Dear Sir,

We are having 2 GE frame 7FA with DLN 2.6 technology gas turbines.
As we are receiving the Natural Gas from different gas plants, the natural gas parameters usually changes frequently,

Based on LHV & specific Gravity of natural gas changes, the Heating contro v/v output changes to increase/decrease the fuel gas temperature accordingly. to minimize the upset, we incorporated the logic to clamp the value when LHV reaches to 930 BTU/SCF on low range & 1310 BTU/SCF at high range. also specific gravity value will clamp at 0.65 at high range & 0.5 at low range.

Currently the natural gas specific gravity is high (>0.65) so both LHV & SG values clamped at 930 BTU/Scf & 0.65.

But the actual LHV is 1000 BTU/scf & specific gravity is 0.69.

In this case, the fuel gas temperature is maintaining bases on clamped values but not actual values.

I want to know that will it harm the Combustion hardware?

 

I am just becoming familiar with the effects of varying Wobbe indices on turbine operation and don't have a lot of experience with it to date. But, I have to say from the importance placed on it by GE and other combustion turbine manufacturers it would seem that the operation you describe can lead to some premature turbine hot gas path part failures. You should really be asking this question of GE as they have the best ability to respond with their view of how operation outside the limits of expected Wobbe indices will affect the turbine and its components.