A Separator Solves The Tramp Oil Problem

With their strong attention to routine housekeeping, it's not surprising that this shop carefully researched all methods for removing tramp oil from coolant in machine sumps. If tramp oil is allowed to build up in the coolant, the resulting shop odor, smoke generation and unpleasant conditions for the operators will quickly undermine all efforts to keep a clean shop and maintain an optimum working environment.


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A visitor’s first impression when entering High Tech Machinists, Inc. (Chelmsford, Massachusetts) is that it is an exceptionally clean shop. This is not by chance. According to John Bissonnette, operations manager for High Tech, “Maintaining a clean shop and a good work environment is an essential element in our company program to be a leader in precision machining of complex parts for the communications industry.” Obviously, High Tech is achieving its objective, having grown in 16 years from a one-machine shop to a company with 42 machines and further expansion on the way. When the company planned to move from its original overcrowded building to the present custom-built facility 2 years ago, managers reasoned that to maintain High Tech’s position as a high quality, reliable shop, they had to provide a clean and safe working environment for the skilled machinists. In the new building, the machines are positioned with ample clearance for access to all sides. The air quality is maintained with numerous suspended circulating air cleaners. Even the floors are washed daily.

With this level of attention to routine housekeeping, it is not surprising that High Tech also carefully researched all methods for continuously removing tramp oil from coolant in the machine sumps. If tramp oil is allowed to build up in the coolant, the resulting shop odor, smoke generation and unpleasant conditions for the operators will quickly undermine all efforts to keep a clean shop and maintain an optimum working environment. In addition to the detrimental effect on shop conditions, tramp oil in the sumps causes excessive tool wear and reduces machine operating efficiency. Since about 70 percent of High Tech’s production is in aluminum, careful attention must be paid to the selection of devices to remove tramp oil from the sumps, because aluminum chips floating in the tramp oil on the surface of the sumps causes severe operating problems with many pump/separator units.

After evaluating a number of tramp oil removal devices, Mr. Bissonnette selected the Model #355 filter/oil separator supplied by Keller Products, Inc. (Lexington, Massachusetts). The features of the Model #355 that are particularly important for High Tech’s requirements are a high capacity bag filter to remove floating chips before they enter the separator system, a 2 gallon per minute air-operated diaphragm pump that is essentially maintenance-free because it is protected by the bag filter, permanent oil separation elements that never need cleaning, and the easy portability of the compact 18-inch by 30-inch unit.

The cart-mounted Model #355 can be set up at a sump simply by connecting a ¼ inch compressed air line with no electricals. With a coolant recirculation rate of 120 gallons per hour, the separator can clean a typical 60- to 100-gallon sump in about 3 hours, and then it can easily be moved and set up at another sump. One Model #355 can effectively maintain the coolant in the sumps of ten machines by cleaning each sump once per week. High Tech uses two of the separators to treat the sumps of about 20 CNC machines. Mr. Bissonnette reports that as a result of the regular sump cleaning program with the separators he is readily able to maintain the clean shop environment, and in addition, he finds that tool wear is significantly reduced because the coolant is free of tramp oil.

Another coolant-related issue that Mr. Bissonnette wished to address when High Tech moved to its new building was the large volume of coolant lost with the disposal of wet chips. His objective was to approach 100 percent recycling of coolant as closely as possible in order to reduce the cost of coolant disposal and the corresponding purchase of makeup coolant and also to practice High Tech’s philosophy of environmental good citizenship. He installed a chip pelletizing machine, which succeeded in squeezing virtually all the coolant from the chips. However, the coolant recovered from the chip pelletizer contains fine aluminum particles plus tramp oil, both of which must be removed before the recovered coolant can be recycled to the coolant makeup system. Mr. Bissonnette solved the problem of treating the recovered coolant by installing a stationary filter and oil separator system supplied by Keller. The coolant recovered in the pelletizer drains into a collection sump where some of the entrained tramp oil is removed. The coolant is then pumped through a bag filter, which removes particles down to 25 microns, and then into a holding tank. A Model #355 recirculates the coolant in this tank to remove any remaining tramp oil and solids. The treated coolant is transferred to the fresh coolant makeup tank where it is mixed with fresh coolant and supplied as makeup to the machines.

The coolant recovery and recycling system now works perfectly. High Tech’s coolant loss is now less than one drum per month, compared to six drums per month before installation of the pelletizing and recycling system. With his careful attention to tramp oil removal and coolant recycling, Mr. Bissonnette has been able to implement High Tech’s objectives of providing exceptionally clean working conditions and being an environmental good citizen, while at the same time saving a substantial amount of money in coolant and tooling through efficient machine operation.

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