MANUFACTURE OF FABRICATED METAL PRODUCTS # 58

This facility manufactures nails, staples, and the tools to drive these fasteners. The fastening tools are made of aluminum, magnesium and carbon steel. To produce these fastening parts, grinding, milling, drilling, lathe working, heat treatment and metal finishing operations are employed. Prior to many of these operations, parts are cleaned in a cold application using 1,1,1-trichloroethane (TCA). Approximately 6500 gallons per year of TCA were used in the operations. Waste TCA was being discharged as effluent at levels twice as high as the allowable limit. Absorbents used around the machine tools also showed levels of TCA that prevented disposal in the regular trash. The company decided to attempt to eliminate the use of TCA from the manufacturing of fastening tools.

A task force identified for potential causes for excessive TCA cleaning wastes:

Process modification

The clean technology involved initially reducing 1,1,1-trichloroethane use and finally eliminating its use by installing aqueous cleaning systems.

Initially, the firm reduced the number of cleaning stations from 37 to 27. Costs associated with dumping of cleaners were the responsibility of each department. Operators were surveyed to identify TCA use and determine opinions for alternatives.

The selected pollution prevention measure was to use a heated tank with liquid agitation, provided the necessary chip removal and oil removal systems were present.

In the machine maintenance areas, two mineral spirit cleaners were installed and the company is in the process of installing aqueous-based cleaning systems. At the time of this case study, they had installed 13 aqueous washing systems and 2 mineral spirits cleaning systems. They expect to have a total of 15 aqueous systems, which are centralised within departments, which will replace 37 former TCA locations.

Other processes implemented in addition to the processes for reducing TCA included treating soapy water by oil separation, and in-house pH neutralization. Also, a precision grinder was replaced by an older piece of grinding equipment, which does not require virgin material.

There are regulatory advantages that cannot be directly quantified. Permit concerns associated with TCA discharge were greatly diminished by successfully negotiating with the regulatory agencies to tie the metal finish discharge into the nearby town sewer system. The company will no longer have to report under SARA for TCA, which will save considerable time.

Eliminating TCA will also allow the company to present a strong example to the State and local communities that they are doing their part to decrease overall emissions, thus increasing community relations. Finally TCA air discharges will be eliminated. This may be especially important since TCA has come under intense scrutiny and regulation because of its ozone depletion and air toxics potential.

Quantities of waste generated and feedstock used, before and after the implementation of cleaner production measures are tabulated below.

The anticipated capital expenditures during 1990-1991 on this project are $80,000. This includes costs for aqueous cleaning systems, wastewater collection equipment, and equipment installation.

Operational and maintenance costs of $15,000 are required for heating and pumping aqueous fluids.

With approximate annual savings of $56,500 and $80,000 in capital costs, the pay back period is approximately 1.4 years.

A net savings of $7,000 is expected from reduced disposal costs, since the disposal costs in 1988 were $9,000 and they expect that the cost for disposal of separated oils will be $2,000. In addition, the annual cost saving associated with the disposal of absorbents no longer contaminated with TCA is $34,000.

A net saving from replacing virgin TCA and aqueous cleaners will be $7,000. This was calculated from the difference in the 1988 cost of virgin TCA ($27,000) and the 1991 costs for aqueous cleaning solution ($20,000).

Other processes implemented, in addition to the processes for reducing TCA, included treating soapy water by oil separation and in-house pH neutralization. The annual savings from segregation and in-house treatment are $20,000. The savings from changing to an older grinder lead to annual savings of $1,200 from reuse of the coolant. The annual savings from preventing spoilage of coolants are $1,300.

Overall, the potential saving from eliminating TCA is approximately $56,500 per year (including the extra utility costs presented below in 8.0).

There is an extra electrical cost associated with heating and pumping aqueous cleaning fluids equal to $15,000 per year. TCA cold cleaning had no utility cost.

Type of Source Material: EPA Conference Proceedings

Citation: American Electroplaters and Surface Finishers Society, Inc., and the Environmental Protection Agency; "12th AESF/EPA Conference on Environmental Control for the Surface Finishing Industry"; January, 1991; pp. 165-181.

 

Level of Detail of the Source Material : Additional information is provided on the identification of the problem and task force that decided on the solutions.

 

Industry/Program Contact and Address:

Kevin P. Vidmar, Div. Manager, Environmental Affairs,

Stanley Fastening Systems, Route 2, East Greenwich, RI 02818

United States.

This case study was originally abstracted form the document cited above for the US EPA's Pollution Prevention Information Clearinghouse. In 1994 it underwent a UNEP IE funded review for quality and completeness. It was edited for the ICPIC diskette in August 1995.

Subsequently the case study has undergone another technical review by Dr Prasad Modak at Environmental Management Centre, Mumbai, India, in September 1998.