Tech Talk
When seeking an "environmentally friendly coolant filtration system", what is available on the marketplace?
For the last decade or more, manufacturers have made dramatic improvements in quality, cost and delivery in order to successfully compete. Now, going into the next century, there’s a new “competitiveness” issue to deal with — environmental compliance.
Evidence of the dramatic impact that tough new environmental mandates and sky rocketing waste disposal costs will have on manufacturers is becoming increasingly apparent. Already U.S. firms are said to be spending $140 billion annually on compliance costs, and the number is rising at 9% a year. Companies like Ford Motor Co., seeking to “stay ahead of the curve,” have established an objective that, by around the year 2000, no scrap or waste, including coolant and grinding sludge, will leave Ford; everything will be recycled and nothing will go to the land fills. Progressive companies in the metalworking industries are bound to follow suit.
A system called SIERRA. Before companies can effectively meet this environmental challenge new technology must be developed. One company at the forefront of this effort is Rockford, IL based BARNES INTERNATIONAL, INC. and its Filtration Systems Division. Barnes is the leading manufacturer of the coolant filters that separate used coolant from chips and swarf, and recirculate it back to the machines for reuse. Chips and swarf (sludge) are then disposed of. Until recently, not much thought was given to the disposal of this waste material, let alone the “filtration aids” and disposable filter media used in the traditional filtration processes. This extra waste material was simply hauled off to landfills and dumped at very little additional cost to the manufacturer. Now, all that’s changed, according to Barnes Vice President Terry Connell. “In recent years we’ve seen increasing customer requests for coolant filtration systems that use permanent media, don’t require filter aids, and discharge dry swarf,” says Mr. Connell. “The reason is that waste haulers are today charging manufacturers a heavy premium for hauling the sludge, the media and the filter aid — all of which are still saturated with coolant. Our customers need a way to get ultra-clean coolant delivered to their machines, while at the same time discharging swarf in a dry condition — and without the use of hazardous filter aids and disposable media. Today, we are able to offer them the only filtration system available in the world that delivers all of these capabilities.”
Barnes found the solution in Europe, where coolant disposal and recycling are said to be fully 16% of the total cost in a machining operation (cutting tools, for instance, are only around 4%). A transfer line user in Germany might spend on coolant disposal up to five times the original coolant cost. It’s no wonder, then, that in Europe the need for better coolant filtration is particularly acute — and why a breakthrough technology already existed there that Barnes was ultimately able to license and begin manufacturing here, as the Kleenall SIERRATM Permanent Media Filter. “A leading Italian filtration company already had this filter technology at work at Fiat, and it’s the only filter of its kind at the new Audi facility in Hungary,” says Mr. Connell. “When we found out what it was capable of doing, and saw it in action, we entered into a licensing agreement with the Italian firm to build them here at Barnes as the SIERRA.”
It’s not surprising Barnes and Mr. Connell were excited about the prospects for the technology in the U.S. The Kleenall SIERRA employs new patented technology to do what apparently no other filtration system has succeeded in doing: deliver ultra-clean coolant and very dry swarf — but without the need for costly disposable filter media or filter aids. Consider, then, these potential user benefits:
- Swarf is discharged dry, so it’s directly re-cycled or disposed of in compliance with EPA requirements. The added cost of processing and disposal of coolant-laden swarf is largely eliminated.
- The high costs for removal, replacement and disposal of replaceable fabric filtration media is eliminated too, because Kleenall SIERRA uses a permanent media vacuum design that’s self-cleaning and doesn’t require regular replacement.
- Coolant is automatically filtered down to an average 7-10 microns, so it lasts much longer and greatly reduces both disposal and replenishment costs.
- Tool life increases, and grinding wheels require fewer dressings, because abrasive waste particles are removed from the recirculating coolant before they can do damage.
- The quality of surface finishes improves, with less potential for rejects and scrap.
Cost savings are significant. Mr. Connell gives one example of a company that disposes of eight 55-gallon drums of wet sludge a week and pays several hundred dollars per drum for a waste hauler to dispose of it. However, if the sludge could be dried in advance, the company could actually sell each drum, saving the company over US$100,000 a year.
There are other cost issues to consider as well. Conventional filters for grinding and honing operations sometimes use filter aids like alpha cellulose or diatomaceous earth that help in the filtration process. In fact, good filtration in cast-iron applications is all but impossible without their use. But diatomaceous earth is considered a hazardous substance, making the sludge all the more difficult and expensive to dispose of. And the alternative, alpha cellulose, is often costly to use as well as dispose of.
Still other problems exist. The disposable fabric filter media that’s normally used is often no longer acceptable because of the cost of disposing of it as a hazardous material. And then there’s the additional cost to consider of replenishing the coolant disposed of with the sludge.
Wide range of applications. The Kleenall SIERRA can be applied to almost any abrasives finishing operation, and even EDM and parts washing. The standard system has a capacity of up to 300 GPM, but the technology has been used in central systems of up to several thousand GPM in capacity.
“Just as in Europe, manufacturers here will undoubtedly have to take steps to address environmental compliance and disposal costs,” concludes Mr. Connell.
The availability of the Kleenall SIERRA finally addresses long-standing coolant filtration issues — and offers users the filtration technology they’ll need entering the next century.
An “inside look” at this self-cleaning, permanent-media vacuum design:
Here’s an inside look at how the Kleenall SIERRA’s patented process works:
- Dirty coolant from the machining operation flows into the collection tank
- Spanning the bottom of the tank is a drag-out chain that rests on top of a permanent-media belt
- Both rest on a wedge-wire stainless steel grate that forms the top of a vacuum chamber
- The pressure differential between the collection tank and the vacuum chamber pulls the coolant through the permanent-media belt and wedge-wire grate into the vacuum chamber, where it is pumped to the clean coolant tank for recirculation.
- Particles as small as 7 microns are trapped by the permanent-media belt before they can enter the vacuum chamber — only ultra-clean coolant is returned to the machining operation.
- As swarf builds up on the permanent-media belt, the pressure differential increases between the collection tank and the vacuum chamber. A vacuum switch detects this and, at a predetermined level, starts the index cycle (a timer can also be used to initiate the cycle). The drag-out chain advances at a set distance, pulling the permanent media belt with it. The filtering cycle then begins again, using a clean section of the permanent-media belt. The entire process is automatic.
- During the index cycle, swarf is discharged automatically up the ramp. A vacuum drying chamber is used to remove liquid from the swarf. The swarf is then discharged in a dry or near-dry state.
- The permanent-media belt undergoes a 3-stage process of cleaning before it is returned to the collection tank for use in the filtering cycle. First, counter-current air-blowing from the underside of the belt helps dislodge particles. Then a patented roller device called a ROTOVAC rotates at a very high speed to create a vacuum effect across the width of the permanent-media belt, removing the remaining particles. As a final step, the belt is washed with a clean coolant by a series of nozzles before re-entering the collection tank.
