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Abstract

The U.S. Environmental Protection Agency (EPA) has funded

a pilot project to assist small and medium-size manufacturers

who want to minimize their generation of waste but who lack

the expertise to do so. In an effort to assist these manufacturers Waste Minimization Assessment Centers (WMACs) were

established at selected universities and procedures were

adapted from the EPA Waste Minimization Opportunity Assessment Manual (EPA/625/7-88/003, July 1988). That document has been superseded by the Facility Pollution Prevention

Guide (EPA/600/R-92/088, May 1992). The WMAC team at

the University of Tennessee performed an assessment at a

plant that manufactures gear cases for outboard motors. Aluminum castings are machined and polished, and undergo chemical immersion, chromate conversion, and, in some cases,

painting. Steel castings are machined, heat treated, shotpeened offsite, deburred, and ground. The finished component

parts are assembled together. The team’s report, detailing

findings and recommendations, indicated that absorbent socks

and leaked oil and coolant are generated in large quantities,

and that significant cost savings could be achieved by eliminating the use of the absorbent socks by constructing containment

areas around the machines.

This Research Brief was developed by the principal investigators and EPA’s National Risk Management Research Laboratory, Cincinnati, OH, to announce key findings of an ongoing

research project that is fully documented in a separate report

of the same title available from University City Science Center.

Introduction

The amount of waste generated by industrial plants has become an increasingly costly problem for manufacturers and an

additional stress on the environment. One solution to the

problem of waste generation is to reduce or eliminate the

waste at its source.

University City Science Center (Philadelphia, PA) has begun a

pilot project to assist small and medium-size manufacturers

who want to minimize their generation of waste but who lack

the in-house expertise to do so. Under agreement with EPA’s

National Risk Management Research Laboratory, the Science

Center has established three WMACs. This assessment was

done by engineering faculty and students at the University of

Tennessee’s (Knoxville) WMAC. The assessment teams have

considerable direct experience with process operations in manufacturing plants and also have the knowledge and skills needed

to minimize waste generation.

The pollution prevention opportunity assessments are done for

small and medium-size manufacturers at no out-of-pocket cost

to the client. To qualify for the assessment, each client must

fall within Standard Industrial Classification Code 20-39, have

gross annual sales not exceeding $75 million, employ no more

than 500 persons, and lack in-house expertise in pollution

prevention.

The potential benefits of the pilot project include minimization

of the amount of waste generated by manufacturers, and

reduction of waste treatment and disposal costs for participating plants. In addition, the project provides valuable experience for graduate and undergraduate students who participate

in the program, and a cleaner environment without more regulations and higher costs for manufacturers.

Pollution Prevention Assessment for a Manufacturer

of Gear Cases for Outboard Motors

ENVIRONMENTAL

RESEARCH BRIEF

Richard J. Jendrucko*, Julia Ann Myers*,

and Gwen P. Looby**

* University of Tennessee, Department of Engineering Science and Mechanics

** University City Science Center, Philadelphia, PA

United States

Environmental Protection

Agency

National Risk Management

Research Laboratory

Cincinnati, OH 45268

Research and Development EPA/600/S-95/028 September 1995
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Methodology of Assessments

The pollution prevention opportunity assessments require several site visits to each client served. In general, the WMACs

follow the procedures outlined in the EPA Waste Minimization

Opportunity Assessment Manual (EPA/625/7-88/003, July 1988).

The WMAC staff locate the sources of waste in the plant and

identify the current disposal or treatment methods and their

associated costs. They then identify and analyze a variety of

ways to reduce or eliminate the waste. Specific measures to

achieve that goal are recommended and the essential supporting technological and economic information is developed. Finally, a confidential report that details the WMAC’s findings

and recommendations (including cost savings, implementation

costs, and payback times) is prepared for each client.

Plant Background

This plant manufactures steel and aluminum lower gear cases

for outboard motors and assorted small steel parts. The plant

operates approximately 6,600 hr/yr to produce almost 200,000

units annually.

Manufacturing Process

Aluminum Part Production

Aluminum castings for gear cases are received and machined

in a series of operations in which they are milled, bored, and

cut. Machined castings which have a light residual surface

coating of coolant following machining operations are allowed

to dry on racks before they are polished.

Approximately half of the machined aluminum castings are

transported to a traditional polishing operation in which the

parts are held against a rotating polishing wheel. The remaining machined aluminum castings undergo a drag-through polishing process in which the parts are fastened to a circular

turntable and pulled through a tank containing a soap and

water solution and abrasives.

All of the polished castings then undergo a series of chemical

immersions to wash the cases and to seal micro-cracks and

pores. A chrome conversion process is utilized to provide

surface corrosion protection and to improve paint adhesion and

surface texture. After the chromate conversion process, the

castings are dried and approximately 99% of them are transported to the lower-unit assembly area. The remaining 1% of

the castings are first painted using hand-held spray guns.

Steel Part Production

Steel gear casting families are received by the plant and

machined in a work cell process configuration. The machined

gears are then transported to the heat treatment area where

they are heated in a large high-temperature oven for hardening. After heat treatment, the gears are quenched in an oil

tank.

The cooled heat-treated gears are shipped offsite to a “shotpeening” process in which the gears are pelted with tiny steel

balls ion order to harden the metal surface, clean rough edges,

and shine dark areas that result from heat treatment.

Gears that have been shot-peened undergo a deburring process in which vibratory slurry stones remove any residual

rough edges. The final inner and outer diameter tolerances of

the gear shaft and shaft hole are achieved in a final grinding

step.

