Micropitting mitigation in wind turbine main bearings through laboratory and field testing of an advanced rescue grease

Abstract

The micropitting behaviour of eight greases has been investigated for wind turbine main shaft bearings. Results reveal that micropitting resistance is not solely governed by base oil viscosity as low and medium viscosity greases outperform higher viscosity ones. Special tests have been carried out to investigate the effectiveness of rescue grease in mitigating surface damage progression. Controlled predamage phases have been introduced using a low reference grease to simulate varying severity levels, followed by application of rescue grease. Both laboratory and field evaluations demonstrate that rescue grease effectively suppresses the progression of surface damage, evidenced by reductions in bearing temperature and vibration levels. Surface analyses revealed that rescue grease promotes polishing of existing cracks and prevents further propagation. Comparisons across different scenarios confirm its ability to stabilise tribological performance and preserve surface integrity over extended cycles. Together with field case studies showing that early introduction of rescue grease delays damage escalation and maintains stable bearing temperatures, these findings highlight the potential of rescue grease as a proactive and practical solution for extending component life in demanding wind turbine applications.