Gas Turbine Fail to make firing in Gas Fuel


Thread Starter


We have gas turbine frame 9EA. We can not start it by using gas fuel because it trips due to GAS LEAK TEST FAILED.

Please help me.
1-Have you checked gas train tightness control relay? Sometime it gets faulty or internals get contaminated so it fails to work. Check " DUNGS VPS-504 " literature on net for it's working.

2- You might have an actual leak somewhere. So better not to start befoe rectifying it !!
Posted by anasdiab on 17 July, 2007 - 4:14 pm
"We have Gas turbine from GE frame 9E. We tried to start it by using Liquid Fuel but it failed and Tripped on EXHAUST OVER TEMPERATURE TRIP.

This happened when turbine make firing, the exhaust v reaches 666 C and the trip set point is 627 C. The exhaust Thermocouples No 1-7 and No, 18-24 read this high value."

Is this the same turbine???

I thought this had been covered previously, but when I searched there had been no replies to the original post.

The OEM has some new sequencing which checks the SRV and GCV for leakage during start-up before firing and after shutdown. And, if the valves don't hold, then the gas leak test failed and the turbine is tripped, and when it's tripped after a shutdown it can't be started either.

As with any unfamiliar alarm, you need to work backwards through the sequencing logic, looking up the name of the logic signal which annunciates the alarm, then seeing what causes that logic to be picked up, until you understand what caused the alarm to be annunciated.

If you have a Mark VI, you use Toolbox, and using the Process Alarm's Drop Number, also called an Alarm ID, you click on View, Reports, Alarm List. Then you scroll down to the drop number or Alarm ID number and you write down the logic signal name near the left side of the display, something like L86GLTA, for example.

(You can also double-click on the signal name in most versions of Toolbox and it will take you to the pin of the logic signal name. You then have to click on Finder (the binocular icon on the toolbar at the top of the display), then click on the Signal/Variable Usage tab, then click on the line with the asterisk, then click on the GoToSelected Item icon, the middle icon in the upper right corner of the Finder window.)

Once you have the logic signal name, you click on Window, then select the .m6b file to return to the sequencing, click on the Finder icon (the binocular icon on the toolbar at the top of the display), then type g1\l86gtla (if L86GTLA is the signal name you wrote down, and this presumes this is for unit G1; change that also, if necessary). Then in the Method drop down, you want to click on Exact, then click on Find. You will then be presented with several lines in the window at the bottom of the Finder window, click on the line with the asterisk, then click on the GoToSelected Item icon (the middle of the three at the top of the Finder window). You should be taken to the function block diagram where the logic signal name is written to, and you can start working backwards from there.

If you're not copying the exact alarm test message, then it seems like the sequencing at your site is a little different than most. You will need to find out if the SRV or the GCV failed the leak test, or if the SRV failed to track the reference during the test.

Now, if this happened immediately after some maintenance outage, it's likely that some valves in the Gas Compartment might be out of position; maybe they weren't returned to their normal running position after a calibration check or maintenance procedure and the P2 pressure transducer(s) aren't sensing pressure? Or they're venting when they shouldn't be?

So, there's either a valve line-up problem (someone put something in the wrong position or forgot to put it in the right position), or there's a leak. The leak could be a tubing leak, a flange leak, or an actual valve leak; but you need to find out what's wrong and fix it.

But, you need to learn how to "read" the sequencing logic in your machine and when you encounter a Process Alarm which you don't immediately recognize, you need to work backwards from the Alarm Drop (or Alarm ID) number to see what caused the alarm to be annunciated.

It seemed to be that most people were responding to these kinds of requests when they resolved their issue in the past. Hopefully you'll let us know what you find and how you fix it; it seems only fair for the free advice!