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Extending equipment life.

Manufacturers of plastic parts are extending the life of their hydraulic fluid, servovalves, and pumps by means of the hydraulic system inspection program devised by Mobil Oil Corp. (Fairfax, Va.), combined with their DTE 20 series of stabilized antiwear hydraulic fluids. Facilities that use the program and DTE fluids include the GTE Products Corp. automotive and miniature lighting plant in Seymour, Ind., and Southern Case Inc. in Raleigh, N.C.

This program addresses a problem common to hydraulic systems in plastic processing: overheating of the lubricant as it passes through high-pressure pumps and valves. This was the experience of Southern Case, a manufacturer of blow-molded plastic products, primarily rigid high-density polyethylene carrying cases for hand tools, cameras, camcorders, and guns. These machines cycle constantly as they mold each piece and were plagued by leaks.

Temperatures up to 215 [degrees] F in Southern Case's hydraulic systems broke down the hydraulic fluids, lowered their viscosity, and shrunk and hardened the O-rings and seals in the hydraulic systems, causing leaks. In addition, the higher oxidation caused by the excessive temperatures created a buildup of by-products in the servo-valves that caused them to malfunction and eventually destroyed the valves.

Mobil Oil inspectors discovered that the hydraulic fluid cooling towers at the Raleigh plant were only operating at between 50 and 60 percent efficiency due to scale buildup. Southern Case technicians refurbished the towers and hydraulic fluid temperatures dropped to the 110 [degrees] to 140 [degrees] F range.

Southern Case operators also began using Mobil's DTE 24, 25, and 26 hydraulic fluids in the blow-molding machines. These antiwear fluids are formulated to disperse oxidation by-products so that they will not collect on critical parts of a hydraulic system. The fluids are also formulated not to corrode pump metals or contaminate the fluid with particles, to provide an extra measure of rust protection, and to tolerate small amounts of water while causing larger amounts to drop out.

Every six months, Southern Case and Mobil technicians sample the fluids at the Raleigh plant for viscosity, water, sediment, dirt, and metal particles. The fluid is replaced if it is found unsatisfactory.

Southern Case reported that since working with Mobil Oil, hydraulic fluid usage at its Raleigh facility dropped from 14,000 gallons per year to less than 4000 gallons per year, primarily due to stopping leaks. Change-outs of hydraulic fluid are now necessary every two years, rather than every six months, as was the case previously.

There are also fewer servovalve and pump failures at the plant. Servovalve repairs dropped from twice a month to twice a year. Pump failures declined from three a week to about one a month. Southern Case calculated that Mobil's hydraulic program and DTE fluids saved the company more than $65,000 in its first year of operation.

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Title Annotation:Mobil Oil Corp. hydraulic fluids save Southern Case Co. on maintenance and repair costs
Publication:Mechanical Engineering-CIME
Date:Jul 1, 1993
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