GE 7FA Gas Turbine Dynamics

Hello,

I am new in that forum and we are looking for an answer about GE's OpFlex AutoTune DLN2.6+.

For the last two days we getting high dynamics on only one can. The alarm is L30C14A14H "HI COMBUSTION DYNAMICS CAN 14 SCREECH". All other cans are normal.

Please, could someone explain to us what that means and what could be at risk?

Thank you.
Frank
 
Frank,

What are the emissions doing--are they normal or are they higher or lower than normal (particularly the NOx and CO--coming out of the turbine)?

When did this start? After a trip from load? After a maintenance outage?

Has anyone tried replacing the combustion dynamics sensor on combustor 14?

Does this only happen at Base Load, or high loads, or medium loads, or???

Are there any Diagnostic Alarms associated with the CDMS (Combustion Dynamics Monitoring System)?
 
>What are the emissions doing--are they normal or are they
>higher or lower than normal (particularly the NOx and
>CO--coming out of the turbine)?
Both are normal.

>When did this start? After a trip from load? After a
>maintenance outage?
After an outage.

>Has anyone tried replacing the combustion dynamics sensor on
>combustor 14?
Yes, they changed the probe. But we got high dynamics before and now they are higher.

>Does this only happen at Base Load, or high loads, or medium
>loads, or???
All over the place.

>Are there any Diagnostic Alarms associated with the CDMS
>(Combustion Dynamics Monitoring System)?
We lost one DWATT sensor.
 
Frank, since you indicated this began after an outage I would suggest that something may have not been assembled correctly or was damaged. I am making a lot of assumptions in my response. There have been several variations of the CDMS probes and configuration through the years. I am assuming you have a newer system that has the CDMS probe mounted at the combustion can and then wired to a junction box outside the turbine compartment that houses the amplifier modules that are then wired to the CDMS terminal board. But if you provide more detail of your exact system we can be more precise.
Make sure that the sensor and the attenuator can (looks like a soup can wrapped with tubing) are properly installed on the combustion can. The sensor needs to be installed properly in the attenuator can, the nut that secures it should be torqued to 20 ft/lbs and safety wired. Next issue is sometimes with the connector and wiring that feed from the sensor to the amplifier module.
If your emissions are normal, and all the dynamics in the other cans are normal, then most likely it is just an issue with the sensor or wiring. Especially if you did not have this problem prior to the outage. Please provide more detail and we can try to assist further.
 
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Frank, since you indicated this began after an outage I would suggest that something may have not been assembled correctly or was damaged. I am making a lot of assumptions in my response. There have been several variations of the CDMS probes and configuration through the years. I am assuming you have a newer system that has the CDMS probe mounted at the combustion can and then wired to a junction box outside the turbine compartment that houses the amplifier modules that are then wired to the CDMS terminal board. But if you provide more detail of your exact system we can be more precise.
Make sure that the sensor and the attenuator can (looks like a soup can wrapped with tubing) are properly installed on the combustion can. The sensor needs to be installed properly in the attenuator can, the nut that secures it should be torqued to 20 ft/lbs and safety wired. Next issue is sometimes with the connector and wiring that feed from the sensor to the amplifier module.
If your emissions are normal, and all the dynamics in the other cans are normal, then most likely it is just an issue with the sensor or wiring. Especially if you did not have this problem prior to the outage. Please provide more detail and we can try to assist further.
Thank you for your answer.
We opened a case with GE services and they came up with the same conclusion.
In our next shut down we we are going to replace the probe.
Frank
 
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