A critical Turbocompressor at the Olefin Plant in Tarragona, Spain, experienced random vibration spikes in the steam turbine during steady-state operation, causing alarms and occasional trips. Vibration analysis showed fluctuations in 1X forward precession vibration, likely due to rotor thermal bow from rub events. The amplitude and phase of these spikes increased over time, eventually triggering trips.

Investigation ruled out causes like rotor imbalance and extreme shaft position. Instead, the issue was traced to reduced clearances from carbonized oil deposits in the NDE bearing seals, causing periodic rubs. To address this, an air hose was installed to cool the steam labyrinth, and adjustments to the gland steam system stabilized vibration.

This case demonstrates the importance of monitoring oil seal conditions, as carbonized deposits can reduce clearances and increase vibration. Proactive cooling and vacuum adjustments can mitigate these risks and maintain Turbocompressor reliability.