&EPA
United States
Environmental Protection
Agency
National Risk Management
Research Laboratory
Cincinnati, OH 45268
Research and Development
EPA/600/S-95/028 September 1995
ENVIRONMENTAL
RESEARCH BRIEF
Pollution Prevention Assessment for a Manufacturer
of Gear Cases for Outboard Motors
Richard J. Jendrucko*, Julia Ann Myers*,
and Gwen P. Looby**
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 manufactur-
ers Waste Minimization Assessment Centers (WMACs) were
established at selected universities and procedures were
adapted from the EPA Waste Minimization Opportunity As-
sessment Manual (EPA/625/7-88/003, July 1988). That docu-
ment has been superseded by the Facility Pollution Prevention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. Alu-
minum castings are machined and polished, and undergo chemi-
cal immersion, chromate conversion, and, in some cases,
painting. Steel castings are machined, heat treated, shot-
peened 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 eliminat-
ing the use of the absorbent socks by constructing containment
areas around the machines.
This Research Brief was developed by the principal investiga-
tors and EPA's National Risk Management Research Labora-
tory, 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.
* University of Tennessee, Department of Engineering Science and Mechanics
"University City Science Center, Philadelphia, PA
Introduction
The amount of waste generated by industrial plants has be-
come 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 manu-
facturing 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 participat-
ing plants. In addition, the project provides valuable experi-
ence for graduate and undergraduate students who participate
in the program, and a cleaner environment without more regu-
lations and higher costs for manufacturers.
-------
Methodology of Assessments
The pollution prevention opportunity assessments require sev-
eral 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 support-
ing technological and economic information is developed. Fi-
nally, 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 remain-
ing machined aluminum castings undergo a drag-through pol-
ishing 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 trans-
ported 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 harden-
ing. After heat treatment, the gears are quenched in an oil
tank.
The cooled heat-treated gears are shipped offsite to a "shot-
peening" 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 pro-
cess 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 re-
maining gears are packaged and shipped to dealers to be sold
as replacement parts.
Assembly
The finished component parts are mounted on racks and trans-
ported 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 Freon™ 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 opportuni-
ties, 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 preven-
tion 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. Environ-
mental Protection Agency. The EPA Project Officer was Emma
Lou George.
-------
Chrome
Conversion
Drying
\
Painting
?e/
ar
stings
Heat
^ •= — - Treating
Replacement
Parts Packaged
and Shipped
Offsite
Finished Product
Shipped to Sister
Plant for use in
Motor Units
Quenching
Offsite
Peening
Inspecting
Oiling
Leak
Testing
Deburring
Par
Match
i
ts
ing
Assembly
i
f
Hardware,
Parts
Figure 1. Abbreviated process flow diagram for gear case manufacture.
Table 1. Summary of Current Waste Generation
Waste Stream Generated
Cardboard
Soiled gloves
Hydraulic oil and coolant
Absorbent socks/oil
Aluminum dust sludge
Spent abrasive
Filter cake
Sludge filter cake
Methyl ethyl ketone/paint
Steel scrap
Vaporized liquid nitrogen
Methanol
Slurry stones
Filtered particulate metal
Wastewater
Source of Waste
Parts receiving
Various plant operations
Leaks from machines
Absorbing of leaked oil and
coolant from machines
Polishing
Drag-through polishing
Drag-through polishing
Wastewater treatment
Paint line cleaning
Machining
Heat treating
Heat treating
Deburring
Grinding
Various plant operations
Annual Quantity
Waste Management Method Generated (Ib/yr)
Shipped offsite to municipal landfill
Shipped offsite to municipal landfill
Shipped offsite to reclaimer
Shipped offsite as hazardous waste
Shipped offsite to municipal landfill
Shipped offsite to municipal landfill
Shipped offsite to municipal landfill
Shipped offsite as hazardous waste
Shipped offsite to fuels blending program
Shipped offsite
Vented
Vented
Shipped offsite to municipal landfill
Shipped offsite to municipal landfill
Treated onsite; sewered
95,180
4,160
188,000
17,640
913,680
28,000
1,152,000
13,200
740
63,900
4,982,200
126,590
8,900
76,800
34,997,000
Annual Waste
Management Cost ($/yr)
$360
20
12,230
14,370
3,410
100
4,300
7,480
2,410
7,410
0
0
30
290
28,580
-------
Table 2. Summary of Recommended Pollution Prevention Opportunities
Annual Waste Reduction
Pollution Prevention Opportunity
Waste Stream Reduced
Quantity
(Ib/yr)
Per Cent
Net Annual
Savings
Implementation Simple
Cost Payback (yr)
Construct a containment area around the Absorbent socks
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
mass and volume ofwastewater 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
to the municipal landfill and sell it to a re-
cycling company. Although this opportunity
will not lead to waste reduction, it will lead
to lower disposal costs and revenue for the
plant.
15,880
90
$ 13,150
$ 8,450
0.6
5,820
4,850
12,000
10,580
2.1
2.2
Note: Approximately 12,000 Ib/yr of waste oil/coolant will be collected and disposed of (at a much lower unit cost).
United States
Environmental Protection Agency
National Risk Management Research Laboratory (G-72)
Cincinnati, OH 45268
Official Business
Penalty for Private Use
$300
BULK RATE
POSTAGE & FEES PAID
EPA
PERMIT No. G-35
EPA/600/S-95/028
------- |