United States
Environmental Protection
Agency
National Risk Management
Research Laboratory
Cincinnati, OH 45268
Research and Development
EPA/600/S-95/032 August 1995
ENVIRONMENTAL
RESEARCH BRIEF
Pollution Prevention Assessment for a Manufacturer of
Aircraft Landing Gear
Richard J. Jendrucko*, Susan D. Morton*, 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ment has been superseded by the Facility Pollution Prevention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 aircraft landing gear. Metal forgings undergo
machining operations to form the various components needed
to manufacture the landing gear. The resulting components are
heat treated offsite, chrome plated offsite, painted, and as-
sembled into the final product. The team's report, detailing
findings and recommendations, indicated that painting-related
wastes are generated in large quantities and that significant
cost savings could be realized by reactivating the currently
unused electrostatic paint spray system.
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
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 aircraft landing gear. It operates 24 hr/
day, year-round to produce over 300 landing gear units annu-
ally.
Manufacturing Process
The plant manufactures many different aircraft landing gear
components which are assembled into complete landing gear
units for various commercial and military aircraft models. Raw
materials used by the plant include steel, aluminum, and tita-
nium forgings, fasteners, and bushings. The basic processes
used by the plant are described below in more detail.
Machining
Steel, aluminum, and titanium forgings are inspected upon
receipt for acceptable quality. Forgings that fail inspection are
returned to the vendor. The acceptable forgings undergo ma-
chining operations—sawing, milling, grinding, drilling, boring,
reaming, turning, stamping, forging, and shaping—to achieve
the desired shape and dimension. After machining, the forgings
are sprayed with a protective oil coating that controls corrosion
until the forgings undergo grinding; an alkaline wash solution is
used to remove the oil coating before grinding.
After grinding, the forgings are honed and buffed to smooth
their surfaces; spray-washed with an alkaline cleaner; and
blown dry using compressed air. Another protective coating of
oil is applied to parts which are then stacked on pallets and
shipped offsite to a heat-treating facility.
Heat-treated parts are machined, honed, and deburred after
they are returned to the plant. The parts are cleaned, sprayed
with corrosion-preventing oil, and shipped offsite for hard-chrome
plating. The plated parts are placed in a temporary storeroom
or sent directly to painting and assembly after they are re-
turned to the plant.
Painting and Plating
Aluminum, nickel, and bronze bushings are pressed into the
forgings. Occasionally, touch-up plating is necessary on some
small parts. The touch-up plating is done on an in-house
plating line that consists of six separate tanks for cleaning,
rinsing, and plating. Following touch-up plating, the parts are
cleaned in a cold solvent-cleaning tank.
Next the parts are vapor-degreased and blown dry with com-
pressed air. In preparation for painting, plated surfaces on the
parts are masked with paper and tape to prevent plating in
those areas. A coat of primer pre-mix is then sprayed onto the
parts. The primed parts are transported through an electric
infrared drying oven. After the primer has cured, a finish coat of
paint is applied. The parts are then transferred into the drying
unit for final paint curing and placed in a circulating air cool-
down chamber. Lastly, a final layer of clearcoat is applied to all
parts.
After the painting process, a corrosion preventative is applied
to all unpainted surfaces and the parts are palletized and
transported to the assembly area.
Assembly
The landing gear components parts are de-masked and me-
chanically fastened together to produce complete assemblies.
All hydraulic parts are pressure-tested for oil leaks. Finished
units are sent to the packaging and shipping area.
An abbreviated process flow diagram for the production of
aircraft landing gear is shown in Figure 1.
Existing Waste Management Practices
This plant already has implemented the following techniques to
manage and minimize its wastes.
• Certain operations that generated 1,1,1-trichloroethaneand
perchloroethylene waste streams have been eliminated at
this plant.
• A separate employee committee is responsible for tracking
each waste stream in the plant. The goal of each committee
is a 10% reduction in quantity of waste generated.
• Cardboard and paper waste is recycled.
• Fluid evaporators are used to concentrate waste coolant,
thereby reducing the volume of waste shipped offsite.
• Many chemicals and solvents are purchased in bulk to
eliminate disposal of small non-reusable containers.
• Solid paint waste is compacted to reduce its volume before
it is shipped offsite.
• 1,1,1-trichloroethane is no longer used as a hand-washing
agent.
