condition of the system and the

lubricant. Design efforts should be directed toward those factors affecting the condition of the lubricant.

KLVt

W " H
KNOWLEDGE OH DISSIPATIVE PROCESSES DESIRED LIFE SET OPERATING CONDITION'S LOAD SPEED

CONTACT AREA

TEMPERATURE

CLEARANCE MATERIALS

HARDNESS FINISH

lubricant viscosity

lube quantity film thickness

SIZE SURFACE CONFIGURATION

CONTAMINATION

NEW SET OF OPERATING CONDITIONS

- SYSTEM CHANGES AREA

MISALIGNMENT OVERLOAD OVER TEMPS LUBRICANT CHANGES

OXIDATION

ADDITIVE DEPLETION

CONTAMINATION, WATER, ETC. DIRT, WEAR PARTICLES

DEPLETION VISCOSITY

INADEQUATE FRICTION _ NOISY VIBRATING/UNSTABLE

DISTORTION

FRACTURE

SURFACE DAMAGE CORROSION

WEAR

FATIGUE

Figure 2. Causes of failure.

342
Figure 3. Effect of lubricant condition on life.

343

LIST OF ATTENDEES

345

JOINT CONFERENCE ON MEASUREMENTS AND STANDARDS FOR RECYCLED OIL/SYSTEMS PERFORMANCE AND DURABILITY

National Bureau of Standards Washington, DC 20234 October 23-26, 1979

Final Registration List

C. E. Aldhizer

Federal Trade Commission

6th & Pa. Avenue NW Washington, DC 20580

M. Alphandary

Exxon Co. USA (Research Centre)

Linden Ave. Linden, NJ 07036 Dean Arlidge

Pfaudler

Division of Sybron Rochester, NY 14603

James A. Armstrong

Environment Canada

351 St. Joseph Blvd. Hull , Quebec K1A 1C8 CANADA

Carol M. Ashley

Consumer Standards Div. North Carolina Dept. of Ag.

P. 0. Box 26056

Raleigh, NC 27611

Dan Barber Baumgardner Oil Co. , Inc.

R. R. #1 Box 611 Fayetteville, PA 17222 David B. Barton

Mobil Research & Development Corp. Paulsboro, NJ 08066 Donald A. Becker

National Bureau of Standards Office of Recycled Materials Washington, DC 20234 Siegfried Bellinger

Dentsche BP - Hamburg

Hamburg, GERMANY

Joseph G. Berke

National Bureau of Standards Office of Recycled Materials

Washington, DC 20234

M. K. Bhargava Chemoleums Private Limited Thiruneermal ai Road Chromepet Madras 44 MADRAS

S. Bhattacharyya

IIT Res. Inst. 10 W. 35 Chicago, IL 60616 Mary Jo Bieberich

Code 2832 David Taylor Naval Ship R&D Center

Annapolis, MD 21402 Stephen Bonifazi Pratt & Whitney Aircraft

Box 2691 West Palm Beach, FL 33402 George T. Booth III Booth Oil Co. , Inc. 76 Robinson Street

N. Tonawanda, NY 14120 John N. Bowden Southwest Research Institute

P. 0. Drawer 28510

San Antonio, TX 78284

Thomas Bowen

U.S. Army Mobility Equip. Res. &

Devlp.

Ft. Belvoir, VA 22060

Lyle Bowman Chevron USA

555 Market Street

San Francisco, CA 94105

P. Brassart

President Syndicat Fraucais

des Re-roffuiranic

44 rue Ca Boetie

Paris FRANCE
James Breece

Safety Kleen Corp. 655 Big Timber Rd Elgin, IL 60120 Richard F. Bridges

Oil Savings, Inc. Suite 403 2480 Windy Hill Rd. Marietta, GA 30067

Fred E. Brinckman

National Bureau of Standards Washington, DC 20234

Dennis W. Brinkman DOE/Bartlesville Energy Tech. Ctr. Box 1398 Bartlesville, OK 74003

