SEPA
United States
Environmental Protection
Agency
Research and Development
Risk Reduction
Engineering Laboratory
Cincinnati, OH 45268
EPA/600/S-92/029 Sept. 1992
ENVIRONMENTAL
RESEARCH BRIEF
Waste Minimization Assessment for a
Manufacturer of Cutting and Welding Equipment
Harry W. Edwards", Michael F. Kostrzewa*. 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). The WMAC
team at Colorado State University performed an assessment at
a plant that produces custom-built cutting and welding equip-
ment. Components are fabricated from steel and other raw
materials that are cleaned, machined, welded, and painted.
Machines are then assembled, tested, and calibrated. The
hazardous wastes generated by the plant include tramp oil,
spent cutting fluid, spent lacquer thinner, and chromium-con-
taminated paint dust and filters. The team's report, detailing
findings and recommendations, indicated that the plant could
achieve the greatest dollar savings by replacing chromium-
containing solvent-based paints with chromium-free water-based
paints.
This Research Brief was developed by the principal investiga-
tor and EPA's Risk Reduction Engineering Laboratory, Cincin-
nati, OH, to announce key findings of an ongoing research
project that is fully documented in a separate report of the
same title that is available from University City Science Center.
Introduction
The amount of waste generated by industrial plants has become
an increasingly costly problem for manufacturers and an addi-
' Colorado State University, Department of Mechanical Engineering
" University City Science Center, Philadelphia, PA
tional stress on the environment. The primary solution to the
problem of waste is to reduce or eliminate it 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 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 Colorado State University's
(Fort Collins) WMAC. The assessment teams have considerable
direct experience with process operations in manufacturing
plants and also have the knowledge and skills needed to
minimize 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 $75 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 and re-
duction of waste treatment and disposal costs for participating
plants, in addition, the project provides 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 folbw the pro-
cedures outlined in the EPA Waste Minimization Opportunity
Assessment Manual (EPA/625/7-88/003, July 1988). The
Printed on Recycled Paper
-------
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 supporting
technological and economic information is developed. Finally,
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 custom-built welding equipment and
cutting machines. It operates approximately 4,500 hr/yr to pro-
duce more than 80 machines annually.
Manufacturing Process
This plant produces welding equipment and cutting machines
that are custom-built to meet clients' requirements. The major
raw material is steel; however, iron, aluminum, brass, zinc-
plated steel, and phenolic materials are also used.
Prior to fabrication, the metals are cleaned using a spray wand
to remove residual rust-preventing oil. A flame cutter is then
used to cut the metal to workable dimensions. The material
undergoes machining with drills, lathes, and cutting and milling
machines. The parts are then mechanically cleaned using
grinders and sanders. Welding is performed as necessary.
Components to be painted are first treated with alkaline cleaner
and phosphate solution in a series of dip tanks. Solvent-based
acrylic lacquers and enamels are applied using spray guns in
the paint booth. Logos are applied using silk-screening.
The various components are then assembled, tested, and
calibrated. An abbreviated process flow diagram that also de-
scribes waste generation is shown in Figure 1.
Existing Waste Management Practices
This plant has already implemented the following techniques to
manage and minimize its wastes.
• A portable oil skimmer is used to remove tramp oil from
the cutting fluid in the sumps of the computer numerically-
controlled (CNC) machines. The decreased amount of
tramp oil in the sumps has increased the life of the cutting
fluid.
• A belt skimmer and filter are used to remove tramp oil and
paniculate matter from the cutting fluid drained from the
CNC machines so that the fluid can be reused in the
manual machining equipment.
• The phosphating dip line used prior to painting was in-
stalled to reduce the use of lacquer thinner for cleaning
and degreasing.
• Electronic assemblies are cleaned with a terpene hydro-
carbon cleaner instead of perchloroethylene.
• High-volume low-pressure paint guns are used in order to
reduce overspray and conserve paint.
• Water-based paints are being evaluated on a trial basis as
a replacement for the solvent-based paints currently used.
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 treat-
ment and disposal costs are given in Table 1.
Table 2 shows the opportunities for waste minimization that the
WMAC team 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 times 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 minimization
opportunity, 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 quantifi-
able 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
implementing each waste minimization opportunity independently
and do not reflect duplication of savings that may result when
the opportunities are implemented in a package.
Additional Recommendations
In addition to the opportunities recommended and analyzed by
the WMAC team, additional measures were considered. These
measures were not completely analyzed because of insufficient
data, minimal savings, implementation difficulty, or a projected
lengthy payback. Since one or more of these approaches to
waste reduction may, however, increase in attractiveness with
changing conditions in the plant, they were brought to the
plant's attention for future consideration.
• Test the waste cutting fluid from the CNC machines to
determine if the lead and benzene concentrations are low
enough that the waste could be shipped to a disposal
facility for nonhazardous waste.
• Evaluate the need for the application of rust-preventive oil
to the raw material. It is possible that the rust-preventive
oil is unnecessary thereby reducing the need for cleaning.
• Segregate the scrap metal by type to increase the amount
of revenue received.
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 Officer was Emma Lou
George.
