Proper lubrication of wind turbine main shaft bearings are key to the efficiency, reliability and safety of the system. During its service life, bearing grease will degrade, congeal, harden and restrict lubrication of critical components. These issues are often reflected in overall increase to turbine operating temperatures and vibration potentially resulting in premature failure of the bearing. Flushing/purging alone is rarely effective due to flow restrictions and fluid properties so traditionally the bearing must be disassembled to manually scrape away the hardened grease.
AFP has partnered with Ocean Team to offer a new patented grease replenishment program that targets old and hardened grease. The program delivers an effective and safe solution for bearing maintenance with minimal downtime.
Our client is major power generation operator and asset services provider, maintaining multiple wind farms across Australia. Following a recent critical failure of a turbine bearing, they approached AFP and Ocean Team when other turbines in the park began displaying similar performance trends.
Inspection of the failed turbine bearing revealed hardened/congealed grease to be the principal cause of failure with significant defects to the bearing’s outer race. Where the grease has hardened in the gallery, grease flow to the loaded zone was restricted. As shown in the below graphs, drastic temperature and vibration increases were observed and reached critical levels before the turbine was placed on restricted operation.
Unless immediate maintenance measures were taken for the other operating turbines, power restriction must also be applied to prevent accelerated damage to the bearing system. Condition monitoring recorded temperatures up to 20 °C above the park average, reaching a maximum of 70°C under high wind loads. Attempts to purge the system with traditional flushing methods were unsuccessful with the new grease rapidly degrading under the high temperatures.
AFP’s grease replenishment program can be tailored to a wide range of bearing and grease systems. To ensure compatibility with the solvent fluid and best flushing outcomes, laboratory tests are performed system contamination levels and grease properties.
Key project stages include:
- Bearing flushing unit is connected to bearing grease points to efficiently clean and replenish the system in a single set up.
- Injection of a solvent fluid to dissolve old and hardened grease
- Flushing with turbulent flow and filtration of the bearing system to remove contamination and old grease
- The bearings are free of grease, providing an excellent opportunity for visual inspection of the bearing’s condition
- Fresh grease is added to the clean bearing system
- Trend analysis for preventive maintenance: effective condition monitoring to prevent accelerating wear and anticipate breakdowns going forward
- Turbines were able to resume operating at full capacity following successful completion of the grease replenishment program
- Efficiency gains and a 15% (8°C) drop in operating temperature, bringing this in line with the park average
- Trend analysis of temperature and vibration confirms performance indicators are no longer tracing path to critical failure
- Maintenance interval is extended until change out can be scheduled