The finished gears are then matched to a fitting pinion and are

dipped in a tank where they receive a coating of oil in order to

prevent rust formation before their use. Approximately 80% of

the gears are transported to the assembly area, and the remaining gears are packaged and shipped to dealers to be sold

as replacement parts.

Assembly

The finished component parts are mounted on racks and transported to one of several different assembly lines dedicated to

different product families. During assembly, seams are sealed

and parts are bolted together. Crankcases are tested and the

accepted units are packaged and shipped to customers.

An abbreviated process flow diagram for the production of gear

cases for outboard motors is shown in Figure 1.

Existing Waste Management Practices

This plant already has implemented the following techniques to

manage and minimize its wastes.

• Alkaline soap is used instead of 1, 1, 1-trichloroethane in the

drag-through polishing process.

• The use of FreonTM for parts cleaning has been eliminated

throughout the plant.

Pollution Prevention Opportunities

The type of waste currently generated by the plant, the source

of the waste, the waste management method, the quantity of

the waste, and the waste management cost for each waste

stream identified are given in Table 1.

Table 2 shows the opportunities for pollution prevention that

the WMAC team recommended for the plant. The opportunity,

the type of waste, the possible waste reduction and associated

savings, and the implementation cost along with the simple

payback time are given in the table. The quantities of waste

currently generated by the plant and possible waste reduction

depend on the production level of the plant. All values should

be considered in that context.

It should be noted that the economic savings of the opportunities, in most cases, results from the reduction in raw material

and costs associated with waste treatment and disposal. Other

savings not quantifiable by this study include a wide variety of

possible future costs related to changing emissions standards,

liability, and employee health. It also should be noted that the

savings given for each opportunity reflect that pollution prevention opportunity alone and do not reflect duplication of savings

that may result when the opportunities are implemented in a

package.

This research brief summarizes a part of the work done under

Cooperative Agreement No. CR-819557 by the University City

Science Center under the sponsorship of the U. S. Environmental Protection Agency. The EPA Project Officer was Emma

Lou George.
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Aluminum

Gear Case

Castings

Machining Drying

Traditional

Polishing

Drag

Through

Polishing

Chemical

Immersions

Chrome

Conversion Drying

Painting

Deburring Grinding

Offsite

Shot

Peening

Quenching Heat

Treating Machining

Steel

Gear

Castings

Parts

Matching

Inspecting

and

Oiling

Replacement

Parts Packaged

and Shipped

Offsite

Finished Product

Shipped to Sister

Plant for use in

Motor Units

Leak

Testing Assembly

Hardware,

Parts

Figure 1. Abbreviated process flow diagram for gear case manufacture.

Table 1. Summary of Current Waste Generation

Annual Quantity Annual Waste

Waste Stream Generated Source of Waste Waste Management Method Generated (lb/yr) Management Cost ($/yr)

Cardboard Parts receiving Shipped offsite to municipal landfill 95,180 $360

Soiled gloves Various plant operations Shipped offsite to municipal landfill 4,160 20

Hydraulic oil and coolant Leaks from machines Shipped offsite to reclaimer 188,000 12,230

Absorbent socks/oil Absorbing of leaked oil and Shipped offsite as hazardous waste 17,640 14,370

coolant from machines

Aluminum dust sludge Polishing Shipped offsite to municipal landfill 913,680 3,410

Spent abrasive Drag-through polishing Shipped offsite to municipal landfill 28,000 100

Filter cake Drag-through polishing Shipped offsite to municipal landfill 1,152,000 4,300

Sludge filter cake Wastewater treatment Shipped offsite as hazardous waste 13,200 7,480

Methyl ethyl ketone/paint Paint line cleaning Shipped offsite to fuels blending program 740 2,410

Steel scrap Machining Shipped offsite 63,900 7,410

Vaporized liquid nitrogen Heat treating Vented 4,982,200 0

Methanol Heat treating Vented 126,590 0

Slurry stones Deburring Shipped offsite to municipal landfill 8,900 30

Filtered particulate metal Grinding Shipped offsite to municipal landfill 76,800 290

Wastewater Various plant operations Treated onsite; sewered 34,997,000 28,580

Dragthrough

polishing
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BULK RATE

POSTAGE & FEES PAID

EPA

PERMIT No. G-35

United States

Environmental Protection Agency

National Risk Management Research Laboratory (G-72)

Cincinnati, OH 45268

Official Business

Penalty for Private Use

$300

EPA/600/S-95/028

Table 2. Summary of Recommended Pollution Prevention Opportunities

Annual Waste Reduction

Quantity Net Annual Implementation Simple

Pollution Prevention Opportunity Waste Stream Reduced (lb/yr) Per Cent Savings Cost Payback (yr)

Construct a containment area around the Absorbent socks 15,880 90 $ 13,150 $ 8,450 0.6

bases of the metal working machines to (See note below)

collect waste oil and coolant instead of

using absorbent socks to do so. Use the

available wet-vacuum to collect the waste

oil and coolant and dispose of it with other

oil waste.

Install a sludge drying oven to reduce the Sludge filter cake 0 —- 5,820 12,000 2.1

mass and volume of wastewater treatment

sludge to be shipped offsite. Although this

opportunity will not lead to waste reduction,

it will lead to lower disposal costs.

Bale the waste cardboard currently shipped Cardboard 0 —- 4,850 10,580 2.2

to the municipal landfill and sell it to a recycling company. Although this opportunity

will not lead to waste reduction, it will lead

to lower disposal costs and revenue for the

plant.

Note: Approximately 12,000 lb/yr of waste oil/coolant will be collected and disposed of (at a much lower unit cost).