unable to start gas turbine

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Thread Starter

ahdash

Frame 5 mark II GT we still unable to start the machine, the firing is ok , burners 7 & 8 are ok but when it reaches (2600 rpm) speed it trips on loss of flame.

33CS limit switch found faulty and replaced by new one and the power supply 125volt to the clutch found loose, repaired

First 2 starts on diesel fuel, reached 2500 rpm then tripped without any indication

one start on gas, it reached 3000 rpm then tripped without any indication.

14HA was OK but 14HS not OK.

What you recommend, what could be the reason?

Thanks alot

<b>moderator's note:</b> this looks like a continuation of an earlier thread, but I could not find it.
 
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Bob Johnston

As it is MK II, this can be hard to diagnose.

1)Is the diesel still running when you trip (It should be). I'm just looking at the clutch limit switch problems that you had and wondered whether the diesel was shutting down early?

2) Getting 14HA is OK as it usually set around 50% speed, is it doing anything? You won't get 14HS to at least 95% speed.

3)What kind of flame detectors are you using? Is the flame signal healthy? Do you have sight glasses in your combustion cans?

4)Do you have any kind of recorder that you can hook up to the machine? Multi-channel pen chart recorder would be useful. You could look at VCE voltage, gas valves LVDT feedbacks, Speed, Trip Oil Pressure switches, 4s relay status.

I'm afraid on MKII it can be a slow process of elimination. Gather as many people around monitoring Panel Meters, Gauge Panel, Gas valves, Fuel gas pressures, etc.

Good Luck and report back your findings
 
R

Ronald Anderson

I have 27 years experience as a GE Gas Turbine Controls Specialist. I now work at Advanced Turbine Controls.

I'm also an expert on MKII Speedtronic Controls and was the lead Controls engineer for GE in the Southern Region for many years.

14HS is only active when you are at operating speed.

14HA is the 'acceleration speed control' actively controlling the unit's fuel.

Many many things can cause this..What were your temperature spreads on Gas and what where they on liquid?

What was CPD?

Also remember if the rate of acceleration is too slow the back end will heat up causing the temperature control circuits to bias fuel down to a point of flame out. In MKIV and later systems this parameter is FSRT. If in a MKII era control the startup fuel is speed control circuits, in digital systems it is FSRSR_SU.

Remember whether you talking VCE (MKI and II) or FSR (MKIV and later) calculation for fuel reference, it will always track the system calling for the least amount of fuel.

Excessively hot back end will call for low temperature control values and can go so low as to cause flame out. By the way, this scenario is not annuciated in a MKII system. You would only see the turbine during start up have a very slow acceleration or bogged start or hung start, which eventually results in a loss of flame trip.

I hope I've given you some things to think about and have helped in some small way. Good Luck!
 
R

Ronald Anderson Senior Turbine Controls

Also remember if you can't get the unit up to about 65% TNH or speed the mass flow will not be enough to cause larger Delta T temperature drops a cross the turbine stages, that is the only way to get the back end to drop temp significantly.

but i ramble.
 
One comment on 14HS setting in the following statement by Bob Johnston:

> 2) Getting 14HA is OK as it usually set around 50% speed, is it doing anything?
> You won't get 14HS to at least 95% speed.

The 95% setting is correct if the turbine is a 5001P. If it is a 5001R, the setting might be as low as 75% (I think) - in mechanical drive applications, the "R" could run down to 80% speed.
I didn't see anything to define which type of frame 5 this is.

Also, there were comments referring to compressor discharge pressure as "CPD" - in Mark II days it was called "PCD."
 
Yes you are right, the rate of Acceleration is too slow; the temperature reaches about 500C.

Is the VPR2 (REGULATING VALVE) can cause this trip if it remains open, as the hydraulic oil pressure does not go more than 1.4 bar (it should be 1.7 bar)

thanx
 
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Bob Johnston

I guess you are talking about the Lube Oil Pressure! You may as well adjust it and get it right and out of the troubleshooting zone, but I don't see that it would be a problem at 1.4 Bar
 
I would like to confirm about one thing???

While we are going to replace VPR2 we found a hole inside the new one (like an orifice). the same we found on the old one. Is this normal?

Please advice
Ahdash
 
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Bob Johnston

Are all your Start-up VCE settings as per the Control Spec.? It kind of looks like you are losing the machine on Acell. Control both on Gas & Liquid.

500 Deg. C is OK at around 2500 - 3000 rpm as long as no higher.
Are you staying on Start-up Control for most of the start-up (a little bit of Accel. Control occasionally is OK) but you don't want to be on Temperature Control. Check the Control Mode lamps on your panel and tell us what you see.
 
B
Yes, VPR2 has an internal orifice, it shows on the P&ID. VPR2 can never be allowed to completely close as it would close your L.O. supply
 
Hi dear

I would like to inform you that, we have started our machine and put online. thank you a lot for your cooperation and support.

the problem was on VPR2, replaced then everything ok

Yours faithfully
Ahdash
 
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