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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. Waste Minimization Assessment Centers (WMACs) were established at selected universities and

procedures were adapted from the EPA Waste Minimization

Opportunity Assessment Manual (EPA/625/7-88/003, July 1988).

That document has been superseded by the Facility Pollution

Prevention Guide (EPA/600/R-92/088, May 1992). The WMAC

team at the University of Louisville performed an assessment

at a plant that manufactures iron castings and fabricated sheet

metal parts. Foundry operations include mixing and mold formation, core making, metal pouring, shakeout, finishing, and

painting. Cutting, shaping, and welding are the principal metal

fabrication operations. The team’s report, detailing findings and

recommendations indicated that paint-related wastes are generated in large quantities, and that significant waste reduction

and cost savings could be realized by installing a dry powder

coating system or by replacing conventional air spray paint

guns with high-volume low-pressure spray guns.

This research brief was developed by the principal investigators and EPA’s National Risk Management Research Laboratory, 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 become an increasingly costly problem for manufacturers and an

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

Louisville’s 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 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 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 pollution prevention opportunity assessments require several site visits to each client served. In general, the WMACs

Waste Minimization Assessment for a Manufacturer of Iron Castings

and Fabricated Sheet Metal Parts

United States

Environmental Protection

Agency

National Risk Management

Research Laboratory

Cincinnati, OH 45268

ENVIRONMENTAL

RESEARCH BRIEF

Research and Development EPA/600/S-95/008 August 1995

Marvin Fleischman*, Jennifer J. Harris*, Allan Handmaker*,

and Gwen P. Looby**

* University of Louisville, Department of Chemical Engineering

** University City Science Center, Philadelphia, PA

E AP
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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 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 performs casting of gray iron and ductile iron, fabricates heavy metal plate parts, and fabricates sheet metal

parts. It operates 4,000 hr/yr to cast approximately 25,000 tons

of metal and fabricate over 4 mil ft2 of metal annually.

Manufacturing Process

Foundry Operations

Three basic departments—large moldings, medium moldings,

and small moldings—make up the foundry. Mixing and mold

formation, core making, metal pouring, shakeout, finishing, and

painting operations take place in each of the three departments.

Patterns produced onsite are made from wood boards and are

used to form the sand molds for casting. Saws, planes, drills,

sanders, band-saws, and a press are used to shape the wood.

Sand that is used to form the molds and cores is mixed with a

binding agent so that the sand will set into a mold. The sand is

then pumped into the pattern, compacted, and allowed to

harden. Small, molded spacers called cores are made onsite in

a similar manner.

Metals used include virgin pig iron, old rails, and purchased

slitter scrap (from metal cutting). In addition, all of the internally

generated scrap metal is remelted and reused. No metal pretreatment is performed prior to melting. Weighed amounts of

metal are placed in one of three electric induction furnaces.

Once the metal is placed in the furnace, some alloying agents

are added. As the metal melts, slag (impurities and dirt) separates from the metal and is skimmed off. After the metal leaves

the furnace, silicon and other alloying agents are added to

produce either gray cast iron or ductile iron.

The melted metal is collected in ladles and transported via

crane to the assembled mold and poured. The mold is then

allowed to cool.

After the metal has cooled, the mold is moved to the shakeout

(a large vibrating metal grating). The vibration causes the

casting to separate from the sand mold. If necessary, employees dig the sand core out of the casting. Remaining sand is

removed from the casting surface with steel shot. Some of the

castings are painted before they are shipped.

An abbreviated process flow diagram for the foundry operations is shown in Figure 1.

Metal Fabrication Operations

Heavy metals fabrication operations include cutting, shaping,

and welding plates of low carbon steel from 3/8 to 8 in. thick.

Parts requiring painting are sent offsite and returned.

The light metals fabrication department produces metal cabinets and similar products from 4 by 8 ft sheets of 1/4 in. or

smaller thickness. After metal shaping operations, oil present

on the sheets is removed using a mixture of phosphoric acid

and steam.

All parts fabricated in this area receive a primer coat and 90%

of products receive a topcoat onsite.

An abbreviated process flow diagram for the metal fabrication

operations is shown in Figure 2.

Existing Waste Management Practices

This plant already has implemented the following techniques to

manage and minimize its wastes.

• All scrap metal generated in the foundry operations is remelted and reused.

• The plant recently replaced the binder used to make large

molds with one that does not contain methanol.

• Sand from the molds is collected and reused.

• High-volume low-pressure paint spray guns are used for

large painting jobs.

