PM3 G3 + Purge Lockout DLN26+

Dear All,

Just need a clarification:

We have experienced an lockout on PM3 Purge line, after a problem of 71pg fault. We have passed to PPM Mode piloted premix (DLN2.6+) 9FB Machine.

The fault of 71PG of DLN was solved. I look into the logic, we have tried to change the combution mode. We get a load reject mode.
We have tried to resychro again. Its ok, but the lockout always exists.

Looking into the logic I found that only the reset for the lockout is the loss of flame! We could avoid that before 15min of condensate time. After the 15min we cannot reset the lockout, only as i said by loss of flame (risk condensate in the line PM3). could you please explain how could get condensation in the line PM3? Is the shutdown of the unit is the only solution? I mean without forcing anything (because the risk of condensation is existing.

Another question if really we have condensation whats the risk of damage on the machine if we force the logic?

Many thanks in advance.

>Another question if really we have condensation whats the
>risk of damage on the machine if we force the logic?

One quart of natural gas liquids (condensate) equates to approximately 10 MW of power. If that flows into a combustor or combustors the sudden ignition of that much fuel can cause loss of flame (because of the sudden ignition), combustion liner damage, and fuel nozzle damage. It's long hydrocarbon chains that cause flashbacks in DLN 2.x combustors, and those flashbacks have been known to result in damaged welds of fuel nozzles which led to other catastrophic problems.

You don't want any natural gas liquids (condensate) to get into the combustors.

Can you better describe how loss of flame is a reset for the lockout? That doesn't seem logical in the least, at first thought. If you can describe the logic better it might make a little more sense (though it's hard to see how without a much better understanding of the logic).
Dear CSA Thanks for the reply.
Lets talk logic now:

We have L99PGG3Z (15Minutes G3 Condensate time), its activated after 15min of:

1/ LPGG3_PFLT (G3 Manifold purge fault) AND L20PG3ON (Command to turn on G3 purge)
2/ L3PG3ON (Gas fuel purge G3 manifold permissive logic) AND L86PG_G3 (G3 Manifold purge lockout).

Then the L99PGG3Z Its Latched (in the same line of thd RUNG Bloc) with the L28FDY (TD Loss of flame). The same story as L86MR1, but they use L28FDY. I think GE preconise shutdown of the unit after 15 min of lockout of the purge (they sure we have a condensation).

Then you must shutdown your unit as I suggested to do and we did. Now we have started again and everything is ok. What do you think?.

>Lets talk logic now:

If only we could do that (talk logic) about GE Belfort "logic." It's not, so we can't. L99??? LPGG??? That's just unconscionable. And illogical. Why even have signal names when they are screwed up--just like it seems the "logic" is?

You need to go to the supplier of the turbine and get THEM to tell you what the heck they were thinking--'cause I can't. And, won't even try at this point. You're using GE-supplied Longnames (signal name descriptions) which can't be relied upon, especially when GE Belfort is involved. (GE Belfort was given the responsibility for the control and protection of Frame 9 machines--9Es, and 9Fs and 9Hs. And they have shown, and continue to show, a propensity for needlessly over-complicating things. AND, for using stupid, illogical signal names in the process.)

They are the best ones to justify and rationalize their logic. And, if it's wrong (which they'll NEVER admit!), they would be the best ones to fix it. Though it's likely they will add more complicated logic.)

Look, the truth is things like this happen because some unit somewhere experienced condensate--and that can be catastrophic. And if the unit was under warranty, it was probably paid for by GE. So, logic like this (well not as complicated and illogically written as this) makes it way into the code.

Best of luck. It would be very nice if you would write back when you get some justification/rationalization from the supplier. (It may have been BHEL or some other packager, but, ultimately, GE Belfort was "involved.")

Also operating a 9FB, we have never had condensation problems. We have had detection alarm level 71PG. We checked in the drainage of the level the non-existence of water and checked the failure in one of the level detectors of the 71PG.

The other cause of condensation is leakage in the heat exchanger.

>Of course look at this share:
>What do you think?

Thanks for the sharing and sorry for my delayed reply.

FYI: The DLN 2.6+ gas fuel purge system provides delivery of positive purge air coming from the axial compressor discharge to the gas
turbine fuel nozzles and piping. and all of this is needed for the following reasons:

1) Keep piping free from condensation.
2) Prevent back-flow of combustion gases into the nozzles.
3) Prevent cross-talk between fuel nozzles.

As i can see from the screenshot you had a problem with G3 purge line and as far as i understood it was caused by the L63PGG3LZ signal. (hope i am correct)?

comparing the logic i have on my screen is the same as yours, and as long as the 15 min has passed <i>oups!</i>. the lockout is activated, and no chance to get rid of it but by shutting down the machine (which means loss of flame). Or if you are aware of what you are doing and the problem is solved' you can take two seconds to force and unforce the signal (L99PGG3Z NOT L28FDY!!!).

I can see that the OEM is taking all precautions with this matter, avoiding the risk of having a condensation which may harm the combustion system severely.

I have attached the screenshot to the address you indicated. In block RUNG_90 it is the same. But the RUNG_89 block is different.

If the exit temperature of the scrubber gas is 185 ° C (365F), condensation is difficult to exist. The level 71 PG detector is for detecting leaks in the exchanger.