We are working with frame 9E DLN turbine in combined cycle. We are facing problem as follows:

One of the Primary flames is being re-ignited at base load with the intensity of 5000.

When load is reduced, flame is there in primary with the intensity of 2000.

We have checked the combustors with boroscope but find nothing abnormal.

Kindly suggest to us, what is the problem with our machine.

 

I would guess this DLN1. It's unusual to get it only on one fuel nozzle but basically it is a "flash back" to Primary, usually this can be caused by fuel pressure instability, large load swings and incorrect system calibration among many other things as well. As it is only on one combustion can, I would be doubtful how much you can really see with a boroscope, I think you need to pull this liner and fuel nozzles and have a close look.

 

You can check your flame scanner and calibrate them for accuracy of Flame Intensity Detection.
Another thing might have happened in your case that it is giving false information. i.e. It is actually not detecting any(or that much) intensity
but due to wriring problem like loose connection etc. may be the cause of this problem.

MMAhsan

 

Do you have reuter & stokes flame detecting system? Does the machine goes from Premix steady state to Extended lean - lean?
Is it only 1 chamber 1 /2/3/ or 14?
We had the same problem, and put refurbished liners in. Because there was flame-back from secondary to primary zone.

Success,
Carlos