Posters

Abstract

Rolling-element bearings at the high-speed end of the wind turbine are relatively easily monitored for early fault detection and diagnostics. Moreover, the bearing fault mechanism and its stages of degradation are well understood and lead-time to service is fairly accurate to predict. Loose bearing races, however, present more of a challenge for both detection and forecasting replacement. Moreover, the consequences of not taking corrective action can be very costly. If the outer race is loose, there is a risk that it will rub against the gearbox casing bore, thereby enlarging it. This cannot be repaired up-tower. If the excessive clearance is not detected and corrected in time, the parallel stage shafts can then become misaligned and result in tooth damage as well as damage to the other bearings. If a fractured tooth falls between two meshing gears, the gearbox casing can crack. Inner race looseness, also called bearing creep, can also occur, and is sometimes caused by a crack in the inner race. Inner race looseness, if not corrected, can wear out the surface of the gear shaft where the bearing is mounted. The entire gearbox has to be replaced if the shaft is damaged. A case study is presented for both outer and inner race bearing looseness, both of which occurred on the IMS of the parallel gear stage of the wind turbine gearbox. Measurement techniques for detecting this condition are presented, together with photos after disassembly and an analysis of the results.