&EPA
United States
Environmental Protection
Agency
Risk Reduction
Engineering Laboratory
Cincinnati, OH 45268
Research and Development
EPA/600/M-91/018 Jul. 1991
ENVIRONMENTAL
RESEARCH BRIEF
Waste Minimization Assessment for a
Manufacturer of Brazed Aluminum Oil Coolers
F. William Kirsch 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 hazardous waste but
lack the expertise to do so. Waste Minimization Assessment
Centers (WMACs) were established at selected universities
and procedures were adapted from the EPA Waste Minimiza-
tion Opportunity Assessment Manual(EPA/625/7-88/003, July
1988). The WMAC team at the University of Tennessee in-
spected a plant manufacturing brazed aluminum oil coolers
that are used in heavy equipment. After the cooler components
are fabricated, they are degreased (with Chlorothenet, which is
recycled); assembled; brazed to join internal and external coil
fin surfaces (involving a molten salt bath and a quench tank
whose sludge is disposed of on-site in a sand filter bed);
cleaned (with solutions and rinse waters needing treatment
and disposal); and painted. The team's report, detailing find-
ings and recommendations, indicated that a significant minimi-
zation opportunity could be effected by replacing molten salt
bath brazing with vacuum brazing. The implementation cost
would be high and the payback years relatively long, but the
percent waste reduction (80%) and annual savings would be
pronounced.
This Research Brief was developed by the principal investiga-
tors and EPA's Risk Reduction Engineering Laboratory, Cin-
cinnati, OH, to announce key findings of an ongoing research
* University City Science Center, Philadelphia, PA 19104.
f Mention of trade names or commercial products does not consti-
tute endorsement or recommendation for use.
project that is fully documented in a separate report of the same
title available from the authors.
Introduction
The amount of hazardous 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 hazardous waste 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 formation of hazardous waste but
who lack the inhouse 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 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 hazardous 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 $50 million, employ no more than
500 persons, and lack inhouse expertise in waste minimization.
The potential benefits of the pilot project include minimization
of the amount of waste generated by manufacturers, reduced
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waste treatment and disposal costs for participating plants,
valuable experience for graduate and undergraduate students
who participate in the program, and a cleaner environment
without more regulations and higher costs for manufacturers.
Methodology of Assessments
The waste minimization assessments require several site visits
to each client served. In general, the WMACs follow the proce-
dures outlined in the EPA Waste Minimization Opportunity
Assessment Manual (EPM625f7- 88/003, July 1988). The WMAC
staff locates the sources of hazardous waste in the plant and
identifies 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
The plant manufactures aluminum brazed oil coolers for use in
heavy equipment. The plant produces approximately 60,000
units each year.
Manufacturing Process
The raw materials used in the production of the oil coolers
include aluminum in sheet and coil form, aluminum castings and
extrusions, tubes, fittings, brackets, caution labels, and plastic
plugs.
The following steps are involved in the production:
• Shearing, punching, and forming operations to
fabricate the oil cooler tanks, headers, air fins,
sides, and oil turbulator fins.
Degreasing oil cooler tanks, headers, sides, fit-
tings, and brackets. The solvent Chlorothene (95%
1,1,1- trichloroethane) is used in an open-air,
steam-heated vapor degreaser. The unit is
equipped with a refrigeration unit that condenses
Chlorothene vapor and minimizes evaporative
losses to surrounding plant air.
Recycling of spent Chlorothene to the degreasing
operation with the use of an on-site still. Chlo-
rothene is continuously circulated between the
degreaser and a steam-heated solvent recovery
still. Still bottoms containing spent Chlorothene,
water, and oil are shipped off-site as hazardous
waste.
Assembling oil coolers.
Brazing assembled oil coolers to join the internal
and external coil fin surfaces for enhanced heat
transfer. The oil coolers are first preheated in
a gas-fired oven at 1020° F for 15 min. After they
are dipped into an electrically heated molten salt
bath containing a sodium- chloride-based com-
pound, lithium chloride, and aluminum fluoride for
1.5 min at 1128°F, they are dipped in a water
quench tank. Sludge from the salt bath and quench
tanks is disposed of in the on-site sand filter bed.