• The temperature of the vapor degreaser has been lowered in
order to reduce evaporative losses of 1,1,1-trichloroethane.
• A recycling unit has been installed in the paint spraying areas
to reclaim waste paint solvent.
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 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
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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.
Steel, Aluminum,
and Titanium Forgings
This research brief summarizes a part of the work done
under Cooperative Agreement No. CR-819557 by the Univer-
sity City Science Center under the sponsorship of the U. S.
Environmental Protection Agency. The EPA Project Officer
was Emma Lou George.
Offsite
Plating
Storage
Oil
Spray
Washing
Washing
Honing
and Buffing
Final
Grinding,
Honing, and
Deburring
Compressed
Air
Dry-off
Final
Machining
Oil
Spray
Offsite
Heat
Treating
Small Parts
From Storage
Large
Components
From Storage
Oil
Spray
Cold
Cleaning
Storage
Components From
Storage
Fastening
Testing
Packaging
Figurel. Abbreviated process flow diagram for manufacture of aircraft landing gear.
Table 1. Summary of Current Waste Generation
Waste Stream Generated
Scrap metal
Source of Waste
Machining
Waste Management Method
Sold to recycler
Annual Quantity
Generated (Ib/yr)
2,600,000
Annual Waste
Management Cost ($/yr)
$-10,460
(credit
received)
Waste coolant
Machining
Adsorbent/hydraulic and machining oil Leaks from machines
Hydraulic and machining oil Periodic machine oil changes
Abrasive waste Grinding
Paint liquid waste Painting
Solid paint waste Painting
Concentrated in evaporator; shipped
offsite to fuels blending program 20,000
Shipped offsite to controlled landfill 50,000
Shipped offsite to fuels blending program 20,000
Shipped offsite to landfill 88,000
Shipped offsite to fuels blending program 4,000
Incinerated offsite 1,500
40,380
22,280
19,060
2,270
15,780
13,720
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Table 1. (continued)
Waste Stream Generated
Spent 1,1,1-trichloroethane
Spent paint booth filters
Waste solvent blend
Empty paint containers
Plating liquid waste
Plating solid waste
Evaporated 1,1, 1-trichloroethane
Evaporated solvent blend
Evaporated paint solvent and thinner
Miscellaneous solid waste
Source of Waste
Vapor degreasing
Paint booths
Cleaning
Painting
Touch-up plating
Touch-up plating
Vapor degreasing
Cleaning
Painting
Various processes
Annual Quantity
Waste Management Method Generated (Ib/yr)
Shipped offsite for recycling
Incinerated offsite
Incinerated offsite
Shipped offsite for reconditioning
Shipped offsite for treatment and disposal
Incinerated offsite
Evaporates to plant air
Evaporates to plant air
Evaporates to plant air
Shipped offsite to landfill
3,000
1,100
1,500
1,800
6,000
400
55,080
34,800
900
362,000
Annual Waste
Management Cost ($/yr)
12,850
14,000
8,300
11,700
11,680
4,110
0
0
0
36,630
Table 2. Summary of Recommended Pollution Prevention Opportunities
Annual Waste Reduction
Pollution Prevention Opportunity
Waste Stream Reduced Quantity (Ib/yr)
Per Cent
Net Annual Implementation Simple
Savings ($/yr) Cost Payback (yr)
Spent paint booth filters
Evaporated
1,1,1-trichloroethane
Reactivate the currently unused electro-
static paint spray system in order to im-
prove the paint transfer efficiency.
Install plastic covers with roller tracks
on all four sides of the vapor degreas-
er tank with openings just large enough
for the cables used to suspend the com-
ponents to reduce evaporative losses of
1,1,1-trichloroethane.
Construct a containment area around the Adsorbent/hydraulic
bases of the metal working machines to and machining oil
collect waste oil. Use the available wet-
vacuum to collect the waste oil for dis-
posal
Utilize reusable thin plastic shielding in-
stead of paper to mask parts prior to the
spray-painting process.
Solid paint waste
360
49,570
45.0001
1,010
33
90
67
1
Approximately 8,000 Ib/yr of waste oil will be collected and disposed of (at a much lower unit cost)
$36,680
22,530
12,740
4,200
$ 5,500
6,960
16,750
2,500
0.2
0.3
1.3
0.6
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-95/032
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