Main bearings have high radial load capacities and an advanced tolerance for large misalignment. However, most main bearings still fail prior to their 20-year design life.
High axial loads on the rotor and main shaft during load exchanges, from downwind to upwind, cause an uneven distribution of weight beyond design limitations.
The main bearing's Achilles Heel is its susceptibility to Heathcote slip, which occurs when there is an interfacial slip between the ball and the groove caused by insufficient lubrication. Main bearings are prone to this type of sliding because of a loss of lubrication during axial displacement and/or insufficient lubrication due to low RPMs (revolutions per minute). This increases metal on metal contact, which intensifies its risk for micropitting and wear.
Dr. Nick Weinzapfel, Chief Materials Scientist for Bearing Dynamics, and his team of bearing specialists applied the core capabilities of DigitalClone to analyze main bearing failure modes. The new main bearing wear model predicts when failures will occur in operational wind turbines based on material quality and physics-based and tribological assessments of the whole system dynamics. Life extension actions are recommended to prevent premature failures.
Weinzapfel will present the new main bearing wear modelling technique at the National Renewable Energy Laboratory’s Drivetrain Reliability Collaborative Meeting on Wednesday, Feb. 22.