Environmental research brief: Pollution prevention assessment for a manufacturer of locking devices Page: 2 of 8
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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 (EPA162517-881003, 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.
This plant fabricates and finishes metal components which are
assembled into several types of locking devices. Approxi-
mately one million units are produced annually by this plant
during 5,880 hr/yr of operation.
The operations used by this plant are described below.
Component Parts Manufacturing
The major raw materials used by the plant include zinc die
castings and carbon and stainless steel, brass, and bronze in
bars, coils, and rods. Raw materials are moved by forklift to
the metal fabrication area where cutting, bending and shaping,
drilling, milling, screwing, and tapping operations are performed.
Prior to subsequent finishing operations, residual machining
lubricant is removed from the parts in one of two vapor
degreasers utilizing trichloroethylene. Contaminated trichloro-
ethylene is distilled onsite and reused.
After cleaning, the parts are processed in one of three ways.
Some of the steel parts are shipped offsite for heat treatment
and then returned to the plant for further processing. A portion
of the parts is placed into storage until needed for production at
a later time. The majority of parts which become external
locking device parts are buffed to improve their appearance,
either by hand or in an automatic system. Parts that have
been buffed are cleaned in a third vapor degreaser.
All parts except those made of stainless steel require a surface
coating. Most of the parts require one or more layers of
electroplating. The second major type of coating used is
electrostatic coating, and the third type is lacquer application to
After the necessary coating process is complete, the compo-
nent parts are transported to the assembly area where the
different locking devices are assembled and packaged.
Because the electroplating operations generate a significant
amount of waste they are described in more detail in this
Parts that are to be plated that have not been buffed are first
placed into vibratory devices for removal of any surface irregu-
larities. Those parts are then conveyed through a small vapor
degreaser, washed in a series of two wash tanks, and rinsed.
Three different plating lines are used by the plant. A small
quantity of special parts is plated in a small-scale hand-plating
line. Typical plating runs include chrome-or black chrome-,
bronze-, or brass-plating and hot water rinsing between each
plating stage and at conclusion.
Smaller parts that are used on the majority of the locking
devices are placed into barrels for plating in the barrel-plating
line. For corrosion protection, typical plating includes copper
striking and plating, dull and bright nickel plating, and chrome
plating with hot water rinsing between each stage and at a final
Larger parts are placed onto racks and mechanically carried
through the rack-plating line. These parts are plated with zinc,
copper strike and plating, bronze, brass, nickel, and chrome for
After parts have been processed through the appropriate plat-
ing line, they are removed from the conveying devices, allowed
to air dry, and carried to the assembly area.
An abbreviated process flow diagram for this plant is shown in
Existing Waste Management Practices
This plant already has implemented the following techniques to
manage and minimize its wastes.
- A filter press and a drying oven are used to reduce the volume
of hazardous wastewater treatment sludge shipped offsite.
- Each vapor degreaser is served by a distillation unit for the
recycle and reuse of spent trichloroethylene.
- Counterflow rinsing is used in the plating operations.
. Flow restrictors have been installed on the water removal
lines of the electroplating rinse tanks to reduce the volume of
" A compactor is used to reduce the volume of nonhazardous
solid waste shipped to the municipal landfill.
" Water-based coolant and cutting oil is removed from metal
shavings using a centrifuge and returned to the metal fabri-
" Scrap metal shavings are recycled offsite.
" Canvas coverings have been installed over the openings of
the vapor degreaser units to reduce evaporative losses of
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 annual treatment and disposal 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
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Jendrucko, R.J.; Hurst, B.T. & Looby, G.P. Environmental research brief: Pollution prevention assessment for a manufacturer of locking devices, report, August 1, 1995; United States. (https://digital.library.unt.edu/ark:/67531/metadc621702/m1/2/: accessed April 19, 2019), University of North Texas Libraries, Digital Library, https://digital.library.unt.edu; crediting UNT Libraries Government Documents Department.