S
Hi,
Background:
We have two GE Frame 7B turbine (converted to EA when we purchased them) running on natural gas. We run in peaking mode, so winter runs are typically minimal. We did emissions tuning in spring of 2012 on both units and ran heavily in summer of 2012 with no issues. This problem started occurring around April 2013 on only one of the units.
Problem Description:
After light off (900rpm), the unit will spool up to just below 1000RPM when the high pres. trip oil pressure starts dropping (as seen on the gauges at the gas control house and on the turbine accessory compartment). It goes from about 1300PSI down to 400PSI. The hydraulic oil pressure gauge in the sump indicates that it remains at 1500PSI throughout the startup and trip.
Approximately 15 seconds after the pressure starts dropping, the SRV valve closes. 4 seconds later, the GCV closes and we get a loss of flame trip at the same time. No other trips or alarms are present. We have RPM, SRV position, GCV position, and trip timestamps from probably 12+ different occurrences of this trip and they are all basically the same.
The trip oil pressure does NOT drop instantly. It takes about 10-15 seconds to reach 400PSI, which is approximately when the SRV closes. We don't have a trip oil pressure transmitter, so this is approximate.
Finally, this problem does not occur consistently. Sometimes the unit starts right away, sometimes it starts after one trip, and sometimes it takes multiple starts.
Other Info:
SRV and GVC calibrations both check out OK. We have stroked both valves
We have an L63QA (Lube Oil Pressure Low) alarm come in approximately 2 minutes before the loss of flame alarm. From our drawings, it appears to be unrelated.
We have confirmed that our dump and trip solenoids are not causing this issue.
What would cause this type of pressure loss, and what can we do to trace it down?
Thanks,
Stephen
Background:
We have two GE Frame 7B turbine (converted to EA when we purchased them) running on natural gas. We run in peaking mode, so winter runs are typically minimal. We did emissions tuning in spring of 2012 on both units and ran heavily in summer of 2012 with no issues. This problem started occurring around April 2013 on only one of the units.
Problem Description:
After light off (900rpm), the unit will spool up to just below 1000RPM when the high pres. trip oil pressure starts dropping (as seen on the gauges at the gas control house and on the turbine accessory compartment). It goes from about 1300PSI down to 400PSI. The hydraulic oil pressure gauge in the sump indicates that it remains at 1500PSI throughout the startup and trip.
Approximately 15 seconds after the pressure starts dropping, the SRV valve closes. 4 seconds later, the GCV closes and we get a loss of flame trip at the same time. No other trips or alarms are present. We have RPM, SRV position, GCV position, and trip timestamps from probably 12+ different occurrences of this trip and they are all basically the same.
The trip oil pressure does NOT drop instantly. It takes about 10-15 seconds to reach 400PSI, which is approximately when the SRV closes. We don't have a trip oil pressure transmitter, so this is approximate.
Finally, this problem does not occur consistently. Sometimes the unit starts right away, sometimes it starts after one trip, and sometimes it takes multiple starts.
Other Info:
SRV and GVC calibrations both check out OK. We have stroked both valves
We have an L63QA (Lube Oil Pressure Low) alarm come in approximately 2 minutes before the loss of flame alarm. From our drawings, it appears to be unrelated.
We have confirmed that our dump and trip solenoids are not causing this issue.
What would cause this type of pressure loss, and what can we do to trace it down?
Thanks,
Stephen