What are the critical failure modes of a hydro-generator's bearings?

Critical failure modes of hydro-generator bearings include fatigue failure, lubrication failure, contamination, and excessive vibration. Fatigue failure occurs when the bearing material experiences repeated stress cycles, leading to crack initiation and propagation, eventually resulting in spalling or flaking of the bearing surfaces. Lubrication failure happens when the oil film separating the bearing surfaces breaks down, leading to metal-to-metal contact, increased friction, and rapid wear. This can be caused by insufficient oil supply, oil contamination, or oil degradation. Contamination of the bearing lubricant with dirt, water, or other foreign particles can accelerate wear and reduce bearing life. Abrasive particles in the oil can scratch and damage the bearing surfaces, leading to increased friction and heat generation. Excessive vibration, caused by imbalance, misalignment, or external forces, can impose high dynamic loads on the bearings, accelerating fatigue failure and reducing bearing life. For instance, water hammer in the penstock could cause excessive vibration. Each of these failure modes can lead to increased bearing temperature, noise, and vibration, eventually resulting in bearing seizure and generator failure. Monitoring bearing temperature, vibration, and oil condition is essential for detecting early signs of bearing distress and preventing catastrophic failures.