• Onsite painting is limited in order to control volatile organic

compound (VOC) emissions.

• Pallets received with raw material shipments are reused for

shipping products.

• Sand used for making molds contains a lesser amount of

chromium than the sand used previously.

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 opportunities, in most cases, results from the need for less raw material

and from reduced present and future costs associated with
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Figure 2. Abbreviated process flow diagram for fabrication operations.

Figure 1. Abbreviated process flow diagram for foundry operations.

New Metal

Pre-heating

Melting in

electric

induction

furnace

Transporting

in

ladles

Rejected

castings

New Sand Patterns

Mixing

Core and

mold

formation

Core wash

coating

Pouring

and

cooling

Shakeout

Sand

reclamation

Accepted

castings

Discards

Gate/riser

knock-off

Grinding

and

blasting

Cleaning

and

washing

Painting

Finished castings

Shipped to customers

Metals Metal working

Offsite painting

Steam cleaning

Heavy metal parts shipped

Air

drying

Priming

Oven drying

Light metal

parts shipped

Top-coating

Light metal

parts shipped

Oven drying
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Table 1. Summary of Current Waste Generation

Waste Stream Generated Source of Waste Waste Management Method Annual Quantity Annual Waste

Generated (lb/yr) Management Cost

Empty drums and totes Raw material receiving Reconditioned or recycled offsite 52,200 $2,720

Pallets and scrap wood Raw material receiving Recycled offsite 200,000 3,950

General trash Various operations Shipped to landfill 75,240 9,740

Paint and solvent wastes Painting operations Shipped to fuels program 89,350 25,250

Dirt slag and waste sand Metal preparation and foundry operations Shipped to landfill 8,720,000 49,270

Metal scrap Metal fabrication Sold to recycler 4,132,000 -92,160

Dirt and broken refractory Metal charging and metal pouring Shipped to landfill 868,000 13,080

Waste acid and binder Cleaning of storage tanks Disposed of as hazardous waste 1,080 800

Waste corewash Cleaning of dip tank Shipped to landfill 13,,200 500

Chromium emissions Emitted from sand Vented from plant 600 0

Spent shot and sand Removal of molds and cores Shipped to landfill 400,000 3,540

Metal and sand dust Shakeout and finishing Shipped to landfill 130,620 2,740

Fugitive emissions Painting Evaporated to plant air 7,200 0

VOC emissions Painting Evaporated to plant air 43,000 0

Paint solids Painting (filtered from water) Shipped to fuels program 825 300

Exhaust filters and paint overspray Paint booth Shipped to landfill 43,650 1,000

Air intake filters Paint booth Shipped to landfill 1,250 12,000

Wastewater Various operations Treated onsite; sewered 13,694,280 1,730

Wastewater treatment sludge Onsite wastewater treatment Shipped to landfill 134,000 10,400

Waste oils Maintenance of machinery Recycled offsite 4,680 0

Office waste Office operations Shipped to landfill 40,000 3,150

Sanitary wastewater Plant and office Sewered 5,404,320 630

Spent solvent Parts washer Removed by supplier 2,060 2,420

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 also should be noted that the savings given for

each opportunity reflect the savings achievable when implementing each pollution prevention 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, several additional measures were considered. These measures were not analyzed completely because

of insufficient data, implementation difficulty, or a projected

lengthy payback. Since these approaches to pollution prevention may, however, increase in attractiveness with changing

conditions in the plant, they were brought to the plant’s attention for future consideration.

• Install a sewer meter to measure the volume of wastewater

discharged to the sewer. Current sewer charges are based

on the amount of water that enters the plant.

• Explore the possibility of shipping sawdust to an area nursery

or to a local cement or brick kiln.

• Give scrap wooden crates and pallets to employees for use

as kindling.

• Use the scrap metal from machining and trimming operations

in the sheet metal shop in the foundry operations. Use of the

scrap metal would require removal of the rust-preventing oil

from its surface.

• Recycle waste cardboard and paper sacks.