Solids remaining in the filter are landfilled on
company property; water is fed to the settling pond
and eventually discharged to a river.
Cleaning oil coolers to remove all residual salt, to
expose copper cells (which could cause corrosion
failure), and to condition metal surface before
painting. The following steps are involved
in the cleaning:
- submersion in a 2% nitric acid bath (1 to 2 hr
residence time),
- cold water rinse,
- dipping in NaOH caustic soda etching solution,
- hot water (102°F) rinse,
- cold water rinse,
- dipping in a 50% nitric acid bath,
- two cold water rinses,
- dipping in a chromic acid wash,
- two deionized water rinses, and
- drying in a natural gas-fired oven.
Treating hazardous spent process solutions and
contaminated rinse water streams. The liquids are
treated in a neutralization tank with lime for pH
control and f locculant to enhance removal of sus-
pended solids. The solution leaving the tank is
pumped to a clarifier that removes solids and
allows filtered water to flow to the settling pond. A
solids-rich stream is pumped to a sludge-thicken-
er settling tank for secondary sedimentation. Su-
pernate from the settling tank is transferred to the
sand filter beds for final water removal before on-
site landfilling of solids.
Treating of effluent from the chromic acid and
deionized rinse water washes. Because these
hazardous waste streams contain chromium in
hexavalent form, they are treated to obtain a
sludge containing less toxic trivalent chromium
compounds. Several chemical agents are added
to the waste to produce relatively insoluble com-
pounds that are recovered on the sandfilter beds
and disposed of in the landfill. The liquid is pumped
to the settling pond and is eventually released to
the river.
Painting oil coolers. The coolers are dipped in a
paint-filled tank, allowed to drip after immersion,
and transferred to a spray booth for additional
spray painting. Paint is collected on floor cover-
ings (plastic sheet or cardboard) and in spray
booth filters and is disposed of daily in barrels,
which are sent to an off-site landfill.
Existing Waste Management Practices
The plant has taken the following steps in managing its
hazardous wastes.
The plant owns and operates a landfill for its
private use.
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Chromium is reduced from the hexavalent to
the trivalent form in-house.
A refrigeration unit and a solvent recovery still
have been added to the degreasing unit to
minimize evaporative loss and liquid waste.
The plant constantly monitors its waste stream
effluents and has installed its own hazardous
waste treatment facility.
Water-based paints are currently used.
A designated professional staff person, based
at corporate headquarters, periodically visits
satellite plant locations to provide assistance in
both hazardous waste monitoring and manage
ment techniques.
Waste Minimization Opportunities
The type of waste currently generated by the plant, the source
of the waste, the quantity of the waste, and the annual treatment
and disposal costs are given in Table 1.
Table 2 shows the opportunities for waste minimization that the
WMACteam recommended for the plant. The type of waste, the
minimization opportunity, the possible waste reduction and
associated savings, and the implementation cost along with the
payback time are given in the table. The quantities of hazardous
waste currently generated by the plant and possible waste
reduction depend upon the production level of the plant. All
values should be considered in that context.
It should be noted that the economic savings of the minimization
opportunity, in most cases, result from the need for less raw
material and from reduced present and future costs associated
with hazardous 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 should also be noted that the savings given
for each opportunity reflect the savings achievable when imple-
menting each opportunity independently and do not reflect
duplication of savings that would result when waste minimiza-
tion opportunities are implemented in a package.
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. Environmen-
tal Protection Agency, the EPA Project Offficer was Brian A.
Westfall.