Lee Brodsky

Exxon Chemical Company

P. 0. Box 536 Linden, NJ 07036 Henrietta Brown

National Bureau of Standards Washington, DC 20234

Alex D. Bull Imperial Oil Limited

111 St. Clair Ave. W. Toronto, Ontario

CANADA

Harry C. Burnett

National Bureau of Standards Materials Bldg. Room B-264 Washington, DC 20234

M. Tylor Burton

Key Petroleum, Inc. Skywater Road Gibson Island, MD 21056

Douglas M. Cameron

Turbo Refineries Ltd. Box 5827 Station L Edmonton, Alberta, CANADA

Norma Cameron

State Dept. of Administration

50 Sherburne Avenue

St. Paul, MN 55155 Andrew Carson Westville Oil & Mfg. Co. Box 587 Westville, IN 46391

Ken Cashmore

Gulf Canada Ltd. 2489 North Sheridan Way

Sheridan Park, Ontario L5K 1A8 CANADA

Tai S. Chao Atlantic Richfield Co. 400 E. Sibley Blvd. Harvey, IL 60426 Stephen Chesler

National Bureau of Standards Washington, DC 20234 Rustam Chinoy

Mechanical Technology, Inc. 968 Albany/Shaker Road

Latham, NY 12110 Barbara Clark

Catepi 1 lar Tractor

100 Northeast Adams St. Peoria, IL 61629 Jack Comeford

National Bureau of Standards Recycled Oil Program Washington, DC 20234 Phillip Cowan

Husky Oil Co.

P. 0. Box 380 Cody, WY 82414

Thomas D. Coyle

National Bureau of Standards Washington, DC 20234 Stanley R. Craft Chromaspec Labs, Inc.

P. 0. Box 71 716 D Montana

South Houston, TX 77587 James A. Creedon

The Lubrizol Corporation

29400 Lakeland Blvd. Wickliffe, OH 44092

R. G. Crumley

National Bureau of Standards Washington, DC 20234 Art Cummings

National Bureau of Standards Recycled Oil Program Washington, DC 20234

348
George I. Davis David Refining Corporation

P. 0. Box 6089 Tallahassee, Fl_ 32301

James Ed Davis Arkansas Dept. of Energy

300 Kavanaugh

Little Rock, AR 72205 Jack M. Deaton Cummins Engine Co. 1900 McKinley Ave. Columbus, IN 47201

Peter R. DeBruyn

National Bureau of Standards

Industrial Liaison Washington, DC 20234

Charlie Donaldson

Federal Trade Commission

6th & Pennsylvania Ave., NW Washington, DC 20580

R. W. Drexler

Lubricants, Inc.

P. 0. Box 46 Pewaukee, WI 53072

Die Driver

Foxboro/Analytical Inc.

P. 0. Box 435 Burlington, MA 01803

Don Eastep Illinois Institute of Natural Resources Springfield, IL 62706

Rolf Eder AMMRA Arbeitsgemeinschaft

Mittel standi scher Mineralol- Raffinerien e.V. 200 Hamburg 1 Gurl ittstrape 31 Donald J. Edwards

Mobil Oil Corp. 150 E. 42nd St. New York, NY 10017 Donald G. Espey

Exxon USA

P. 0. Box 2180

Houston, TX 77001

L. Estaque

Ecole Polytechnique Montreal

P 6079 "A" Montreal, CANADA

Daniel Fairchild

Fram Corp.

55 Pawtucket Avenue

E. Providence, RI 02916 Jim Fay

ALM, Inc. 1745 Jefferson Davis Hwy Arlington, VA 22202 Edward Forgeron Analysts Inc. 655 Deep Valley

Rolling Mills Estate, CA 90274

Kenneth A. Frassa

Mobil Oil Corporation

150 E. 42nd Street

New York, NY 10017 Werner Fries

Fed. Office for Military

Technol . & Procurem.

