Wind Turbine Main Bearing Reliability Analysis, Operations, and Maintenance Considerations: Electric Power Research Institute (EPRI)

Wind turbine main bearing failures are one of the primary reasons for the increase in operations and maintenance (O&M) costs and turbine downtime, especially on the newer and larger onshore wind turbines (2X - 6X MW fleet). Turbine OEMs purchase main bearings from a supplier with limited visibility on design and manufacturing quality. Bearing parts (inner race, outer race, cage, and rollers) typically get manufactured at various locations around the world leading to more uncertainty in quality and life. It is important for owners/operators to know the impact of these design and manufacturing issues on the turbine operational costs. In addition to the design and quality, turbine model, drivetrain assembly (blades, pitch, hub, mainshaft, and gearbox), lubrication system, grease properties, and operating conditions have a significant impact on the main bearing life. This paper addresses these issues and includes onshore main bearing reliability analysis, failure mechanisms, damage modes, life impacting factors, maintenance best practices, and mitigation strategies to extend the life and reduce O&M costs.