After HGPI of gas turbine which MS5001P, the machine was started up and difficult to fire due to low gas pressure (17 bar) and alarm is 16 bar. control guy did some adjustment at control site, the problem came up after 1 week operation the flame detector suddenly were not detected the flame and lead to unit trip. investigation was made to resolve the problem and found some liners were out of alignment. What cause of this problem? Can low fuel gas pressure lead to liner vibration or combustion dynamic problem increasing pulsation in the combustion can?

 

You must increase line pressure set point, significantly, at the pressure reducing station.

Once gas is flowing, pressure will drop somewhat due to pressure loss in the gas line, which causes the trip.

 

Huh?

If the original posting is understood correctly there was more than sufficient pressure during starting; it was just above the alarm setpoint. So, the unit should certainly have been able to start and run at rated load with gas fuel pressure just above the alarm setpoint. (The SRV might have been at or near 100% open, but the unit should still have started and run.)

Low gas fuel pressure--as described--during starting could not cause the kinds of mechanical conditions described. If the unit was started and running, and then flame was lost for some reason (which would indicate either that fuel flow/pressure was not sufficient to maintain flame at speed or that the liners simply collapsed and blocked flame--it's not clear from the original posting) the problems are not likely related to low gas fuel pressure.

It's more likely that there was some problem with the fuel nozzles and the mechanical reassembly or with the materials used in the construction or refurbishment of the hot gas path components that led to difficulties firing the unit (establishing flame) and in the mechanical "misalignment" alluded to.

Flow and pressure are definitely related; if the piping and components are not sized properly then as flow increases pressure will decrease. But, the unit was running before the HGPI, so those issues should not be a concern.

The GCV and the SRV would have to be fully open (100%) and the unit load would have to be much less than rated for any type of combustion problem like was alluded to to even have a chance of occurring. There would likely be many Process- and Diagnostic Alarms alerting a conscious operator and -supervisor(s) to problems with fuel supply long before the hot gas path components "failed" however they "failed"--and not because of pressure pulsations or liner vibrations.

Poor assembly techniques and low-quality hot gas path components are the most likely problems--<b>from the information provided</b>.