Posters

Abstract

1. Introduction Oil analyses are well established in the field of Oil & Condition Monitoring. They are the basis to make reliable statements concerning the condition of many applications and  its oil-lubricated components. Mineral oil based lubricants of API group I are more and more replaced by group II or III or fully synthetic fluids. The ageing process of those new fluids is different. Therefore it is a normal consequence that some of the well established methods to monitor the ageing process of the lubricant have to be proved.  2. Monitoring Oil Condition Typical, for mineral or synthetic oils established monitoring parameters are: * Viscosity * FT-IR Oxidation (Infrared spectroscopy) * Acid Number (AN) * Colour * Element analyses  IN MODERN, SYNTHETIC OILS THERE ARE SAMPLES IN WHICH THE VALUES AND THE FT-IR SHOW NO CONSPICUOUS CHANGES REGARDING AN INCREASING OIL AGING. AT A CERTAIN TIME SOME WEAR VALUES, ESPECIALLY NONFERROUS METALS, BEGIN TO INCREASE WITHOUT A CLEAR VISIBLE REASON. A TRENDLINE OF SUCH SAMPLES OFTEN REVEALS A DARKENING OF THE OIL, WHICH IS NOT COMPULSARY UNUSUAL. SOME POSSIBLE REASONS ARE PARTICLE CONTAMINATION OR MIXTURE WITH ANOTHER LUBRICANT. BUT EVEN A VERY NORMAL AGING PROCESS GOES ALONG WITH DARKENING OF THE OIL. HENCE, THE CHANGE IN COLOR IS NOT A VERY PRECISE HINT FOR A CRITICAL CHANGE IN THE OIL CHEMISTRY. IN COMBINATION WITH DARKENING OF THE FLUID AN INCREASE OF COPPER (AND ZINC) CAN OFTEN BE OBSERVED IN OIL SAMPLES OF MAIN GEARS. THE INCREASE OF THE WEAR SITUATION HAPPENS SOMETIMES IN A QUITE SHORT PERIOD OF SEVERAL MONTHS. ACCORDING TO HIGH COSTS FOR AN OIL CHANGE OR SOME OTHER MAINTENANCE ACTIVITIES IT IS AN IMPORTANT SUPPORT TO HAVE AN INFORMATION BEFORE A CRITICAL WEAR SITUATION EXISTS. AN EARLY-STAGE-DETECTION GIVES THE OPERATOR TIME TO REACT ON IT AND TO PLAN SOME MAINTENANCE ACTION. FOR SUCH CHANGEMENTS THE CLASSICAL ANALYSES METHODS ARE NOT SUFFICIENT TO DETECT THE BACKGROUND OF IT. With the High Pressure Liquid Chromatography (HPLC) the degradation of nonferrous metal passivators can be made visible. For these analyses we want to identify and monitor the shift of these inhibitors in a standard laboratory analysis. The degradation of the inhibitor allows the non-ferrous metals to increase in the gearbox and can therefore provide far-reaching information. This is a possibility to detect those changes in the oil chemistry in an early stage. 3. Conclusions The presentation shows examples from wind turbines to show methods and how analyses help to overcome the situation. A monitoring of nonferrous metal passivators with the HPLC support the operator to detect critical changes. Not any single parameter is able to monitor reliable the oil condition for all kind of fluids and applications. Therefore the main challenge is to find the right mix of methods to evaluate the oil condition of wind turbine gear oils. The mentioned HPLC method is a further tool to secure the operation of wind turbine gearboxes.