i have a problem in GE MS6001B turbine.

problem description:
during start up ,the unit goes into temperature control mode at 35% speed and turbine stuck after that at speed 41%.

1- 5 of 13 exhaust thermocouples read between 590 and 613 C

2- FSR = 17%

3- FSR temperature reference = 547 C

4- CPD = 0.29 bar

5- torque converter pressure = 100 PSI

6- diesel engine speed (starting motor) = 1300 rpm

7- IGV angel = 43 degree

8- IGV type: non modulating open- close type

9- turbine control: Mark V

10- inlet fuel pressure before the stop valve: 5.2 bar

please advise

 

ahmed,

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This topic has been covered, and covered, and covered, and covered, and covered--and covered--on control.com.

When the fuel has to be increased to assist with acceleration BEFORE the clutch disengages then there is simply not enough torque being developed by the starting means or transmitted by the torque converter. The turbine, by itself (through the combustion of fuel to develop hot combustion gases to expand in the turbine section) simply cannot develop enough torque to accelerate itself below approximately 50-60% of rated speed. So, the starting means is used to provide a torque assist until such time as the turbine half of the clutch over-runs the starting means half of the clutch, the clutch disengages, and the turbine is said to be "self-sustaining" at that point, capable of deriving sufficient torque from the expansion of hot combustion gases in the turbine section to continue accelerating the turbine to rated speed.

You didn't say what the diesel speed was before this problem started (they're not all the same--similar, but not exactly the same).

You didn't say what the torque converter pressure was before this problem started (they're not all the same--similar, but not exactly the same).

You didn't say if the turbine had just gone through some kind of maintenance outage before this problem started, if the torque converter has been refurbished or replaced, or if there is a solenoid in the torque converter circuit if it is working correctly (usually labeled 20TU-1, or something similar--though not every GE-design Frame 6B heavy duty gas turbine has a solenoid in the torque converter circuit, some do--and they do get dirty and fail).

You didn't say how long it's been since the diesel was refurbished (they do need refurbishing--they take a great deal of abuse in starting GE-design heavy duty gas turbines). A lot of time when this happens it's after the diesel has been serviced or refurbished and the solenoids haven't been properly adjusted by the company performing the service. Also, dirty air filters can make it difficult for the diesel to get sufficient air to develop sufficient speed/torque. Dirty fuel filters can also cause a a problem with insufficient fuel getting to the injectors. If the diesel exhaust is white, there is a problem with one or more cylinders suffering from incomplete combustion (bad rings; dribbling injectors; bad valves; cracked piston; etc.). If the diesel exhaust is dark black--darker than usual--then the diesel is overloaded, usually caused when it can't get to rated speed.

Plain and simple: There isn't sufficient torque coming from the starting means through the torque converter. Your job is to determine why the Speedtronic is trying to put so much fuel into the turbine that it's prematurely hitting exhaust temperature control--and that's simply because there isn't sufficient torque from the starting means/torque converter. Plain and simple. There are several possibilities for why there isn't insufficient torque--but that's the cause. Use a logical troubleshooting progression and you will find the cause.

And when you do, please write back to let us know what you find and how you resolved the problem.

Finally, though it's not very likely--but still a possiblity, nonetheless--is that it sounds like the unit is burning liquid fuel. If that's the case, then it might be that the fuel nozzles of one or more combustors are plugged, or that the liquid fuel check valves of one or more combustors have failed. If there is a lot of white smoke coming from the gas turbine exhaust--more than usual during a liquid fuel start--then it could be a fuel nozzle/liquid fuel check valve problem. If the unit is dual fuel (natural gas/distillate), then one or more purge air check valves could be leaking liquid fuel--that would be obvious by checking the Tell-tale Leakoff (see the Liquid Fuel and/or the Fuel Purge P&ID(s)). You can use the manual selector valve at the discharge of the Liquid Fuel Flow Divider to check the fuel pressures to the individual combustors. Any which are much higher or much lower than the others are suspect (the nozzles and/or the check valves). The "rule" is that all fuel nozzle pressures should be within 10% of each other, so any outliers, again, are suspect. This can help to isolate the problem to a combustor (nozzle, or liquid fuel check valves, or liquid fuel purge check valve).

And, it could even be a combination of problems--particularly if it's been a long time since the diesel, torque converter and turbine have been serviced. If the distillate fuel supplier has changed recently, it could also just be dirty fuel.

Again, please write back to let us know what you find and how you resolve the problem. You could also try searching control.com for related threads, but they're all going to say the same thing--insufficient torque, or, in the case of liquid fuel, plugged nozzles or failed check valves.