Our gas turbine is frame 5 (5002) compressor driving, the last start up was reached 85% of speed (TNH) and it couldn’t reach 100%. It was tripped by not reach full speed no load.

Is there any constant to check

 

When did the problem occur: After a maintenance outage? Were any LVDTs calibrated during the maintenance outage? What controls work was done during the maintenance outage? What mechanical work was done during the controls outage?

You should be comparing this start-up to one that was successful, looking at FSR and second-stage nozzle angle and LP shaft speed (TNL) as well as HP shaft speed (TNH).

To answer your question about checking Control Constants, no. If the unit has been working properly prior to this last start-up, and nothing has been done to change any of the Control Constants, then the Control Constants are not suspect.

If a machine fails to accelerate it's likely because of a lack of fuel. That could be caused by many problems.

What Diagnostic Alarms were annunciated during the start attempt? What Diagnostic Alarms were present prior to the start attempt?

What Process Alarms were annunciated during the start attempt?

When does the LP shaft usually break away from zero speed during a successful start? What was the LP shaft speed during the failed start?

But to answer your question about checking Control Constants, unless someone has changed something it's not likely the problem is a Control Constant.

 

You don't provide enough information! Has this problem occurred before? What was the LP shaft speed? Has any maintenance been done just prior to this start? Absent any other information, first place I would look is the 2nd stage nozzle control, which controls the energy split between the HP and LP shafts. Check the position feedback (LVDT) on the 2nd stage nozzles.

What version of control (Mk II, IV, V or VI)? Was anyone changing constants? (If it worked before, and no constants have been changed then that is unlikely to be the problem. If anyone is changing constants without making a record of the changes, then they need to be educated.)

 

Your statement of the problem is too vague to be of any useful information. First the term "Full Speed No Load" is used with power generation applications. For mechanical drive applications, when the HP shaft reaches 14HS speed (typically over 80%), the startup sequence is completed (provided other conditions are satisfied). If the sequence is not completed in a specified period (depending on the type of starting device), the unit will trip on incomplete sequence or give alarm to that effect.

Please try to give as much information as possible. This will include, but not be limited to, the following:

1. Control system - Mark IV, Mark V, Mark VI etc.
2. What is the type of fuel?
3. What is the vintage of the unit? A, B,C, D etc.
4. Is it stand alone or in a parallel network of compressors?

Upon getting your answers, we can proceed.

 

I would suggest an operations point of view to be initially looked at!

If your earlier startups were successful, just the check and compare the "Wobbe Index" or the calorific value of the fuel used before and now.

This is because of a reason that during startup there is a maximum allowable GCV opening (startup FSR) within which the turbine should reach full speed no load.