Fatigue Reliability-based Inspection and Maintenance Planning of Gearbox Components in Wind Turbine Drivetrains

This paper introduces a reliability-based maintenance plan for wind turbine gearbox components. The gears and bearings are graded based on their fatigue damage and a maintenance map is developed to focus on those components with higher probability of fatigue failure and lower level of reliability. The main aim of this paper is to propose a method for developing the “vulnerability map” which can be used by maintenance teams to identify the components with lower reliabilities. The fatigue damage for gears and bearings are calculated at rated wind speed by the SN curve approach. The load duration distribution (LDD) method is used to obtain the stress range cycles for gears and load range cycles for bearings from the load and load effect time series obtained from a global response analysis. During routine inspection and maintenance, the vulnerability map can be used to find the faulty component by inspecting those with highest probability of failure rather than examining all gears and bearings. Such maps can be used for fault detection during routine maintenance and can reduce the down time and efforts of maintenance team to identify the source of problem. The proposed procedure is exemplified by a 750 kW gearbox and a vulnerability map is developed for this case study gearbox.