Analysis of Three-Body Abrasive Wear Damage in Journal Bearings of 1,050 MW-Class Ultra-Supercritical Steam Turbine

A high-vibration trip caused by excessive journal vibration displacement occurred in the journal-bearing lubrication system of a 1,050 MW-class ultra-supercritical steam turbine. The damage observed on the journal and bearing-metal surfaces included localized discoloration, circumferential scratches, abrasive wear, cutting marks, and scoring. The observed damage was attributed to three-body abrasive wear induced by hard metallic particles entrapped between the journal and the bearing metal. Thermal damage caused by insufficient lubricant supply was not the attributing factor. The foreign particles found in the journal-bearing lubrication system were identified as shot balls, shot grit, welding oxides, and bearing-metal wear debris. The hardness-ratio analysis of the journal-bearing lubrication-system components showed that shot grit had the highest wear-inducing potential, while the bearing metal exhibited the highest susceptibility to wear.