Failure analysis and on-site rectification of wind turbine pitch bearing ring cracking

As a key component of wind turbine, the reliability of pitch bearing affects the safe operation of the turbine. The ring cracking is a common failure mode in recent years. Aiming at the actual failure case of a double-row four point contact ball pitch bearing ring cracked in a wind field, this paper firstly analyzes the macro morphology of the cracking fracture and preliminarily determines the damage type of the ring cracking. On this basis, the plug hole fatigue problem is focused and solved with proposed global model—sub model FEA technique; the quantitative influence of processing defect (scratches) on plug hole is analyzed based on fracture mechanics for the first time, highlighting the importance of eliminating minor defects such as scratches during the bearing manufacturing process. For in-service turbines, bearing redesign and batch replacement will lead to huge economic losses. An innovative on-site retrofitting solution with stepped flanges is proposed, which not only resolves the reinforcement issue of the bearing ring but also addresses the fatigue problems caused by the localized stiffness caused by the flange. The research results provide a method reference for the fatigue assessment of the ring at the design stage of the pitch bearing. It also provides a feasible scheme for the risk elimination for the pitch bearing operating in field.