K. Adenauer UFER 2-6

D54 Koblenz GERMANY

D. R. Gardner

Shell Canada Lab 505 University Ave. Toronto M5G 1X4 CANADA

Richard Gates

National Bureau of Standards Office of Recycled Materials

Washington, DC 20234

A. Gianni Stauffer Chemical Co. Nyala Farm Road Westport, CT 06880

C. F. Goeking, Jr. Shell Development Company

P. 0. Box 1380 Houston, TX 77001

H. S. Golinkin

Amoco Chemicals Corporation

P. 0. Box 400 Naperville, IL 60540 Elizabeth Gorecki Edwards Oil Service, Inc. 530 Rouge Detroit, MI 48217

Richard Gorecki Edwards Oil Service, Inc. 530 Rouge Detroit, MI 48217

349
C. C. Gravatt

National Bureau of Standards

National Measurement Lab. Washington, DC 20234

L. H. Handler

Suntech, Inc.

P. 0. Box 1135 Marcus Hook, PA 19061 Wildrick Hart Witco Chemical Corp.

77 N. Kendall Ave. Bradford, PA 16701 Rudolf Havemann

Haberland & Co. Mineralol-Raffinerie

Bahnofstr. 82 Dollbergen, 3161 WEST GERMANY

J. H. 0. Hazewinkel Kinetics Tech. International

26 Vredewater

2700 A. B. Zoetermeer

THE NETHERLANDS

Leslie R. Heerdt

Favi 1 le-LeVal ley Corp. 2753 Curtiss Street Downers Grove, IL 60515 Henry R. Hegner ManTech of New Jersey Corp. 2341 Jefferson Davis Highway

Arlington, VA 22202 Walter W. Hellmuth

Texaco Inc.

P. 0. Box 509 Beacon, NY 12508 Jacque D. Heyen Petroleum Recycling Corp.

P. 0. Box 10713 Knoxville, TN 37919 Robert R. Holden

Hughes Aircraft Co. Bldg. 117 Mail Sta. 1

P. 0. Box 90515

Los Angeles, CA 90009

Paul Howard

E&MR Co. 964 Sweresford Road

Exton, PA 19341

Stephen Hsu National Bureau of Standards Office of Recycled Materials Washington, DC 20234 Conrod B. Johnson Turbo Refineries

94 Ave. & 34 St. Edmonton, Alberta, CANADA

Donald R. Johnson

National Bureau of Standards

National Measurement Laboratory Washington, DC 20234 Walter B. Johnson

Technical Center

Deere & Co. 3300 River Drive Moline, IL 61265

G. Kelkar

Caltex Petroleum Corp. 380 Madison Ave. New York, NY 10017 Warren C. Kelliher

Viking Project Office

NASA

Hampton, VA 23665

Vicki L. Ketvirtis

Div. of Oil, Gas, & Minining

State of Utah

1588 W. No. Temple

Salt Lake City, UT 84116 Robert L. Kincaid Spectron Car i be, Inc. Cond. Las Lomas #1 Caparra Heights, PR

E. E. Klaus Pennsylvania State University

133 Chemical Eng. Bldg. University Park, PA 16802

Michael Klinkhammer

D. T. Naval Ship R&D Ctr. Code 2832 Annapolis, MD 21402

R. L. Klug Caterpillar Tractor Co. Serv. Development

Pioneer Park

East Peoria. IL 61630

350
Hans O.A. Koehn Mineralol-Raffinerie Weiss Co. Schmidts Breite 3 Hamburg 93, 2102 WEST GERMANY

M. Kolobielski

US Army Meradcom

6710 Sherwood Rd. Baltimore, MD 21239 Stefan Korcek

Ford Motor Company

P. 0. Box 2053 Dearborn, MI 48121

Richard L. Kornmann Amoco Chemicals Corp. 200 E. Randolph Drive

Chicago, IL 60601

Tom Kosh Edwards Oil Service, Inc. 530 Rouge

Detroit, MI 48217

A. J. Koury

Naval Air Systems Command AIR-4114C

Washington, DC 20360 Sharon H. Kneiss Gulf Research & Dev. Co.

