Vibration Alarm Analysis and Treatment of Main Coolant Pump in Nuclear Power Plant

The structure of main coolant pump in a nuclear power plant and vibration alarm are introduced. Vibration analysis and trouble diagnosis have been carried out. It shows that pump shaft vibration is mainly composed of running frequency (1×) and half of running frequency (0.5×), motor shaft vibration is just composed of 1×. The vibration fluctuation in pump shaft is caused by the variation of amplitude in 0.5×. Based on vibration analysis result, the fault investigation has been launched, in which it includes installment, measurement, dynamic balance and pump design. After detailed investigation, the excessive vibration was induced by the dynamic unbalance of pump shaft and unsteady vortex of shaft seal water. The research for treatment has been implemented on dynamic balance and seal water flow. It is suggested to increase the seal water flow to control vibration fluctuation. The result shows that this method is effective, economical, safe, and very easy to implement for suppressing flash vibration alarm.