ABSTRACT
This troubleshooting case study was precipitated by a large steam turbine bearing problem. In this case, a potential shortcoming of the high-pressure-turbine pivoted-pad journal bearing configuration was discovered. During periodic inspection of steam turbine internals at 5-year intervals, several high-pressure turbine pivoted-pad journal bearings showed severe fatigue damage to the leading edge of the white metal babbitt liners on the unloaded bearing top pads. In response to this, the author developed a simulation vibration model for statically unloaded single tilting pads. With that simulation model, it was discovered that under certain pad design and operating conditions, a statically unloaded pivoted bearing pad could exhibit a subsynchronous self-excited pad flutter vibration that produced dynamic loading spikes on the pad lead edge. Furthermore, it was determined that this self-excited pad flutter occurred only when there was no stable static equilibrium position for the pad within its displacement space. The details of the nonlinear time-transient vibration simulation results are presented with insightful physical explanations.
