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COVER PAGE |
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IBT |
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ISG |
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IMT |
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MATERIAL HANDLING |
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PT |
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FLUID POWER |
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GENERAL INDUSTRIAL |
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IBT MEDIA |
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LEAN SIX SIGMA |
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ELECTRICAL |
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RUBBER |
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TRAINING |
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SAFETY |
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TECH X 500 |
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Dow's Molykote® To The Rescue
Oil and other lubricants have additives. Sometimes, the side effects of those additives can be harmful to the very equipment the lubricant was supposed to protect. In one case, anti-oxidant additives in a conventional oil reacted to process gases, causing corrosion and pitting inside the pump casing. The result was catastrophic failure every four to six weeks.
Dow Corning had installed a new two-stage vacuum pump in one of the processing plants in its chemical manufacturing complex in Midland, MI, where the pump was needed to draw gases from a process reactor vessel. The pump was put into operation using a conventional mineral oil that was specified by the original equipment manufacturer (OEM). During the first nine months of operation there was a catastrophic failure every four to six weeks.
The pump drew hydrochloric acid vapors from a reactor vessel used to manufacture pharmaceutical “actives.” During the vacuum process, some of the acidic vapor condensed into a liquid form and mixed with oil inside the chamber. As the oil stream hit the inside of the chamber casing, the zinc-based anti-wear additives in the conventional oil mixed with the hydrochloric vapors and catalyzed a reaction that drew metal from the casing and created ferric chloride. The result was a “pitting” action in which metal particles flaked off of the inside casing of the vacuum chamber, where the tips of the rotor vanes have to provide an oil and vacuum seal. Cracks in the chamber housing revealed further deterioration.
The pitting created imperfections that corrupted the full integrity of the surface of the inside casing and the tips of the rotor vanes. These imperfections prevented the formation of a reliable oil film that was needed to maintain a vacuum seal while preventing surface contact to eliminate wear. Combined with the acidic oil, the resulting increase in higher operating temperature contributed to a breakdown of the phenolic/fiber composition of the rotor vanes. As the rotor turned, particles chipped off the trailing edge of the vanes and damaged the tips of the following vanes, which compounded the damage through increased vacuum leaks, pitting, and over-heating – leading to total vane breakdown, extensive case damage, and finally catastrophic failure.
Everything pointed to a high-temperature additive reaction as the problem. Dow Corning’s Technical Services staff suspected that a more benign lubricant would result in better performance by eliminating or changing the effects of the additives reacting with the process gasses, and attacking metal pump components. As a result, they recommended a low-additive mineral oil.
Traditional solvent-refined oils with zinc based anti-wear chemistry typically have a higher initial TAN (Total Acid Number). By comparison, the Molykote® brand mineral oils with zinc-free chemistry have a lower initial TAN. And, with less than 5ppm sulfur, its rust and oxidation preventative additives are virtually free of sulfur, so the oil is essentially a benign product that seemed to be a good fit. In addition, their special “engineered” chemistry makes them inherently more resistant to oxidation and emulsification, which enables them to last up to five times longer than conventional oils.
After plant maintenance professionals switched to the Molykote® formulation with benign additives and installed a larger oil pump, there was a 30% drop in surface operating temperature. While the exact cause of the temperature reduction was not known, both steps were contributing factors. The key problem solved, however, was the elimination of metal failure caused by corrosive additives.
Since switching over to the Molykote® brand oil the vacuum pump potentially has been operating smoothly, without incident and no breakdowns whatsoever.
The company is so happy with the results that they have decided to switch all of their vacuum pumps to Molykote®. In addition, they reduced the number of lubricants used in the building by almost 50 percent, from 13 competitive products to 6 Molykote® oils.
By reducing the number of competitive lubricants, they got additional efficiency improvements and simplifyied the purchasing process and reduced the potential for applying the wrong lubricants.
For more information about how Molykote® can avert or solve lubricant problems in your facility, contact IBT.
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To learn more about Power Transmission products from IBT, contact us today!
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