The EPA contact, Emma L. George, can be reached
at:
Pollution Prevention Research Branch
Risk Reduction Engineering Laboratory
U.S. Environmental Protection Agency
Cincinnati, OH 45268
Table 1. Summary of Current Waste Generation
Waste Generated
Source of Waste
Annual
Quantity Generated
Annual Wast
Management Cost
Still bottoms containing spent,
contaminated Chlorothene (95%-
1,1,1 -trichloroethane), water,
and oil
Evaporation of Chlorothene
Sludge containing compounds
derived from the salt bath con-
stituents, impurities from the
baths, and contaminants on the
products' surfaces
Sludge containing various solids
from the treatment of the spent
cleaning solutions
Sludge containing various com-
pounds from the chromium reduc-
tion process
Paint-contaminated filters and
cardboard and plastic sheets
On-site solvent recycing still associated with 150 gal
the degreasing operation.
Degreasing operation 6,520 gal
Salt bath tank and water quench tank in the 514,920 Ib
brazing process. The sludge is collected on
the sand filter beds.
Treatment process for spent solutions from 1,171,060 Ib
the cleaning of the brazed product. The
sludge is collected on the sand filter beds.
Chromium reduction process. The sludge is 88,940 Ib
collected on the sand filter beds.
Painting of product. 9,81 Olb
$4,650
O1
28,500
36,380
16,500
13,480
1 Currently the plant reports no waste management costs associated with the evaporation of Chlorothene.
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Table 2. Summary of Recommended Watte Minimization Opportunities
Annual Waste Reduction
Waste Generated
Minimization Opportunity Quantity
Percent
Net Annual Implementation Payback
Savings Cost Years
Evaporation of Chlorothene
from the degreaser unit
Still bottoms from the
on-site solvent recycling
still
Evaporation of Chlorothene
and Chlorothene contained
in the still bottoms
Sludge from the water
quench tank in the
brazing process
Sludge from the salt
bath and water quench
tanks in the brazing
process
Paint-contaminated
cardboard and plastic
sheets
Paint-contaminated
filters and cardboard
and plastic sheets
Install a conveniently re- 3,260 gal 50
movable cover on the vapor
degreaser tank to reduce
evaporative losses. Cover
the tank except when parts
baskets are being lowered
into or taken out of the tank.
Reduce the amount of lubri- 30 gal 20
cants used during metal-
working and reduce the open-
ness of machine work areas
to decrease the amount of
oil picked up by parts during
processing, thereby minimi-
zing the amount of degreasing
required.
Replace the vapor de- 6,600 gal 99
greaser system with an
ultrasonic cleaning system
that uses biodegradable
detergents.
Modify the procedure for 23,170 Ib 4
dipping the coolers in the
salt bath to minimize carry-
over to the water quench
tank. Achieve maximum
salt removal by gently vi-
brating or shaking the parts
baskets and subjecting the
parts to a hot air blast.
Replace molten salt bath 411,930 Ib 80
brazing with vacuum bra-
zing. Vacuum brazing is
suitable for 80% of this
plant's products.
Reduce paint loss by 2,180lb 22
installing a low-pressure
air-jet system over the paint
dipping area to blow excess
paint downward into tank.
Install an IR paint-drying
lamp to prevent dripping
when coolers are moved
to the spray booth area
Install an electrostatic spray 3,510 Ib 36
paint system for applying the
oil cooler second coat of
paint to reduce overspray
loss.
Discontinue the practice of 4,910 Ib 50
painting oil coolers that
will be repainted by the
customer. Vacuum seal the
oil coolers to provide corrosion
protection.
$17,180'
$220 0.01
1.0101
290 0.3
20.4502
20.5203
50,000
43,880
2.4
2.1
203.4403
4,350*
720,640
2,490
3.5
0.6
11.2004
59.7204
13,200
1.2
28,440 0.5
1 Includes cost savings because less Chlorothene purchased.
2 Total savings have been reduced by the cost of detergents required.
3 Includes cost savings because less salt bath constituents purchased.
4 Includes cost savings because less paint supplies purchased.
&U.S. GOVERNMENT PRINTING OFFICE: I«WI - 548-028/40034
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United States Center for Environmental Research BULK RATE
Environmental Protection Information POSTAGE & FEES PAID
Agency Cincinnati OH 45268 EPA PERMIT NO. G-35
Official Business
Penalty for Private Use $300
EPA/600/M-91/018
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