I
Our power plant (GE 9FA with Mark VI controls) had a trip last week on G3 purge pressure high.
After many checks we found that 2 of the 3 pressure switches (normally closed contact) had a high contact resistance - The contact resistance of switch A and C were in the K ohm range and seemed quite high in comparison to B which was 0.4 ohm. During operation we would get an alarm from one of the switches for some milliseconds before clearing. We have fitted a pressure gauge and checked the vent opening so we are sure it is not a real high pressure.
We have now replaced the pressure switches with new and the alarm has not been received since.
My question is - how / why would the Mark VI interpret the higher resistance of the A and C pressure switches as being and open contact?
Thanks for reading and hope you can assist.
Regards
Alan
After many checks we found that 2 of the 3 pressure switches (normally closed contact) had a high contact resistance - The contact resistance of switch A and C were in the K ohm range and seemed quite high in comparison to B which was 0.4 ohm. During operation we would get an alarm from one of the switches for some milliseconds before clearing. We have fitted a pressure gauge and checked the vent opening so we are sure it is not a real high pressure.
We have now replaced the pressure switches with new and the alarm has not been received since.
My question is - how / why would the Mark VI interpret the higher resistance of the A and C pressure switches as being and open contact?
Thanks for reading and hope you can assist.
Regards
Alan