Chemical factors for premature failures of roller bearings in wind turbines due to white etching cracks: A review from literature and industry experience

Abstract

This paper investigates the chemical influencing factors leading to premature bearing failures in wind turbine gearboxes. Chemical factors like the lubricant composition and the boundary layer of the bearing material play a crucial role in enabling premature failures caused by white etching cracks (WEC). They are then eventually triggered by energy input due to mechanical or electrical loads. Even though reproducing WEC on test rigs (e.g. FE8 test rig or three-disc-tribometer) is possible a reproduction or transfer of the knowledge to full-size test rigs or real systems remains challenging. This is due to the system-specific contact conditions which result from the respective loads, the bearing geometry and the chemical influencing factors. To collect the industry’s perspective on chemical influencing factors and their significance in the field, the state of the art was analysed and based on the results a survey was prepared. The survey interviews are conducted among leading manufacturers of lubricants, bearings, gearboxes and OEMs in the wind energy sector. From those results the influence of hydrogen, particles and contact temperature were identified as particularly important.