January 2012 / Volume 64 / Issue 1|
Waste not, spend not
By Alan Richter, Editor
Courtesy of Eriez Recycling coolant pays big dividends for job shops.
When machine shops start recycling, one material often leads to another. For example, many discover coolant recycling after they establish a chip recycling program. Once they do, shops find out that coolant recycling not only makes economic sense, but can improve part quality, extend tool life and help maintain a cleaner working environment. Shops also have a choice between investing in recycling equipment and having a service provider do the job.
PNM Co. is an example of a shop that began recycling on the chip side. About a decade ago, the Fresno, Calif., job shop began briquetting chips, targeting aluminum ones because more than 90 percent of its work involves machining that material, noted Dave Counts, company president. He added that the briquetting machine eliminated several hours of labor each day from loading and transporting two to three chip bins, but the shop then needed to deal with the coolant squeezed from the chips.
“We were holding onto the coolant and skimming some oil off of it and having a lot of it trucked away,” Counts said. “It was very time-consuming. The cost was way up there to do all that stuff.”
PNM conducted an online search to find a coolant recycling system that suited its price and performance requirements and located the SmartSkim centralized system from Universal Separators Inc. After installation, the shop saw its coolant consumption drop by a third and an even larger reduction in its cost to have used oils hauled away. That’s because, with the coolant and contaminants removed from the way and hydraulic oils, the recycling company charges less per gallon to remove it. “We fill up a 55-gal. drum every 3 or 4 months. Before, we were filling four or five drums a month,” Counts said, adding that payback was less than a year.
PNM purchased the coolant recycler when it had 15 CNC machines. The 50-worker shop now has 20 CNC machines and the system still has remaining capacity, according to Counts. Most of those machines have oil skimmers to enhance coolant cleanliness.Cutting Costs
PNM is not alone in its motivation to purchase coolant recycling equipment. Bill Gimbel, vice president of sales and an owner of Universal Separators, Verona, Wis., noted that many shops consider coolant removal bills a cost of doing business and only after they obtain a device to extract coolant from chips do they realize the benefits of coolant recycling. “We get a lot of leads that way,” Gimbel said. “They might save the coolant but if they’re not reusing it, they’re paying to get rid of it.”
Although coolant isn’t cheap and prices continue to rise, the larger expense is paying to have dirty coolant hauled off-site, according to Mark Kluis, general manager for Universal Separators. “Customers tell us that’s the bigger savings.”
Courtesy of Sanborn Technologies
Others, however, say recovered coolant represents the biggest savings. According to Steve Friedman, president of coolant recycling system manufacturer Sanborn Technologies, Walpole, Mass., the rule-of-thumb cost analysis of a coolant recovery system includes the cost of buying new coolant at $1.00 per gal. ($20 per gal. of concentrate diluted to a 20:1 ratio) and the cost of disposing of used coolant at $0.50 per gal. Therefore, every gallon of recovered coolant saves a facility $1.50. “Over the years, many localities have found the cost of coolant disposal has remained somewhat constant as treatment technologies have improved for waste haulers and treaters, but the costs for coolant concentrate have risen dramatically as the cost of base stock has increased,” he said.
Friedman noted that many coolant recycling systems somewhat extend the life of coolant but only an integrated coolant recovery system will return like-new fluid of the highest quality back to the machine tools.Recycling Equipment
The role of coolant recycling equipment is to remove the tramp oil, particulates and bacteria, returning the coolant to like-new condition and enabling it to have a long life. The tramp oil resides in the rag, or cream, layer at the top of the coolant. “The rag layer kills the useful life of the coolant, creates bacteria, causes dermatitis and ruins tool life,” said Tim Hanna, managing director of PRAB Fluid Filtration Div., Kalamazoo, Mich., a manufacturer of fluid filtration equipment. He added that minimizing tramp oil in a machine sump reportedly extends tool life by at least 15 to 20 percent. “I’ve heard of as much as doubling the life of tooling.”
Courtesy of Universal Separators
In addition to a bag filter that removes suspended solids, Hanna explained that the company’s Guardian coolant recycling system has a barrel skimmer that sits below the coolant surface and a double-diaphragm air pump that pulls the coolant and rag layer into the tramp oil separator. In the separator’s first chamber, the layer of tramp oil rises to the top and is extracted through a weir.
