Clean, Don’t Dump

A little effort to recycle metalworking fluids pays off big

Recycling water-miscible fluids

Recycling water-miscible fluids improves a plant’s profitability and productivity. Photo courtesy of Master Chemical Corp.

Machining is cool. That is if metalworking fluids (MWFs) do the job lubricating and cooling during the process—along with whisking away fines, chips, and swarf.

Today’s fluids have been formulated to last longer than ever before. They come with various additives that offer benefits such as defoaming and rust prevention. They also come with a considerably higher price tag than they did just a few years ago.

In an industry where cost management is key to making a profit, every expenditure needs to be evaluated. A structured fluid management program will need some investment in time and perhaps an initial investment in equipment, but managed properly, it saves. Monitoring, cleaning, and recycling fluids will equate to purchasing less concentrate, increasing the life of coolant in the sumps, increasing the life of tools and sumps, and saving money on disposal.

David Foster, Master Chemical Corp.’s district sales manager for Canada, said, “Many companies lose between 5 and 20 percent of their productivity to mismanagement of their cutting fluids. With a well managed program fashioned around a complete recycling system, they can recycle their fluids virtually indefinitely.

“Some companies have the mistaken impression that fluid recycling is complicated or costly, but it is an easy way to operate more efficiently and affordably. Companies who recycle and manage their fluids can realize a 40 to 60 percent reduction in coolant purchases.”

Begin by Concentrating

Concentration control is key to having MWFs work at their optimum levels. Begin by consistently running at the concentration levels the fluid manufacturer recommends. Then check the concentration frequently using an optical or digital refractometer. Track the desired concentration versus actual concentration on a scheduled basis and correct as needed.

Fluid levels will drop over the course of a shift, day, or week, and operators often add water to increase the volume. This eventually leans the concentration.

Ron Wendt, product manager at Eriez Manufacturing Co., said, “Lean coolant always creates problems. It can cause corrosion, lead to bad tool life, and affect the life of the sump and other machine parts. The best additive for coolant is coolant.”

Evaporation can lead to a richer concentration than desired. “If the fluid concentration runs rich, you can see more instances of dermatitis, residue, and excess usage of the MWF, and it can reduce the fluid’s ability to cool at the point of cut,” said Foster.

A portable tramp oil removal system

A portable tramp oil removal system can be scheduled to travel from machine to machine. Photo courtesy of Master Chemical Corp.

Mix It Up

There is a right way and a wrong way to mix coolant, said Wendt. “Always add the concentrate to the water to get the proper emulsion. If you add the water to the concentrate, you could get a reverse oil-in-water emulsion.” A good rule of thumb, added Foster, is think O-I-L for oil in last. Oil refers to the coolant concentrate.

Hand mixing can work, but it can be time-consuming to achieve the proper concentration. A mechanical mixer can combine coolant with the water to accurately achieve the set levels. After it is mixed, the new or recycled fluid should be stored in a clean tank or put directly into the machine. Concentration and appearance should be checked and adjusted if needed before returning the coolant to the working system.

Remove Tramp Oil

Way lube, hydraulic, gear, or spindle oils make their way into the MWFs and cause their own kind of havoc.

“High tramp oil affects tool life and how much mist gets into the air,” Wendt said. “The oil at the point of cut where the heat is generated tends to get hotter than the water and concentrate mixture and it sprays more of the fluid mix into the air.

“Oil also provides food for bacteria. So the more oil you have, the more food you have. Bacteria levels get very high, it begins to smell, and it can separate. An odor is usually a good indicator of high bacteria levels.”

Tramp oil gets mixed into the coolant by the pumping and splashing actions while the machine is running. It can be removed in several ways if a machine is shut down long enough for free tramp oil to separate from the concentrate. A pump or shop vac can be used to clear away the tramp oil, or a belt, oil wheel, or rope skimmer can make the job easier.

A coalescer will remove the tramp oils from the coolant while the machine continues processing parts. A small amount of coolant from the machine tool sump is pumped into the coalescer’s tank where the tramp oils are separated. De-oiled coolant is returned to the machine. This process has an added benefit of aerating the coolant.

Tramp oils that do not float because the coolant has chemically emulsified them can be removed using a high-speed centrifuge. Wendt said, “As long as the coolant is in good shape, a high-speed centrifuge is the best way to clear the tramp oil, but it is expensive. You have to have the need to do it.”

Unimixer

Mixers can save time and ensure that proper percentages of concentrate are added to water before the coolant is used. Photo courtesy of Master Chemical Corp.

Practice Good Housekeeping

Filtration and a clean machine are important. A shop vac and shovel can be used to remove the chips that have been filtered out and the gunk made up of tramp oil and fines from the bottom of the sump tank. A thorough cleaning job involves pulling the sump out and removing all the waste. As of now, Wendt said, there is nothing that can be added to the coolant to prevent the sludge buildup.

“A sump sucker that pumps out the individual sump and has a filter basket for filtering solids or the conveyor and drag bars that clean a central system can clean the machine faster and take the dirty job off the hands of the operator,” said Foster.

Reduce Disposal

The less MWFs you have to dispose of, the better. Haul-away costs can be very expensive and the fluids must be properly handled by the disposal company or the generator of the waste can be held responsible—even years later. So reducing quantities of spent MWFs by cleaning and recycling also reduces liability.

“It can cost more money to dispose of the fluids than to buy them. And 90 to 95 percent of what will be carried away for disposal is water. Some people try to treat them so they can go down the drain, but this is very difficult to do because they have so many chemicals, biologicals, and metal in them. Evaporation is the only thing that always works. You cook it and reduce the volume, but you still have some waste to get rid of,” Wendt said.

“Biodegradable or not, no matter what it says on the drum, once the fluid has been used, it is not OK to go into the sewer or environment,” said Foster.

Disposal volume with a recycling program, Foster added, can reduce disposal volumes from 50 to 80 percent for most plants depending on four action items:

  1. Begin with stable, bioresistant fluids that can withstand repeated recycling.
  2. Establish and actively supervise a recycling program.
  3. Purchase properly designed and sized recycling equipment.
  4. Control the mechanisms that cause coolants to fail.

“When it comes down to it—it’s really housekeeping,” said Wendt. “Once you put the fluid in, you have to maintain it. It doesn’t take a tremendous amount of time and the rewards are huge. The coolant will last longer, disposal will be reduced, and your equipment will function better.”

www.eriez.com

Electric sump cleaners

Electric sump cleaners can save time by removing chips, sludge, grinding swarf, and other solids. Photo courtesy of Eriez Manufacturing Co.

www.masterchemical.com

Portable air sump cleaners

Portable air sump cleaners from Eriez have single tank capacities from 50 to 1,000 gallons and twin tank capacities from 50/50 to 500/500 gallons. Photo courtesy of Eriez Manufacturing Co.