Trouble with the GCV

Hi,

Before I send this message, I will search more on control.com site to find any response about my request. But...

My problem is:

On Gas Turbine LM2500, when we start the engine it os OK until end of sequence. But after when we want to up the speed of TNH the FSR increases until 100% but the position of the valve stopped at 40%. On site there is the valve actuated by actuator controled by the servovalve MOOG 771K202.

When the engine is stopped and we do a calibration for GCV, the test is good. The position of valve respond for any FSR. Then for FSR 0-100% the position of GCV is 0-100%.

But when the engine is running, the position of GVD stopped at 40% for 100% FSR.

Who can guide me what to change or when to search the solution or what operation on MARK V to use and to see?

Thanks for you.

List *ALL* the process *AND* Diagnostic Alarms annunciated when the unit is running and the GCV is limited.

List the value of Control Constant FSKMAX.

From the FSR Display, what is the value of FSRMAN?

Is the unit on duel-duel?

Hi,Radhakrishnan and CSA,
The unit is only gas fuel.

and the parameters required by CSA are:

No Diagnostic Alarms annunciated when the unit is running and the GCV is limited.

There is no FSKMAX:

From the FSR Display, the value of FSRMAN is 100%
Thanks

I not sure I fully understand your request.

Are you attempting to speed up the turbine with the breaker open or closed.

Start up, acceleration, speed, or temperature control is probably controlling the position of the GCV. The minimum value gate is designed to ensure this.
Regardless of where one places manual FSR the value gate will override unless other procedures are followed or manual FSR is less than other values entering the value gate.

CTTech,

This aeroderivative turbine has multiple shafts, and to load the unit the HP shaft (which drives the axial compressor) will increase speed as the unit is loaded.

I was thinking the problem was that Manual FSR was stuck at 40%, but apparently that's not the case. I was also thinking someone had misadjusted the Maximum FSR setpoint (which is usually Control Constant FSKMAX) which was limiting FSR. (I've never seen a gas turbine which didn't have FSKMAX, but then I learn something new every day and I try to avoid aeroderivative turbines whenever I can.)

I was also hoping that by looking at the FSR Display the originator would tell us which value was also at 40% (equal to FSR) and that might be a clue as to what might be holding FSR back. No luck there either.

We asked for what alarms (both Process and Diagnostic) Alarms were annunciated when this was occurring, and we only were told that no Diagnostic Alarms were annunciated. I was wondering if there was some kind of "hold" which was active and annunciated with a Process Alarm might be present (don't you just love it when software programmers use Process Alarms to indicate operating conditions or normal conditions such as pumps running when they should, but don't alarm when that same pump isn't running when it should be?). Maybe some kind of load limit or hold. But no luck there either.

I think Damene is on his own here. We just don't have enough information and nothing we've asked for seems to have sparked some troubleshooting. I think there's no problem with the GCV or the servo-valve since it works fine when stroked manually, so something in the CSP seems to be limiting the FSR.

Thanks.

Just more information: our GT is a PGT25.
LM2500 is Gas Generator.
PGT25 is Power Turbine
PCL 602 is Compressor of load are.

We do not use a Generator then no breaker.

During start up, acceleration, speed, or
temperature control all parameters are normal but just after the end of sequence and we want to increase the THN speed, the position of GCV stopped at 40% and the signal command of FSR increases continually until 100%.

Thanks. Ready for other information.

Hi,

At the moment when I read your response I called to my collegue near the HMI of the engine.

I asked him for a bit of information about the GT parameters and his response is:

TNH = 86.34%
TNL = 73%
FSR = 40%
FSR_ Control = LP
GCV = 37%

And on FSR Display:
FSR : 54% color GREEN
Startup : 100.2% color bleu
Acceler : 77% color bleu
Speed : 128% color bleu
Temp : 100% color bleu
Manuel : 100% color bleu

After a few mins. maybe the operator can try to increase the speed manually.

The values on FSR CHANGES AS
FSR : 100% color GREEN
Startup : 100.2% color bleu
Acceler : 77% color bleu
Speed : 128% color bleu
Temp : 100% color bleu
Manuel : 100% color GREEN

I asked him if there are any alarms (both Process and Diagnostic). NO ALARMS.

Only during startup: excess of fuel gas

AND THE POSITION OF GCV STILL AT 37%.
Thanks for your help.

What is the GCV servo current (usually signal name FAG) when the FSR is at 100% and the GCV LVDTs indicate 37%?

What is the P2 pressure reference (usually signal name FPRG)? What is the P2 pressure (usually signal name FPG2)?

Is the unit load what you would expect it would be when the GCV is at 37%? In other words, is the unit output less than normal?

What happened to TNL when FSR went to 100% and FSG stayed at 37%?

Has anyone physically looked at the valve to see what the position is (not just what the LVDT says it is)?

As I recall, gas generators have their own speed control mechanism via the VSVs which are driven by the accessory gear box (or was that LM500s/LM6000s???). The HP speed is going to be whatever it needs to be for the load. If you've recently had some work done on the GG then I'd suggest you check with the people who calibrated the VSVs. Also, I think there's some kind of temperature sensor involved in the GG speed control mechanism.

If the load is as expected even if the GG speed isn't and the GCV position isn't, then there must be something else going on. When was the last time the P2 pressure transducer(s) were calibrated? Has the P2 pressure feedback been compared to a gauge reading?

Is there some kind of load limit from the compressor which is active?

I concur with CSA. FSR is being clamped. It could be compressor pressure ratio and a multitude of other parameters.

Find your FSR big block (possible named FSRV2)in your CSP. Open that rung in your dynamic rung display utility and find out what is clamping your FSR.

Don't know what kind of GCV you have, but I had a similar problem with a FS5002.

Turned out the actuator was passing due to a very small score on the inside of the cylinder about 40% of the way up.

However I had the same problem at calibration.

Possibly higher temperature of the oil when unit is running is changing the viscosity to allow it to pass.

Try and heat your oil to normal running temperature and try a calibration

Thanks.