The coolant then travels through a baffle into the second compartment, or media section, where coalescing occurs, turning small droplets of tramp oil into larger droplets. That’s achieved by flowing the coolant through plastic tellerettes and pall rings, which grab the small droplets and form larger ones. The droplets then rise to the top of the surface with the assistance of an air sparger and are extracted through a second weir. The separator keeps removing contaminants as gravity overflows coolant from the clean side of the system to its dirty side in a continuous processing cycle before the clean coolant is fed back to the machine sump.
“If you’re doing a 200-gal. sump, it’s fair to say in 3 to 4 hours you remove 98 percent of all tramp oils,” Hanna said. The company’s standard systems process up to 1,500 gal. per hour.
He noted that system options include an ozone generator to kill bacteria, a polishing filter for particle filtration down to 5µm and hose reels. For example, while an installation might feature a fully automatic, closed-loop, central recycling system, such as one used by NASA, other customers use hose reels to top off sumps or recharge coolant after cleaning. “The hose reels are filled with clean coolant and, as a sump is evacuated, they just pull the handle, like when filling a car’s gas tank, to fill up the coolant sump,” Hanna said.
Courtesy of Sanborn Technologies
The recycling system reduces new fluid purchase costs by 45 to 75 percent and reduces hazardous waste disposal costs by 50 to 90 percent, according to PRAB. Nonetheless, the removed tramp oil must be hauled away because various oils, such as way lubrication, hydraulic and mold release oils, are mixed together and can’t be effectively separated. However, tramp oil becomes an energy source, such as for a heater that burns used oil, and suitable for sale to oil reclaimers, according to Barry Nehls, general manager of Eriez Hydroflow, Erie, Pa., a manufacturer of fluid recycling and filtration equipment.Coolant Consistency
When using recycled coolant from a central system involving multiple machines producing the same component, Nehls emphasized that it’s critical that the fluid delivered to each machine is at the same pressure, level of cleanliness, concentration and temperature to achieve application consistency.
That’s the case at one manufacturer that applies water-soluble coolant to creep-feed grind Inconel parts for power transmission turbine engines, where maintaining a constant temperature is particularly critical, he noted. The coolant is filtered to remove particles down to 5µm, and the system includes an optional coalescer to continuously remove tramp oil. “They keep the fluid in as good shape as it can be kept,” he said.
Nehls added that it’s also important to establish and adhere to a coolant recycling schedule, with higher-quality coolant lasting longer. “If you wait until you have odors, you’ve waited too long,” he said, noting shops will then start experiencing surface finish problems and significantly shorter tool life.
Another problem with having too long of a coolant recycling interval is microbiological infestation. That can become particularly prevalent when a sump is down for an extended time, allowing tramp oil to seal the sump surface, Nehls explained.
Courtesy of PRAB
Before adding fresh or recovered coolant to the mix, equipment must be thoroughly cleaned with a bactericide to remove any biological growth, such as fungus, which can hang under a machine like Spanish moss. “If you dump clean coolant back in and the microbial activity hasn’t gone away, you just gave it fresh food,” Nehls said. “You just rang the dinner bell.”
He pointed out that two types of bacteria grow in metalcutting fluids: aerobic and anaerobic. Aerobic bacteria need oxygen to live and although they will deplete a fluid of its oxygen and eventually break it down, the process isn’t as quick as the work of anaerobic bacteria. “They’re not that serious,” he said about aerobic bacteria.
Anaerobic bacteria, however, break down coolant emulsifiers, which hold the water and oil together. The byproducts of that are two-carbon acid and usually sulfur dioxide, known by its rotten egg odor. “Once that happens your emulsion is in serious trouble,” Nehls said. “If the coolant goes into a high-speed centrifuge, it’ll usually tear the emulsion apart.”
Although the vast majority of new coolants are suitable for recycling in a high-speed centrifuge, which rotates at about 9,800 rpm, there are products in which the emulsifying package is not strong enough, and some of the concentrate is stripped out during centrifugation, according to Miles Arnold, vice president for Coolant Management Services, Los Alamitos, Calif.Mobile Recycling
Once they’ve decided to recycle coolant, shops needs to decide between purchasing equipment or using a service provider. For shops using the latter option, Coolant Management Services provides coolant recycling services at the customer’s facility. CMS, which services Southern California, travels to the machine shop, evacuates coolant from machine sumps, brings it to its truck, runs it through a centrifuge to remove particles to 5µm and up to 99.5 percent of the tramp oil and brings the filtered product back to the machines.
Arnold explained that the company is a full-line distributor that also sells coolant recycling equipment, but it’s frequently less expensive for shops to use a service. CMS also helps companies manage their coolant and can provide an on-site laboratory for coolant testing.
