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BACKGROUND:
The gas turbine installed on site MS5001 having Mark-VI control system has 13 thermocouples installed on its exhaust. Upon the failure of one (ttxd_5), my understanding is that it should be declared unhealthy and removed from the spread calculation logic. However, the thermocouple's value (-17) is being read by the system and consequently spread value being shown is 426.3'C while the allowable value is 51.4'C
Please access the running logic values and cimplicity screenshot from the following link:
https://drive.google.com/open?id=0B-NCuP1kU4DMUUVBR21ac3pCUWM
ISSUE:
I need to know if this could trip the turbine on high spread reading? If so, is this an error on the programming part because the Turbine control system does recognize the thermocouple as unhealthy (logic snapshots are in the mentioned link)? Currently the exhaust spread security was forced on our turbine and so are some other exhaust thermocouple related securities based on the past experience of nuisance trippings. GEs workmanship issues were found to be the root cause earlier, and also the fact that Mark-VI even reads the transitional values of a failing thermocouple to generate trip signals.
The gas turbine installed on site MS5001 having Mark-VI control system has 13 thermocouples installed on its exhaust. Upon the failure of one (ttxd_5), my understanding is that it should be declared unhealthy and removed from the spread calculation logic. However, the thermocouple's value (-17) is being read by the system and consequently spread value being shown is 426.3'C while the allowable value is 51.4'C
Please access the running logic values and cimplicity screenshot from the following link:
https://drive.google.com/open?id=0B-NCuP1kU4DMUUVBR21ac3pCUWM
ISSUE:
I need to know if this could trip the turbine on high spread reading? If so, is this an error on the programming part because the Turbine control system does recognize the thermocouple as unhealthy (logic snapshots are in the mentioned link)? Currently the exhaust spread security was forced on our turbine and so are some other exhaust thermocouple related securities based on the past experience of nuisance trippings. GEs workmanship issues were found to be the root cause earlier, and also the fact that Mark-VI even reads the transitional values of a failing thermocouple to generate trip signals.