Hello all, we have 2 9E GT's with Mk4 Speedtronic. GT1 perfoms a fired shutdown on breaker opening all ok with flameout around 1000rpm, however, GT2 flames out almost immediately on breaker opening. Is there a constant or logic block somewhere that might have been tuned inadvertantly that is causing this? Thanks for any advise.

 

@cleverzippy,

If this is a recent/new problem, it suggests something has changed. That is the primary intent of all of the questions--to try to determine what has changed that might cause the problem. Although the questions about alarms (Process and Diagnostic) are not at the top of the list--they are probably the MOST IMPORTANT questions to answer (after, of course, which fuel do the machines burn).

1) WHAT FUEL ARE THE MACHINES BURNING WHEN THIS OCCURS?

2) Has anyone "calibrated" the fuel control valve LVDT feedback on the machine experiencing the problem?

3) When did this problem start? After a trip from load? After a maintenance outage? (If it was a maintenance outage, what was done during the maintenance outage?)

4) What Process Alarms are present on the two machines just prior to when a STOP is initiated?

5) What Diagnostic Alarms are present on the two machines just prior to when a STOP is initiated?

6) Is the fuel supply pressure stable during low load operation and when a STOP is initiated?

The typical Mark* IV turbine control system is a digital control system, meaning that it's very difficult to find a single Control Constant or logic block to have changed "all by it's self". We don't know if there are special control schemes to adjust a particular Control Constant or rung(s) that might be initiated by a contact input from another control system. Again, if everything has been working fine, no one has been mucking with the Mark* IV Control Constants or sequencing logic and there are no unusual Process- or Diagnostic Alarms the expectation is something has changed. If there are different Process- and/or Diagnostic Alarms on the two machines prior to shutting down or immediately after the generator breaker opens on the machine experiencing problems then they could help with understanding the problem(s) (it could be a combination of two or more issues).

The Mark* IV has a little "feature" that wasn't intended--while it does take two control processors to initiate a closure of the fuel shutoff valve it could be that one control processor senses low-low L.O. pressure and a second processor senses high-high L.O. temperature. The intent was that two of the three control processors would detect the SAME condition and initiate a trip, but if one of the three detects a trip condition the 4 relay for that processor will drop out, and if a different processor detects a trip condition its 4 relay will drop out--which will drop out the fuel solenoid valve and shut off fuel--with no Process Alarm to indicate why (except for the Loss of Flame Trip--which should be initiated under this scenario).

But--if one processor detects a trip condition and the other two don't, there WILL BE Diagnostic Alarms to alert a conscious operator to the condition (prior to the eventual trip).

Anyway, we need MUCH more data and answers to be of any further help!

 

@cleverzippy,

With regard to Question #2, I am NOT suggesting the fuel control valve LVDTs need calibration—just asking if someone “calibrated” the fuel control valve LVDTs prior to the start of the problem. (LVDT feedback rarely requires calibration (much less often than people believe!); that’s one of the main reasons they are used on aircraft and rockets, they are very reliable and NOT prone to drift. Improper calibration can cause knock-on problem(s).)

 

Hello all, we have 2 9E GT's with Mk4 Speedtronic. GT1 perfoms a fired shutdown on breaker opening all ok with flameout around 1000rpm, however, GT2 flames out almost immediately on breaker opening. Is there a constant or logic block somewhere that might have been tuned inadvertantly that is causing this? Thanks for any advise.

Review if any recent maintenance, upgrades, or configuration changes were performed on GT2. Misconfigured tuning parameters or new firmware could inadvertently affect performance.

 

@bidrohini,

I'm going to start calling you Gilligan, as you have the tendency to repeat what the Captain said which had the Captain looking directly into the film camera with a "What the hell?!?!!?!!" look (which is how I feel when I read some of your responses).

Occasionally the Captain would remove his captain's hat and slap Gilligan on the head--and Gilligan had no idea why the Captain did that.

In case you're wondering--I'm referring to an old American television show, Gilligan's Island. One of the classics of all time.

"...A three-hour tour; a three-hour tour..."