“Our burden rate [indirect costs associated with employees, over and above gross compensation or payroll costs] is considerably less than the rate for most customers,” Arnold said. He noted that a shop needs to use a total of about 700 gal. of coolant in their machines to make the service feasible, and most customers have their coolant recycled every 6 to 8 weeks.
Another service CMS provides is machine tool cleaning, which complements coolant recycling, Arnold added.
Many shops don’t effectively clean their machines, according to Bill Shaver, owner of Fluid Management Inc., a coolant recycling and machine cleaning service with locations in Minneapolis and Greenville, S.C. “That’s one of the reasons they use more coolant than they should,” he said. “They leave the particulate and bacteria in the machine and then the clean coolant is inoculated with bacteria and fungus right away.”
Even when shops do thoroughly clean equipment, it requires operators taking time away from production or maintenance personnel with multiple demands. “What’s more important, cleaning out a tank or repairing a machine that has electrical faults and is nonproductive?” Shaver asked rhetorically. For customers that don’t run 24/7, Fluid Management performs recycles and cleans during off-hours, he noted.
Shaver added that cleaning a machine involves removing the swarf and scrubbing the sump tanks, pumps, screens and conveyors—“anything that has contact with the coolant.” After cleaning, the machines are thoroughly dried with clean shop towels so no soap residue remains.
Courtesy of Eriez
Regardless of who performs the recycling, recovered coolant lasts virtually forever. Shaver pointed out that of Fluid Management’s seven original customers from when it started in 1993, five out of the remaining six have not disposed of their coolant and the one that did needed a different coolant because the shop’s product mix changed. After checking coolant concentration at the start of each shift, Shaver recommends adding coolant at the correct mixture level to maintain the proper concentration level in the sump.
And a high level of recycling, obviously, significantly reduces coolant consumption. For example, Shaver noted that one customer in South Carolina was dumping 150,000 gal. of coolant annually prior to beginning recycling. “When we finished our first year, they dumped zero gallons of coolant and reduced their coolant purchases from about 26 totes a year to nine,” he said.
While setting up a coolant recycling program requires an investment, it typically pays for itself in a matter of months or at most a year. If investing in a system is not an option, using a service can achieve the goal with less upfront cost. In either case, any shop that is not recycling its coolant may be seeing some of its profits—as well as most of its coolant—going right down the drain. CTEAbout the Author: Alan Richter is editor of CTE, having joined the publication in 2000. Contact him at (847) 714-0175 or firstname.lastname@example.org.
Recovering a 'precious' metal
Coolant Management Services
Fluid Management Inc.
Nowak Machined Products
PRAB Fluid Filtration Div.
Transor Filter USA
Universal Separators Inc.
Shop saves big through waste minimization
understands the financial drain of paying to have tramp oil-saturated coolant hauled away. Haulage actually costs more than replacing the shop’s semisynthetic coolant, according to Mike Orchard, maintenance coordinator for Muskegon, Mich.-based Nowak. The company produces aluminum, gray iron and steel parts, primarily for motorcycles.
When tramp oil, such hydraulic oil from spills and machine oils used on the parts, caused the coolant to lose some lubricity and when the sight and smell of a machine sump became too offensive because of bacteria and fungus growth, the company disposed of the fluid. “We had no way to clean that coolant,” Orchard said, “so we just put it in a big container and had someone from a waste hauling company come and pick it up.”
The shop, which has about 50 machine tools with 20- to 300-gal. coolant sumps, tried removing tramp oil with belt skimmers, but found they weren’t effective when machines were running. While searching for a solution, Nowak found PRAB, Kalamazoo, Mich., which installed a centralized coolant recycling system for the parts manufacturer to use on a 2-month trial basis.
Because the system effectively recovered the contaminated coolant, Nowak purchased a coolant recycler that holds up to 400 gal. of clean coolant and 400 gal. of dirty coolant based on PRAB’s sizing recommendation. That was about 2½ years ago, and the equipment has required little maintenance other than routine cleaning and filter changes since then, according to Orchard. “We replaced the seals on the pump once, but it wasn’t a major issue,” he said. “The system runs around-the-clock except when we’re not here on the weekends.”
In addition to coolant from the sumps being recycled, Nowak also recycles the coolant the shop drains from chips before selling them.
Since installing the coolant recycling system, Orchard noted that the waste hauler infrequently visits to remove the collected tramp oil.
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