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Stop dumping coolant and save.

Stop dumping coolant and save

As recently as 10 years ago, recycling was a new and controversial idea in the metalworking industry. Recycling used motor oils, hydraulics fluids, and other petroleum products made economic sense in view of constantly escalating crude-oil prices and the threat of oil shortages. But did it make sense to recycle used metalworking fluids that were mainly water, not oil? It did make sense, and it still does!

The most popular metalworking fluid or coolant is the soluble-oil emulsion--a petroleum oil containing emulsifying agents and used at a low level (usually 5 percent) in water. The small amount of oil provides lubrication; the water provides cooling. Also, the so-called synthetic and semisynthetic metalworking fluids are mainly water.

Ten years ago, a quality metalworking fluid cost about $8/gal by the drum. But when that gallon was diluted with 19 gallons of water in the sump, its cost fell to about $0.40/gal. When it finally became too contaminated for further use, it could be hauled away to a convenient dumpsite for as little as $0.10/gat. With economics like that, there was little incentive for a company to consider recycling its used fluids.

That was ten years ago. Today we can still buy a quality metalworking fluid for $8 to $10/gal, and dilute it 20:1 in the sump. But the days of dime-a-gallong haul-away and disposal costs are gone forever. Public concern over the accumulation of chemical waste has resulted in a barrage of legislation that has profoundly altered the way metalworking companies must handle their contaminated coolants. Used coolants are considered hazardous wastes because they contain sulfides, heavy metals, petroleum hydrocarbons, and sometimes chlorinated solvents. These components make disposal expensive, difficult, and stringently regulated.

Catch 22

Coolant manufacturers increase the sump life of their coolants by adding chemicals to the formulation to overcome the effects of hydraulic oil and machine lubricants, but as a consequence significantly increase the cost of disposal when the coolants finally do break down. To fill a sump with freshly mixed fluid at 5-percent concentration may still cost only $0.40/gal but it could easily cost $4/gal for a hazardous-waste transporter to haul it to a disposal site, pay dump fees, surcharges, taxes--and then more taxes at the end of the year, when it becomes too contaminated for further use.

Theoretically, a quality coolant should last almost indefinitely. In practice, however, contamination soon impairs its effectiveness. There are three major types of contfaminants: Metal chips and fines, tramp oils, and bacteria and fungi. One function of the fluid is to keep the machining surface washed free of chips and metal fines. So it's not surprising that chips and fines begin to build up in the fluid, with a resulting drop in performance.

The most obnoxious and obvious contaminants are microorganisms with colorful names like pseudomonas and desulfovibrio. They can flourish in a metalworking sump and cause odors that can drive the machinists away from their machines. But bacteria and fungi can cause far worse conditions. They can produce sediment and slime, generate corrosive acids, destroy essential fluid components, and actually break soluble-oil emulsions. In the past, when a used coolant was hauled away, it was usually disposed of because of rancidity--bacteria and fungi.

Unplanned obsolescence

Various in-line filters, settling tanks and clarifiers, tramp-oil skimmers, and liberal doses of biocide have long been used to prolong coolant life. But today, more sophisticated methods are required to recycle contaminated coolant.

Eventually, packaged recycling units began to appear on the market incorporating settling tanks, filters and hydrocyclones for solids removal; centrifuges for separating tramp oil from coolant; and pasteurizers or biocide-addition devices to destroy microorganisms. Plants began to purchase and install these units and soon found themselves in the recycling business.

Some companies with fixed installations were happy with the results; others were not. Many factors dictated whether a recycling installation was successful. The technology for the recycling of metalworking fluids had only a few years to evolve, and some equipment became obsolete quickly--soon after purchase. One packaged unit, for example, incorporated a centrifuge that was too slow to provide good separation when large amounts of tramp oil were present in the coolant. New units solved this problem.

Sometimes differences of opinion among vendors of recycling equipment were reflected in design differences in their units, which affected their success in the field. One vendor, for example, insisted that pasteurization was of no value and could even be detrimental in the control of microorganisms. As a result, his system used no fluid heaters in its recycling operation.

Wheels for recyclers

Mobile recycling--the use of portable recycling equipment transported from place to place by a company in business to provide recycling services--evolved from fixed-unit recycling. One enterprising vendor of recycling equipment in Southern California conceived the idea of mounting a centrifuge and auxiliary equipment on a truck and mobilizing it into a customer's place of business to recycle contaminated fluid while waiting for permanent equipment to be delivered and installed.

The situation soon grew into a technical illustration of the old proverb about the tail beginning to wag the dog. Mobile-recycling technology evolved rapidly to the degree that this company, Fluid Recycling Service, was eventually able to patent the process and recycle not only water-based coolants but cutting oils, hydraulic fluids, and some EDM fluids. It also became apparent that the mobile recycling service offered flexibility to the metalworking industry that fixed recycling installations could not.

In the case of an airframe manufacturer, management discontinued the use of its own recycling equipment and brought in Fluid Recycling Service. The company was gratified to find that most of its recycling problems disappeared. The disposal problems of hazardous-waste coolants were practically eliminated. Machinists were happy with the quality and performance of the recycled coolant. Expenditures for make up cooland also decreased.

Another aerospace firm attempted its own recycling without pasteurization, but found it impossible to control bacteria. Operators had to dispose of thousands of gallons of rancid coolant at a cost as high at $4/gal. The fluid-recycling process, which included pasteurization and stabilizers, eliminated the need for disposal of spent coolant. The only disposals now are of machine cleaner, used when machines are down.

The quality of the recycled coolant is considered excellent and equivalent to new. Recycling is carried out on batches of 1000 gal every five weeks.

How it works

Usually the service company conducts a preliminary survey of the prospective customer's machining operations, taking samples of contaminated coolant to determine its suitability for recycling.

Two holding tanks, one for contaminated fluid and one for recycled fluid, are then provided, sometimes by the customer but more usually by the service. Every few weeks, the service brings in its equipment, plugs into the plant's power supply, and recycles whatever contaminated fluids have been collected since the last visit. Usually the concentration of the recycled fluid must be adjusted by the addition of fresh concentrated coolant from the drum, or by water; and often biocide is added as well to protect the pasteurized recycle against re-infection by microorganisms remaining in machine sumps and lines. Recycling firms often offer supplemental services such as sump cleaning and changing. Tramp oils and metal fines separated in the course of recycling are set aside to be given or sold to oil and scrap-metal reclaimers. No costly disposal of hazardous wastes is necessary.

For information on fluid recycling in your area, contact Fluid Recycling Service Inc, 1717 Newport Circle, Santa Ana, CA 92705-5196. Phone 714-754-7220.
COPYRIGHT 1989 Nelson Publishing
No portion of this article can be reproduced without the express written permission from the copyright holder.
Copyright 1989 Gale, Cengage Learning. All rights reserved.

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Title Annotation:mobile recycling service
Publication:Tooling & Production
Date:Mar 1, 1989
Previous Article:Machine-tool VRAs: too little too late?
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