P. 0. Drawer 2038 Pittsburgh, PA 15230 Chia-Soon Ku National Bureau of Standards Washington, DC 20234 Christian LaFrenz

Fa. Haberland & Co. Mi neralol-Raff inerie

Bahnhofst. 82 Dollbergen, 3161 WEST GERMANY

Richard Lee US Army/JOAP-TSC

5950 Keystone Rd. Pensacola, FL 32504

Leonard H. Lemon Energy & Minerals Research Co. 964 E. Swedesford Road

P. 0. Box 389 Exton, PA 19341

Robert Lindquist

111. Institute of Natural Resources

325 W. Adams - Rm 300 Springfield, IL 62558

R. E. Linnard Phillips Petroleum Co. 429 TRW Building

Bartlesville, OK 74004 Donald A. Littlefield

ATC Petroleum, Inc. Old Dover Road Newington, NH 03801

Eugene S. Lubarsky

A. Johnson & Co. 110 E. 59th Street

New York, NY 10022 John A. Ludquist Quaker State Oil Refining Corp. Research Center

P. 0. Box 989

Oil City, PA 16301

James A. McBain Association of Petroleum

Re-refiners - Suite 700 1101 Connecticut Avenue, NW Washington, DC 20036 James F. McCadden

Baird Corp. 125 Middlesex Turnpike

Bedford, MA 01730 Edward W. McCrary

Louisiana Oil & Re-refining

2156 Scenic Highway

Baton Rouge, LA 70802 Alan Mac ie jews ki Naval Air Engineering Ctr. Code 92724

Lakehurst, NJ 08733

H. P. Martin

Office of Naval Research

Code 211 Arlington, VA 22217

Peter M. Mehiel EkoTek Lube, Inc. 7901 Oakport St. , 140 So. Oakland, CA 94621

David Mentzer

Exxon Research & Engineering Co.

P. 0. Box 101 Florham Park, NJ 07932

351
Louis A. Mileto

Systems Engineering Test

Di rectorate

Naval Air Test Center Patuxent River, MD 20670 Thomas Myers

Booz, Allen & Hamilton

4330 East West Highway

Bethesda, MD 20014 Christian D. Nelson

Armco

4805 Longford Dr. Middletown, OH 45042

Ray Nye Wills Oil Co. Ltd. 533 Powell Street Vancouver, BC V6A-1GA

CANADA

John P. 0'Connell Estech Oil Company

7601 West 47th Street

McCook, IL 60525

David H. Parent

3400 Custer Road, Apt. 2040

Piano, TX 75023

E. Passaglia

National Bureau of Standards Materials Bldg. Room B-308 Washington, DC 20234

Robert F. Pedal 1 Motor Oils Refg. Co. Estech Oil Co. 7601 W 47th St. McCook, IL 60525 Patrick Pei National Bureau of Standards Office of Recycled Materials

Washington, DC 20234

Glen A. Peters AT&SF Railway Company

P. 0. Box 536 Barstow, CA 92311

I. C. Peterson Hydromatic Division

General Motors

Ypsilanti, MI 48197

Marshall Peterson Wear Sciences

925 Mallard Circle

Arnold, MD 21012

D. G. Phillips

Md. Environmental Service

60 West St. Annapolis, MD 21401 Jack Poley Lubricon

30 Horseneck

Montville, NJ 07045

John S. Poupore Consulting Engineer Contact Work on Oil Refining Government of Canada

