We have two 7FA gas turbines which are operating at Base load. It was observed that the Flame intensity of GT-2 increased by 10% for all detectors and became normal after some time say 10 to 15 min. This happened 3 times in 3 hrs span. It was also observed that Nox value also raised by 5-6 ppm in the same time. To be simple, spikes in Flame intensity and Nox values were observed. The other machine has no problem.

We checked the Fuel gas quality, P2 pressure, Exhaust TC readings but they do not show any spikes. The machine was operating at base load that time and the load was changing according to the ambient temp. Both machines load trend shows the same pattern.

Some colleagues say it is just a software (??)problem as the Nox value came back. Can anybody explain what could have happened?

Is anybody having idea what could have happened? If you need more data please let me know,I will post it.

Thanks,
Ravi Kishore

 

You neglected to inform us of the type of combustion system on you turbines--DLN or conventional (non-DLN).

Since the turbines likely have DLN combustors, the problem is most likely that something caused the fuel splits to change for those periods of time which caused more fuel to be burned in the diffusion flame ("pilot flame"). The load wouldn't change very much if this were to happen, but the emissions, and possibly the flame intensity, might.

If you have trends of fuel splits and valve positions, that will likely tell the tale of what happened. You'll just need to try to determine what caused the split to change....

 

Thanks CSA for reply.I didn't expect that 7FA may be there without DLN,that's why I did not mention.

We checked the trends for All GCV position trends but they did not show any change.I will once again check them and give feedback.

Thanks,
Ravi Kishore.

 

Dear CSA,

I checked the PM1, PM2, PM3 & Quat GCV position trends. There was no abnormality observed. I got the trends only for PM3 Schedule 2 Split with Bias (FSRPM3S2_BA). The trends did not show any change. What else shall I check?

Thanks,
Ravi.