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 That document has been superseded by the Facility Pollution Prevention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

Colorado State University performed an assessment at a plant

that manufactures pliers and wrenches. The products are manufactured from metal blanks that have been forged in another

plant. In the case of the pliers, the blanks are machined,

etched, primed, and assembled. The handles are then plastic

coated and the finished pliers are inspected, packaged, and

shipped. For wrench manufacture, the metal blanks are nickeland chromium-plated, inspected, and packaged. The team’s

report, detailing findings and recommendations, indicated that

the greatest quantity of waste in this plant came from the

machining and plating operations. The greatest cost-saving

opportunity recommended to the plant involved the replacement of 1,1,1-trichloroethane vapor degreasing with nonhazardous aqueous cleaning.

This Research Brief was developed by the principal investigators and EPA’s Risk Reduction Engineering 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, Philadelphia, PA.

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 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 Risk Reduction Engineering Laboratory, the Science Center has established three WMACs. This assessment was done by engineering

faculty and students at Colorado State University’s (Fort Collins)

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 waste minimization 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 waste minimization.

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.

Waste Minimization Assessment for a Manufacturer

of Pliers and Wrenches

United States

Environmental Protection

Agency

Risk Reduction

Engineering Laboratory

Cincinnati, OH 45268

ENVIRONMENTAL

RESEARCH BRIEF

Research and Development EPA/600/S-94/004 September 1994

Harry W. Edwards*, Michael F. Kostrzewa*,

and Gwen P. Looby**

E AP

* Colorado State University, Department of Mechanical Engineering,

Fort Collins, CO

** University City Science Center, Philadelphia, PA
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Methodology of Assessments

The waste minimization 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

The plant manufactures pliers (adjustable and needle-nose)

and wrenches that are distributed nationally. It operates 7,200

hr/yr to produce almost ten million pieces annually.

Manufacturing Process

The principal raw materials used by this plant are metal blanks

that have been forged in another plant.

Plier Manufacture

In the production of adjustable pliers, the metal blanks are

trimmed and coined to dimension and straightened. Then, one

or two holes are pierced in each blank for the joint connection.

Next, arcs are cut into the blanks using broaches that also cut

teeth into the blanks. The plier handles are then ground using

vertical broaches. Heat treating, sandblasting, and polishing of

the blanks follow.

Brand names are etched on the single-hole blanks using acid.

Then, those blanks are dipped in clear-coat primer that acts as

a sealant and provides corrosion protection. Primer is also

applied to double-hole blanks, but in this case, spray application is used.

The finished halves are assembled using nuts, bolts, and

washers. Plier handles are then dipped in molten plastic for

coating. The finished pliers are allowed to cool, inspected,

packaged, and shipped.

The processes used in needle-nose plier manufacture are

similar to those used in producing adjustable pliers. In this

case, however, the pliers are etched using a laser instead of

acid. In addition, vapor degreasing is required before plastic

coating.

An abbreviated process flow diagram for plier manufacture is

shown in Figure 1.

Wrench Manufacture

In the manufacture of wrenches, polished metal blanks are

loaded into racks for processing. The racks are sent through

an automated plating machine for electroless nickel-plating and

electrolytic trivalent-chromium-plating. The plated wrenches are

then unloaded, inspected, and packaged.

An abbreviated process flow diagram for wrench manufacturer

is shown in Figure 2.

Existing Waste Management Practices

This plant already has implemented the following techniques to

manage and minimize its wastes:

• Many of the machining operations require no cutting fluid and

therefore generate no waste cutting fluid.

• A cutting fluid reuse program has been developed and

implemented successfully.

• Waste oil is separated from waste cutting fluid and reblended

off-site for use as industrial boiler fuel.

• 1,1,1-trichloroethane has replaced perchloroethylene as the

degreasing agent, thereby reducing slightly the toxicity of the

solvent used for cleaning the pliers.

• The plant plans to replace the spray priming system with a dip

priming system that will generate less waste.

• An acid purification unit (APU) has been installed in conjunction with the nitric acid rack stripper in the plating area. The

APU removes dissolved nickel from the acid so that the bath

can be regenerated without being dumped.

• Nickel plating solution is filtered and reused. Drag-out tanks

are used in the plating line to reduce nickel drag-out into the

rinse streams.

• Liquid nitrogen instead of solvent is used to remove plastic

coating from rejected pliers.

• Whenever possible, waste plastic coating, instead of being

disposed of, is returned to the manufacturer. Cross-contamination of coatings is minimized.

• Flow reducers have been installed on the rinses in the plating

line.

Waste Minimization 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 annual waste management costs are given

in Table 1.

Table 2 shows the opportunities for waste minimization that the

WMAC team recommended for the plant. The minimization

opportunity, the type of waste, the possible waste reduction

and associated savings, and the implementation cost along

with the 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 financial savings of the minimization

opportunities result from the need for less raw material and

from reduced present and future costs associated with waste

management. 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 the savings achievable when implementing each waste

minimization opportunity independently and do not reflect duplication of savings that would result when the opportunities

are implemented in a package.
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Blanks

Piercing

Arc cutting

Teeth cutting

Polishing

Priming

Assembly

Plastic coating

Inspection,

packaging,

shipping Waste

incinerated

off-site

Waste

incinerated

off-site

Solvent

evaporation

Spent solvent

recycled on-site

Solvent

evaporation

Waste cutting fluid

recycled on-site

Acid

etching

Solid-joint and

adjustable pliers

Figure 1. Abbreviated process flow diagram for plier manufacture.

