dear all, please clarify my doubt.
suppose a gas turbine (Combined cycle) was operated at baseload in the month of May when the ambient temperature is around 40 deg C and RH 20% PRESSURE- 1010.00 mbar. And the same gas turbine operated at baseload in October end when the ambient temperature is around 25 deg C and RH 50% PRESSURE- 1005.00 mbar. And during winter time the corrected output (correcting to site conditions) is 4 to 5 MW less than the previous baseload (i mean May). How can we compare the October base load test data with May month base load test data? if we compare output means its okay as it is corrected to the site conditions. and we experience around 4 MW less.
No major outage taken place in between, two tests difference in FFH is less than 700 FFH, wash done some 10 days before the each test. how can we compare and how to find for wat reasons the gas turbine corrected output is reduced by 4 to 5 MW?
My doubts are:
How much of the rated output of the supposed gas turbine does 4-5 MW represent? 20% 10%?5% 3%?
Do you have the correction curves for the supposed gas turbine? If so, have you applied the correction(s), and what do the corrected data indicate? (Correction curves can include the number of starts/stops and trips.)
How long has it been since the supposed gas turbine had a thorough off-line compressor water wash, including the inlet guide vanes? (You mentioned washing, but didn't say if it was on-line or off-line.)
What is the inlet air filter differential pressure change over the time period in question?
How long has it been since a maintenance outage?
How long since the inlet air filters were replaced?
What is FFH?
Has the fuel source changed in the time period in question?
How frequently is the supposed gas turbine started?
How frequently does the supposed gas turbine trip from load or while starting?
Have the inlet guide vane LVDT(s) been calibrated recently? If so, why?
Does the unit exhaust to atmosphere or through an HRSG (Heat Recovery Steam Generator)? Does the unit have a bypass stack, and, if so, are you comparing output at the same conditions?
Do you have axial compressor discharge pressures for the various times in question? If so, how have they changed over time?
We're the axial compressor discharge pressure transmitter(s) calibrated during the time period in question? If so, why, and did the calibration change, and by how much?
Do you have fuel flow-rates for the various times in question? If so, how have they changed over time?
Do you have exhaust temperature readings, including spreads, for the time period in question? If so, how do they differ over the time period in question?
Are you certain the supposed gas turbine was operating at Base Load and not on any other operating mode/control for all data points?
There are a LOT of factors that can affect turbine output, and the above are just a sampling. Axial compressor and turbine internal clearances can change over time and depending on the turbine they can have a significant effect.
We would very much like to our doubts cleared with full answers to all the questions.
So, I think the FFH comment was trying to say the difference in Factored Fired Hours between the two times was 700.
700 can be a lot on a machine which is started multiple times and which has not had a thorough off-line compressor water wash, and which has not had a major maintenance outage in some time.
But, we need more detailed information to satisfy our doubts. When will we get the detailed information that was requested?
That is the question now.