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. Environmental Protection Agency. The EPA Project Officer was Emma

Lou George.
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Table 2. Summary of Recommended Pollution Prevention Opportunities

Annual Waste Reduction

Pollution Prevention Opportunity Waste Stream Reduced Quantity Per Cent Net Annual Implementation Simple

(lb/yr) Savings Cost Payback (yr)

Use an aqueous-based parts washer to replace the solventbased rental unit. The recommended unit uses a biodegradable detergent, automatic parts washing action, and a dirty -

water evaporator. The small quantity of sludge generated by

the proposed washer (720 lb/yr) can be disposed of as nonhazardous waste. Spent solvent from parts washer 2,060 100 $ 8,500 $ 8,460 1.0

Use an alternate parts washer service, similar to the current

solvent-based service, for which the waste solvent is not

regulated as a hazardous waste. Waste solvent will continue

to be generated, but the generated waste will be nonhazardous and the associated costs to the plant will be reduced. Spent solvent from parts washer 4701 23 1,350 0 Immediate

Install baffles made from waste cardboard in the paint booths

between the painting area and the exit air filters. Much of the

paint overspray will be deposited on the baffles, thereby lessening the load on the filters. Paint booth exhaust filters 590 1 2,560 775 0.3

Used expanded kraft paper exit air filters in place of the fiberglass filters used currently as exit air filters. The recommended filter type has a larger holding capacity than the fiberglass

filters. Paint booth exhaust filters 790 2 2,650 0 Immediate

Replace all conventional air spray paint guns with either highvolume low-pressure or airless-air assisted spray guns. Implementation of this recommendation would reduce paint

purchases, VOC emissions, disposal of paint filters, and

disposal of paint solids. The plant is currently investigating

the purchase of an afterburner to reduce VOC emissions.

This recommendation could eliminate the need for an afterburner or decrease the size of the afterburner required. It is

possible that the spent filters and paint overspray will be reclassified as hazardous waste in the future. In that case,

cost savings will be higher than estimated here. The evaluation presented assumes filters will continue to be disposed

of as nonhazardous waste and that high-volume low-pressure

guns will be installed. This analysis does not include the

avoided purchase of an afterburner. A more detailed tech- Paint solids 675 82 431,600 1,530 Immediate

nological and financial feasibility analysis of this recommen- VOC emissions 22,735 53

dation should be done prior to implementation. Paint booth exhaust filters 35,820 82

Install automatic gun cleaners for cleaning paint spray guns.

Implementation of this recommendation will lead to reduced Solvent waste

solvent purchase and disposal costs. (disposed of with paint waste) 3,000 3 42,500 1,620 0.1

Install a solvent recovery still to recover solvent from the paint

wastes shipped offsite. Reuse the recovered solvent for

paint gun cleaning. Paint waste 62,545 70 12,200 20,660 1.7
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Table 2. (continued)

Annual Waste Reduction

Pollution Prevention Opportunity Waste Stream Reduced Quantity Per Cent Net Annual Implementation Simple

(lb/yr) Savings Cost Payback (yr)

Pack the wood-waste dumpster more efficiently. Carefully

screen the wastes placed in the dumpster to evaluate

whether some of the pallets could be returned to the

supplier for reuse. Wood waste should be stacked in the

dumpster neatly in order to decrease the volume occupied

in the dumpster. Pallets and wood crates —- —- 1,450 0 Immediate

Negotiate with a cement company to accept the plant’s

waste sand for use in cement manufacture. Waste sand —- —- 27,250 4,720 0.2

Sell non-reconditionable drums to a solid waste recycler. Empty drums —- —- 855 0 Immediate

Replace the currently used paint application system with

a dry powder coating system. Implementation of this recommendation will lead to reduced paint/solvent wastes and

reduced VOC emissions. This recommendation could

eliminate the need for an afterburner. The paint booth can

be equipped to capture and recirculate powder that does

not adhere to parts during spraying. This analysis assumes

that the waste filters will continue to be classified as nonhazardous waste and that the powder will be recycled.

The avoided cost of an afterburner is not included in this Paint and solvent wastes 89,350 100 681,000 163,780 0.2

analysis. A more detailed technological and financial Exhaust filters and paint overspray 43,650 100

feasibility analysis of this recommendation should be done Paint solids 825 100

prior to implementation. VOC emissions 43,000 100

Replace the currently used paint application system with supercritical CO2 spraying. In supercritical CO2 spraying, the supercritical fluid replaces as much as 80% of the organic solvents

required for ordinary paint spraying. In addition, the proposed

system offers improved transfer efficiency. This recommendation could eliminate the need for an afterburner or reduce the Exhaust filters and paint overspray 19,600 45 87,230 262,220 3.0

size of the afterburner required. The avoided cost of an after- Paint solids 450 55

burner is not included in this analysis. VOC emissions 34,390 80

1 Net waste reduction
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BULK RATE

POSTAGE & FEES PAID

EPA

PERMIT No. G-35

United States

Environmental Protection Agency

Center for Environmental Research Information

Cincinnati, OH 45268

Official Business

Penalty for Private Use

$300

EPA/600/S-95/008