Laser

etching

Vapor

degreasing
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Blanks

Loading

Plating

• Cleaning

• Electroless nickel plating

• Electrolytic chromium plating

Unloading

Inspection

Packaging

Wrenches

Rack stripping

Rejected parts

stripping

Waste incinerated

off-site

Waste to acid

purification unit

Nickel-bearing rinses and

chromium-bearing rinses

to WWTP

Waste alkaline and acidic

solutions to batch treatment

Additional Recommendations

In addition to the opportunities recommended and analyzed by

the WMAC team, two additional measures were considered.

These measures were not completely analyzed because of

insufficient data, minimal savings, implementation difficulty, or

a projected lengthy payback. Since one or more of these

approaches to waste reduction may, however, increase in

attractiveness with changing conditions in the plant, they were

brought to the plant’s attention for future consideration.

• Remove chromium and nickel from rejected parts using an

electro-soap cleaner instead of the currently used stripper.

• Electrowin nickel from the effluent of the acid purification unit

to reduce the amount of nickel discharged to the on-site

waste water treatment system that eventually ends up as

metal hydroxide sludge.

This research brief summarizes a part of the work done under

Cooperative Agreement No. CR-814903 by the University City

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

Lou George.

Figure 2. Abbreviated process flow diagram for wrench manufacture.
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Table 1. Summary of Current Waste Generation

Annual Quantity Annual Waste

Waste Generated Source of Waste Waste Management Method Generated (lb) Management Cost*

Spent cutting fluid Machining (cutting fluid that Shipped off-site to be

 can no longer be reused) reblended into fuel 1,053,410 $88,540

Waste oil Machining (removed from Shipped off-site to be

 cutting fluid during on-site reblended into fuel 103,970 5,630

 recycling)

Reusable cutting fluid Machining (cutting fluid Reused in process 2,041,690 2,100

 that can be reused)

Spent 1,1,1-trichloroethane Vapor degreasing Shipped off-site for incineration 520 900

Still bottoms On-site recycling unit Shipped off-site for incineration 520 900

 for 1,1,1-trichloroethane

Evaporated Vapor degreasing Evaporates to plant air 44,360 21,370

 1,1,1-trichloroethane

Spent perchloroethylene Vapor degreasing Shipped off-site for incineration 13,000 3,440

 (no longer in use)

Waste methyl ethyl ketone Dip priming Shipped off-site for incineration 3,730 6,460

Evaporated methyl ethyl Dip priming Evaporates to plant air 700 450

 ketone

Evaporated xylene Spray priming Evaporates to plant air 10,080 2,600

Waste primer Priming Shipped off-site for incineration 4,100 9,250

Paint filters and rags Spray priming Shipped off-site for incineration 59,480 60,170

Waste plastic coating Plastic coating Shipped off-site for incineration 7,500 14,700

Spent plastic stripper Removal of plastic coating Shipped off-site for incineration 420 260

Spent rinse water Plating line Treated on-site; sewered 22,178,950 54,280

Metal hydroxide sludge Water treatment Shipped to disposal facility 164,330 32,450

Waste metal stripper Removal of plating from pH adjusted; shipped off-site 75,230 31,540

 rejected parts for incineration

Waste solvent Plating line Shipped off-site for incineration 2,250 3,830

Waste buffing compound Machining Shipped off-site for incorporation 3,330 1,530

 into cement

Miscellaneous waste Various processes Shipped off-site for incineration 5,550 3,280

* Includes waste treatment, disposal, handling costs, and applicable raw material costs.
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Table 2. Summary of Recommended Waste Minimization Opportunities

Annual Waste Reduction

Net Annual Implementation Simple

Minimization Opportunity Waste Stream Reduced Quantity (lb) Per cent Savings Cost Payback (yr)

Replace 1,1,1-trichloroethane Spent 1,1,1-trichloroethane 520 100 $21,280 $60,490 2.8

 vapor degreasing with an Still bottoms 520 100

 aqueous cleaning system. Evaporated

 Nonhazardous liquid waste 1,1,1-trichloroethane 44,360 100

 will be generated during

 periodic replacement of the

 cleaner and associated

 rinses if this opportunity is

 implemented.1

Replace the cutting fluid Spent cutting fluid 227,000 22 5,680 11,000 1.9

 currently used in the Reusable cutting fluid 40,000 22

 broaches with a vegetable-

 oil based spray coolant system.

 When used properly, the pro-

 posed oil is consumed com-

 pletely during cutting.

1 It was estimated that a total of 77,000 lb/yr of waste nonhazardous cleaning solution and rinse water will be

generated if this opportunity is implemented.
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BULK RATE

POSTAGE & FEES PAID

EPA

PERMIT No. G-35

United States

Environmental Protection Agency

Center for Environmental Research Information

Cincinnati, OH 45268

Official Business

Penalty for Private Use

$300

EPA/600/S-94/004