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The GE 7EA User Group met this month in San Antonio, Texas. The event kicked off with a reliability day and a presentation on oil analysis, and some key points were made. One of the points was that the primary reasons for oil analysis failure were that the vendor takes too long doing the analysis, and user delays in sending the samples. By the time the results are in, they are meaningless as too much time has elapsed.
Another surprising revelation was that oil samples arrive in old water bottles and Gatorade bottles. That results in a contaminated sample. Interestingly, samples of hundreds of companies highlighted a growing trend towards varnish problems in more and more turbo machinery applications. Varnish often leads to trips and is hard to detect using standard tests.
Dow Chemical followed with a possible solution. Instead of using mineral oils or synthetics which are both hydrocarbon based, the company is promoting Polyalkylene Glycol (PAG) based synthetic turbine fluids as a non-varnishing lubricant for gas and steam turbines. It has been used for years in metalworking fluids, fire resistant hydraulics and gear oils, and now it is invading the
turbo machinery sector.
High temperatures are believed to be one of the key factors leading to oxidation. Oxidation creates decomposition byproducts of high molecular weight and the agglomeration of salt contaminants. This is what forms an insoluble varnish that adheres to surfaces. With PAGs, however, every third atom is oxygen, and this provides polarity which promotes its non-varnishing capability. This approach has been applied by Dow to four sites using a variety of gas turbines for the last few years.