4>EPA
United States
Environmental Protection
Agency
National Risk Management
Research Laboratory
Cincinnati, OH 45268
Research and Development
EPA/600/S-95/029 September 1995
ENVIRONMENTAL
RESEARCH BRIEF
Pollution Prevention Assessment
for a Manufacturer of Electrical Load Centers
Richard J. Jendrucko*, Todd M. Thomas*, 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ment has been superseded by the Facility Pollution Prevention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 electrical load centers. Raw materials,
including coiled sheet steel and coiled copper strips, polysty-
rene pellets, and miscellaneous fasteners, are used in metal-
working, injection molding, painting, and assembly operations.
The team's report, detailing findings and recommendations,
indicated that a large quantity of waste overflow rinse water is
generated and that significant cost savings could be achieved
by installing valves that will allow operators to turn off the flow
during periods of nonuse.
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.
Introduction
The amount of waste generated by industrial plants has be-
come an increasingly costly problem for manufacturers and an
* University of Tennessee, Department of Engineering Science and Mechanics
** University City Science Center, Philadelphia, PA
Printed on Recycled Paper
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
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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 electrical load center housings for use
in residential and commercial buildings. It operates 6,000 hr/yr
to produce over one-million units annually.
Manufacturing Process
Electrical load center housings are manufactured by this plant
from raw materials including coiled sheet steel stock and coiled
copper strips, polystyrene pellets, and miscellaneous fasten-
ers. The major operations performed by the plant are metal
working, injection molding, painting, and assembly.
Metal Working
Metal housing boxes are fabricated from either cold-rolled steel
or galvanized steel received at the plant in coils. After inspec-
tion, coils are transferred to impact cutting operations in which
the steel is sheared into flat patterns and then sent to box-
forming operations.
Next, the cut patterns are loaded into the die of a large press
that punches hole patterns which provide inlets or outlets for
electrical wiring into the metal sheets. Then the metal pieces
are formed into a box shape using another press. Box corners
are spot-welded for reinforcement. Finished boxes undergo
inspection, and those that pass are transported to the
electrocoating painting operation. Defective boxes are shipped
offsite for recycling.
Copper electrical contacts used in the internal components of
the finished product are also manufactured onsite. Copper
strip rolls are inspected and transferred to cutting operations.
Appropriately cut copper pieces are dropped onto a chain
conveyor and transported through a gas-fired heat-treatment
oven. After heat treatment, about 20% of the parts are sent
offsite to be nickel plated. Parts that have been plated are
fastened to plastic parts manufactured onsite to form sub-
assemblies. Unplated copper parts are stored until needed in
final assembly.
Injection Molding
Various plastic structural pieces that are used to hold electrical
contacts and switches in place are manufactured onsite using
injection molding machines. Polystyrene pellets are vacuum-
conveyed to a feed hopper above the injection molding ma-
chine. The pellets are metered into the machine's heated
barrel in the appropriate quantity.
Inside the molding machine, plastic is melted and injected
under high pressure into a separable cavity-mold. Once the
cavity is filled with molten plastic, the mold is allowed to cool,
thus hardening the plastic into the desired shape. After plastic
solidification, the mold opens allowing the formed parts to drop
onto a conveyor belt. After storing 95% of the parts until
needed in final assembly, the remaining parts are shipped
offsite for the production of subassemblies used in the final
products.
Electrocoating
Metal boxes are painted using a cathodic electrocoating sys-
tem in which resinous materials containing pigments in a water
suspension are deposited on the part's surface using an elec-
tric potential difference. Because this paint system is a form of
electrocoating, boxes must be thoroughly washed and rinsed
to remove contaminants prior to coating.
The metal boxes are conveyed through the following tanks in
sequential order:
• heated dilute potassium hydroxide solution spray-wash for
removal of surface particulates and oils
• clean water rinse
• heated dilute phosphorous solution spray-wash for etching of
the metal
• clean water rinse
• deionized water wash
• paint solution
• deionized water rinse to remove residual paint solution
• surfactant solution rinse to facilitate water drainage
Painted boxes are conveyed through a gas-fired oven for
curing. After the boxes exit the oven, they are cooled and
inspected. Those boxes that pass inspection are transferred
into storage to await final assembly.
Final Assembly
Final assembly of the electrical load centers consists of instal-
lation of component parts, such as breakers and switches, into
painted steel housings on an automated-robotic assembly line
and manual installation of internal and external components
that require part manipulation not suitable for robots.
An abbreviated process flow diagram for the production of
electrical load centers is shown in Figure 1.
Existing Waste Management Practices
This plant already has implemented the following techniques to
manage and minimize its wastes.
• Waste computer paper is collected and recycled.
• The use of chlorinated cleaning solvents has been elimi-
nated.
• Wooden pallets are repaired and reused.
• Copper and steel scrap are recycled.
• Self-adhering labels are used on the load centers in order to
eliminate the use of glue.
Pollution Prevention Opportunities
The type of waste currently generated by the plant, the source
of the waste, the waste management method, the quantity of
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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 need for less raw material
and from reduced present and future 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 em-
ployee health. It also should be noted that the savings given
for each opportunity reflect the savings achievable when imple-
menting each pollution prevention opportunity independently
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.
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Ftgura 1. Abbreviated process flow diagram for electrical load center manufacture.
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United States
Environmental Protection Agency
National Risk Management Research Laboratory (G-72)
Cincinnati, OH 45268
Official Business
Penally for Private Use
$300
BULK RATE
POSTAGE & FEES PAID
EPA
PERMIT No. G-35
EPA/600/S-95/029
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