GE 9FA DLN II combustion trouble 1

[stratford]

Good evening to all. On site we have a Gas Turbine GE 9FA DLNII. SOme time before we noticed a sudden loss of flame to one of the 4 flame detectors, after one minute we hde high exhasut spread temperatures and consequent trip of the turbine. When we put back the unit it seemed OK. Can you suggest for a possible cause?

 

[Romefu12]

Stratford
Diagnostics of the 9FA and DLN 2.0 takes some rather substantial expertise and a host of data download of the event from the control, Mark VI is presume and a host of control tags to determine what actually happened to give you a loss of flame and subsequent HETS trip. You would need to know many conditions such as DWATT Load, DLN Mode, was the unit transfering mode at the time and lengthy list of the control tag data. Have you tried asking GE to diagnose?

Kind Regards
Romefu12

 

[stratford]

Romefu12, thank you very much for your answer. During trip from eaxhasut t/c sread we have noticed only that one of the flame detectors 28FD-15 showed 0 and as a consequence we had the exhaust spread and the trip. Load was steady, gas flow the same.
We suspect that one combustion chamber went OFF.
Does this make sense?

 

[rmw]

That is exactly why you have the control logic that you do because you can suffer a flame out in only one combustion can while still maintaining flame in the others. It may or may not be one with a flame detector depending on your turbine. A significant exhaust temperature spread will be an indicator of this, and that is why the logic takes it out.

rmw

 

[Romefu12]

Stratford
It is not unusual for 1 can to suffer a flame out. If you do suffer a flame out you will create a substantial High Spread. You need to download the Exhaust Thermocouple Spread data during the event (Control Tags TTXD1 thru TTXD27) and your FD_INTENS_1 thru FD_INTENS_4 to determine when you lost the flame sensor data. I suspect if you lost flame the control would interpret this event as a cold spot. If you could tell me at what Unit Load and what type of fuel was being used when this happened I could probably tell you which combustion can or cans to inspect thru a predicted swirl calculation. This could be a hardware issue, a fuel contamination issue, or other mechanical issue with the purge circuit. Many things could cause this issue.
Romefu12

 

[stratford]

Romefu12, seconds before the fault the load of Gas Turbine was 260MW (base load), flame intensity was 61-63-60-58 on the four detectors, then we had L28FDD alarm (detector 4 went to 0), then COMBUSTION TROUBLE and finally HIGH EXHAUST TEMPERATURE SPREAD TRIP. The spread was caused by Exhaust TC 17. Also if you can you can send me this swirl?
Thank you in advance. Our GE support suspect also fuel contamination on the cans.

 

[stratford]

Also romefu12, the flame is lost before the spread and the fuel in natural gas (coming from Russia). We only this GT only in natural gas due to several technical problems with liquid fuel.

 

[Romefu12]

Stratford
Your L28FDD alarm indicates loss of flame in Can 8. However your HIGH EXHAUST TEMPERATURE SPREAD TRIP caused by Exhaust TC 17 indicates a swirl calculation @260 MW to indicate a problem with Can 4.

I would begin by borescope inspection of cans 3,4, 5, and 8.

Romefu12

 

[samson16]

Dear Mr. Romefu12,
The conversation was quite informative and useful
Could u please post the Swirl chart (Load vs Swirl angle graph)for this machine. I was a startup TA in GE few years ago and now I am a freelancer

Thanks and warm regards
Samson16