W
We have four GE MS9001FA DLN2.0+ Gas-only 255MW gas turbines controlled by MarkV TMR Control System. We recently experienced two "Loss of flame" trips on the same unit (T1) during normal operation, and we are working on determining the root cause for that trip. LVDT error repeated itself for a long time before the first trip with the following alarm:
"TCQA LVDT position diff high REG#7"
Then loss of flame on cans resulted in trip.
361 27-AUG-2007 21:21:55.125 T1 L28FDA
FALSE EVENT Flame detector channel #1
362 27-AUG-2007 21:21:55.187 T1 L28FD
FALSE EVENT Flame Detected
363 27-AUG-2007 21:21:55.187 T1 L28FDB
FALSE EVENT Flame detector channel #2
364 27-AUG-2007 21:21:55.187 T1 L28FDC
FALSE EVENT Flame detector channel #3
365 27-AUG-2007 21:21:55.187 T1 L28FDD
FALSE EVENT Flame detector channel #4
385 27-AUG-2007 21:21:55.156 T1 0060
TRUE PALARM LOSS OF FLAME TRIP
After the first trip we just calibrated the LVDT#1 on PM4(G3) gas control valve.
Before the second trip in addition to the existing LVDT diff high alarm we received:
"TCQA LVDT regulator #7 feedback trouble"
alarm and we replaced the troubled LVDT. Following alarms occur before the second trip:
264 02-SEP-2007 19:05:24.125 T1 L28FDA
FALSE EVENT Flame detector channel #1
265 02-SEP-2007 19:05:24.125 T1 L28FDB
FALSE EVENT Flame detector channel #1
266 02-SEP-2007 19:05:24.187 T1 L28FD
FALSE EVENT Flame Detected
264 02-SEP-2007 19:05:24.187 T1 L28FDC
FALSE EVENT Flame detector channel #1
265 02-SEP-2007 19:05:24.187 T1 L28FDD
FALSE EVENT Flame detector channel #1
We suspect couple of problems that might cause the trip:
1) On second trip, LVDT #1 on PM1 goes bad, so valve could not follow the reference and the loss of flame occurs as a physical reality. LVDT #2 was working fine.
2) The idle time on <C> core of the unit T1 shows around 10 percent but the other three units indicate idle time around 22 percent. Right now there is no change on idle times.
3) We replaced the Reuter-Stokes flame detector module after the second trip but we are not sure if the module has gone bad. Is there a way to test the module in the workshop environment?
4) After the first trip, we removed all four flame detectors from the turbine and checked with light torch, and they function without any problems. So we put them back in. The cooling water supply was ok.
The unit is working for almost a week without any problems now. Any comments on understanding the reason would be most appreciated, thank you.
Regards,
"TCQA LVDT position diff high REG#7"
Then loss of flame on cans resulted in trip.
361 27-AUG-2007 21:21:55.125 T1 L28FDA
FALSE EVENT Flame detector channel #1
362 27-AUG-2007 21:21:55.187 T1 L28FD
FALSE EVENT Flame Detected
363 27-AUG-2007 21:21:55.187 T1 L28FDB
FALSE EVENT Flame detector channel #2
364 27-AUG-2007 21:21:55.187 T1 L28FDC
FALSE EVENT Flame detector channel #3
365 27-AUG-2007 21:21:55.187 T1 L28FDD
FALSE EVENT Flame detector channel #4
385 27-AUG-2007 21:21:55.156 T1 0060
TRUE PALARM LOSS OF FLAME TRIP
After the first trip we just calibrated the LVDT#1 on PM4(G3) gas control valve.
Before the second trip in addition to the existing LVDT diff high alarm we received:
"TCQA LVDT regulator #7 feedback trouble"
alarm and we replaced the troubled LVDT. Following alarms occur before the second trip:
264 02-SEP-2007 19:05:24.125 T1 L28FDA
FALSE EVENT Flame detector channel #1
265 02-SEP-2007 19:05:24.125 T1 L28FDB
FALSE EVENT Flame detector channel #1
266 02-SEP-2007 19:05:24.187 T1 L28FD
FALSE EVENT Flame Detected
264 02-SEP-2007 19:05:24.187 T1 L28FDC
FALSE EVENT Flame detector channel #1
265 02-SEP-2007 19:05:24.187 T1 L28FDD
FALSE EVENT Flame detector channel #1
We suspect couple of problems that might cause the trip:
1) On second trip, LVDT #1 on PM1 goes bad, so valve could not follow the reference and the loss of flame occurs as a physical reality. LVDT #2 was working fine.
2) The idle time on <C> core of the unit T1 shows around 10 percent but the other three units indicate idle time around 22 percent. Right now there is no change on idle times.
3) We replaced the Reuter-Stokes flame detector module after the second trip but we are not sure if the module has gone bad. Is there a way to test the module in the workshop environment?
4) After the first trip, we removed all four flame detectors from the turbine and checked with light torch, and they function without any problems. So we put them back in. The cooling water supply was ok.
The unit is working for almost a week without any problems now. Any comments on understanding the reason would be most appreciated, thank you.
Regards,