-------
Steel, Iron,
Zinc-Plated Steel,
Aluminum, Brass,
Phenolic Materials
Cleaning
- Water Spray
Wastewater to Sand/Oil
Interceptor and Sewered
Machining
- Flame-Cutting
- Drilling, Cutting
- Milling
^ Tramp Oil and Spent
Cutting Fluid Incinerated
\Offsite
(Waste Oils foN
\ Reclaimer J
Mechanical Cleaning
- Debarring & Polishing
Slag and Grinder
Dust Accumulating
Onsite
Painting
- Pro- Treatment
- Spray-Painting
- Silkscreen Painting
Waste Aqueous
Cleaner Accumulating
Onsite
Final Assembly
- Testing
- Calibration
Paint Dust and Filters.
Waste Thinner, and
Equipment Cleaner
Incinerated Off site
Wastewater to Sand/Oil
Interceptor and Sewered
Slag Accumulating Onsite
Jnsitej
Figure 1. Abbreviated process flow diagram.
-------
Table 1. Summary of Current Waste Generation
Waste Generated
Source of Waste
Annual Quantity
Generated
Annual Waste
Management Cost
Wastewater
Wastewater
Tramp oil
Spent cutting fluid
Miscellaneous waste oil
Slag and grinder dust
Scrap metal
Wastewater
Waste aqueous degreasers
Spent lacquer thinner
Equipment cleaning solvent
Chromium-contaminated
paint dust and filters
Wastewater
Slag
Spray wand phosphating/cleaning.
Wastewater from the removal of rust-
preventing oil from metal prior to
fabrication is drained to a sand and
oil interceptor and then sewered as
industrial wastewater.
Flame cutting.
Cooling water that is used to prevent
metal warping during flame cutting
is drained to a sand and oil interceptor
and then sewered as industrial wastewater.
Machining.
Tramp oil from cutting fluid is shipped
off site for incineration at a hazardous
waste disposal facility.
Machining.
Cutting fluid that cannot be reused is
shipped offsite for incineration at a
hazardous waste disposal facility.
Various plant equipment.
Waste motor oil and lubricating oil from
forklifts and other plant equipment is
shipped offsite for reclamation as industrial
boiler fuel.
Machining.
Slag resulting from flame cutting and
grinding dust are accumulating onsite.
Machining
Scrap metal generated by sawing and
machining operations is sold to a recyder.
Paint line pretreating.
Water used for pretreating prior to painting
is drained to a sand and oil interceptor and
then sewered as industrial wastewater.
Paint line pretreating.
Waste aqueous cleaners used in small
volumes are stored onsite pending
analysis and determination of a proper
disposal method.
Painting.
Lacquer thinner used to degrease parts
prior to painting is shipped offsite for
incineration at a hazardous waste disposal
facility.
Painting.
Solvent used to clean paint guns and other
painting equipment is shipped off site for
incineration at a hazardous waste disposal
facility. (This solvent is no longer used; it
has been replaced by the lacquer thinner.)
Painting.
Paint fitters that trap overspray and paint
dust are shipped offsite for incineration at
a hazardous waste disposal facility.
Assembly and testing.
Cooling water used in flame cutting testing
is drained to a sand and oil interceptor and
then sewered as industrial wastewater.
Assembly and testing.
Slag resulting from flame cutting testing is
accumulating onsite.
210,000 gal
437,500 gal
495 gal
420 gal
400 gal
Not available
Not available
23,000 gal
Not available
810 gal
95gal
1,390lb
3,180 gal
Not available
1500'
f,040'
2,310
1960
80
0*
Not available.
60'
0*
4,430'
5/0'
5,670
10'
0*
'Includes cost of raw material.
'Accumulating onsite; no waste management costs incurred.
-------
Table 2. Summary of Recommended Waste Minimization Opportunities
Waste Generated
Chromium-contaminated
paint dust and filters
Spent lacquer thinner
Minimization Opportunity
Replace chromium-containing
solvent-based paints with
chromium-free water-based paints.
Paint dust and filters can then be
disposed of in the municipal
landfill without an increase in
trash hauling fees. The purchase
of lacquer thinner and the
subsequent disposal of spent
thinner will be reduced.
Annual Waste Reduction Net Implementation
Quantity Percent Annual Savings Costs
1,390lb 100 $4,1 80 ' $1,000
40 gal 5
Payback
Years
0.2
Spent lacquer thinner
Spent cutting fluid
Spent cutting fluid
Spent cutting fluid
Install a distillation unit to recover 610 gal 75
lacquer thinner for reuse. The
amount of spent thinner shipped
off site for disposal and the
amount of lacquer thinner
purchased will be reduced.
Acid treat the cutting fluid waste 240 gal 57
from the CNC machines to effect
a separation of organic and aqueous
phases. Discharge the aqueous phase
to the industrial sewer and dispose
of the organic phase at a hazardous
waste disposal facility.
Heat the cutting fluid waste from 240 gal 57
the CNC machines to evaporate
the aqueous phase and reduce
the volume of waste sent to the
offsite hazardous waste disposal
facility.
Replace the cutting fluid used in 150 gal 36
the track mill with a vegetable oil-
based spray coolant that is bio-
degradable and completely
consumed during cutting.
2,300**
7,060
3.1
1,100s
1,000
0.9
1,070'
2,800
2.6
7703
1,210
1.6
1 Total waste management cost savings have been reduced by increased raw material costs.
'Total waste management cost savings have been reduced by the operating cost of the proposed system.
'Includes savings on raw materials.
&U.S. GOVERNMENT PRINTING OFFICE: t*94 • 5SO-O67/80I55
-------
------- |