Case History: Cracked Bearing Race Detection In Wind Turbine Gearboxes

摘要

When properly implemented, acceleration enveloping is a very powerful tool for the early detection of rolling element bearing faults. Over the past year, new Bently Nevada ADAPT.wind. wind turbine monitoring systems were installed on several hundred 1.5 MW-class wind turbines. Shortly after deployment, some gearboxes exhibited similar vibration signatures. Spectral analysis of enveloped waveforms showed that the vibration frequency was associated with the high-speed downwind radial bearing inner race, and the raw accelerometer timebase waveform showed clear evidence of repetitive impact/ response vibration of very short duration. Vibration amplitude was not high enough to produce immediate concern, so the vibration was monitored over a period of several months. During this period, the vibration signature was observed to evolve slowly, with little change in direct vibration amplitude or frequency content, but with increasing impact/response complexity in the timebase waveform. When a newly installed turbine displayed similar behavior, the suspect bearing was removed and inspected. Four cracks were found in the inner race. After replacement, the vibration signals returned to normal. In this paper, after a brief discussion of implementation of the enveloping technique, we will show vibration data from two instances of these faulted gearbox bearings, describe the logical process used to diagnose the problem, and present confirming evidence.