Ottawa, CANADA KIN 8MI

R. Rebbert

National Bureau of Standards Washington, DC 20234

Richard L. Riedel The Standard Oil Co. 3092 Broadway

Cleveland, OH 44115

A. L. Rollin

Ecole Polytechnique

Chem. Eng. Dept. CP 6079 Montreal, CANADA Carleton Rowe

Mobil Research and Development

Box 1025 Princeton, NJ 08540

J. Rowland

BP Trading, Ltd. Britannic House, Moor Lane

London, ENGLAND EC2Y 9BU

A. W. Ruff National Bureau of Standards Materials Bldg., Room B-114 Washington, DC 20234

C. Salvesen

Mobil Research & Development

Box 1025 Princeton, NJ 08540 Eugene W. Sanders

Cities Service Company

P. 0. Drawer #2 Cranbury, NJ 08512

Lowrie B. Sargent, Jr. Aluminum Co. of America Alcoa Laboratories Alcoa Technical Center

Alcoa Center, PA 15069

352
John W. Schulte

The Lubrizol Corp. Wickliffe, OH 44092

Charles Schwarz

Martel Laboratories

1025 Cromwell Bridge Rd. Baltimore, MD 21204

Adam Scott

North Carolina Dept. of Ag. Consumer Standards Div.

P. 0. Box 26056

Raleigh, NC 27611 Morton Segal Petrocon Corporation

Union Street

P. 0. Box 96 Modena, PA 19358 Theodore W. Selby

Savant, Inc. 234 E. Larkin

Midland, MI 48640

Peter Senholzi Mechanical Technology Inc. 1745 Jefferson Davis Highway

Crystal Square 4, Suite 301 Arlington, VA 22202

E. J. Shalling

The Torrington Co. 59 Field Street

Torrington, CT 06790

W. A. Shelton

Union Carbide Corp. Tech. Ctr.

P. 0. Box 8361

South Charleston, WV 25303

T. R. Shives

National Bureau of Standards Materials Bldg., Room A- 111 Washington, DC 20234 John B. Skiba

Pennzoil Company

P. 0. Box 8989

Richmond, VA 23225 Richard Slocum Ministry of Transportation & Communications

1201 Wilson

Downsview, Onatrio

CANADA

R. A. Smucker

Gulf Research & Dev. Co.

P. 0. Drawer 2038 Pittsburgh, PA 15230

Ernest F. Spano

US Army Aviation Ctr. & Ft. Rucker

ATTN: ATZQ-DI-S/S (Oil Analysis Sec)

Ft. Rucker, AL 36362

Ilgvars J. Spilners Gulf Science & Tech.

P. 0. Drawer 2038 Pittsburgh, PA 15230

Leon Stal lings

Naval Air Develop. Center

Code 60612 Warmiasler, PA 18042

Wi 11 iam C. Starr

Mobil Research & Dev. Corp. Research Dept. Paulsboro, NJ 08066 David M. Stehouwer

Fuels and Lubricants Dept. General Motors Res. Labs. Warren, MI 48090

J. E. Stern NASA/Goddard

Code 721 Greenbelt, MD 20771

Roy J. Street MoHawk Lubricants Ltd. 6400 Roberts Street

Burnaby, BC V5G 4G2

Paul Strigner

National Research Council

of Canada

Div. of Mechanical Eng. Ottawa, CANADA K1A 0R6 John W. Swain, Jr. Swain Associates

40 Denton Road Welles leg, MA 02181

E. S. Swanson, Jr. Exxon Corporation

P. 0. Box 389 Florham Park, NJ 07932

H. Ed Taber Taber Oil Co. 835 Madison St. Port Clinton, OH 43452

353
Thomas A. Tagliamonte

The Lubrizol Corporation

29400 Lakeland Blvd. Wickliffe, OH 44092

Jerry L. Thompson

Amoco Oil

P. 0. Box 400 Naperville, IL 60540 Harold E. Tiffany

American Petroleum Institute

2101 L Street Washington, DC 20037

W. Tsang

National Bureau of Standards Washington, D. C. 20234

Mike Valtierra

Army Fuels & Lubricants Res. Lab.

