Failure Analysis on the Thrust Wear Detector of Turbine in Nuclear Power Plant

1GME037MV is the thrust wear detector of turbine.Before the turbine run up,the value of this channel often fluctuated.The engineer checked the channel,terminal,continuity,insulation,and driver and so on,no problem was found.At last,when disconnecting the end of the detector from the driver,then re-connected the end to the driver,the channel value is OK,after a while it became wrong again.Measured the resistance of the detector,it is 13O hm when the channel is OK,and 76 Ohm when the channel is wrong.According to the result of the checked,the conclusion is the character of the detector had changed.Both the measured value GME037MV and GME038MV are high 0.7mm,the turbine will trip,In the end the detector of GME037MV was replaced when the unit shut down.