P. 0. Box 28510

6220 Culebra Road

San Antonio, TX 78284

John T. Vrombaut

Technical Center

Deere & Co. 3300 River Drive

Moline, IL 61265 James Walker

National Bureau of Standards Washington, DC 20234

John G. Walsh

Husky Oil Co. 600 S. Cherry St. Denver, CO 80222

Michael S. Ward

Tennessee Oil & Refining, Inc. Highway 109 Portland, TN 37148 Stephen Weeks

National Bureau of Standards Office of Recycled Materials

Washington, DC 20234

Ken Weinstein

Booz, Allen & Hamilton

4330 East West Highway

Bethesda, MD 20014 Norman J. Weinstein

Recon Systems, Inc.

P. 0. Box 842

Some rvi lie, NJ 08876

Jerry Wilkins

Suntech Inc. 1608 Walnut Street

Philadelphia, PA 19103

W. A. Willard

National Bureau of Standards Materials Bldg. Room B-128 Washington, DC 20234

T. A. Wilson

Dal ton & Company Limited Silkolene Oil Refinery

Bel per, Derbyshire DE5 1WF ENGLAND

Keith L. Winegar

Intermountain Oil Co. Woods Cross, UT 84087

Harvey Yakowitz

National Bureau of Standards Recycled Oil Program Washington, DC 20234

354
NBS-114A rev. 2-8C BIBLIOGRAPHIC DATA

SHEET (See instructions)

1. PUBLICATION OR REPORT NO. NBS SP 584

2. Performing Organ. Report No 3. Publication Date November 1980

• TITLE AND SUBTITLE Joint Conference on Measurements and Standards for Recycled Oil/Systems Performance

and Durability held at the National Bureau of Standards on October 23-26, 1979.

5.#HXWC«{X)X Edited by Donald A. Becker

6. PERFORMING ORGANIZATION (If joint or other than NBS, see instructions) NATIONAL BUREAU OF STANDARDS DEPARTMENT OF COMMERCE

WASHINGTON, D.C. 20234

7. Contract/Grant No.

8. Type of Report & Period Covered Final

9. SPONSORING ORGANIZATION NAME AND COMPLETE ADDRESS (Street. City, State, ZIP) Recycled Oil Program, NBS; ASTM Technical Division P, on Recycled Petroleum Products;

Mechanical Failure Prevention Group (MFPG); Center for Materials Science, NBS; Office

of Naval Research; Department of Energy; NASA/Goddard Space Flight Center; Naval Air

Systems Command.

10. SUPPLEMENTARY NOTES Library of Congress Catalog Card Number: 80-600159

I ' Document describes a computer program; SF-185, FlPS Software Summary, is attached.

,11. ABSTRACT (A 200-word or less factual summary of most significant information. If document includes a significant ~

bibliography or literature survey, mention it here) This publication is a formal report of the Joint Conference on Measurements and Standards for Recycled Oil/Systems Performance and Durability held at the National

Bureau of Standards on October 23 through 26, 1979. There were seven sessions on specific areas, with a total of 32 technical presentations. The subject areas were

as follows: (I) Recent Developments in Recycled Oil, (II) Engine Oil Evaluation,

(III) Lube Oil Base Stock Characterization, (IV) Oil Analysis for Engine Condition

Monitoring, (V) Bench Tests for Oil Evaluation - I, (VI) Bench Tests for Oil Evaluation - II, and (VII) Systems Performance and Durability. Included in this report are

the entire texts of the various presentations, including figures and tables.

|12. KEY WORDS (Six to twelve entries; alphabetical order; capitalize only proper names; and separate key words by semicolons) Engine oil; hydraulic oil; industrial oil; lubricating oil; oil specifications;

petroleum standards; petroleum test methods; recycled oil; re-refined oil; used oil; waste oil

113. AVAILABILITY

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