Gas turbine model is 9fa with DLN 2.6

The GT tripped with alarm "Gas Aux. Stop Valve Position Fault." The GT was running at 152 MW at the time of trip.

Immediately after the trip, informed to I&C. I&C checked and found the solenoid of the Gas Auxiliary Stop Valve to be defective. The defective solenoid was replaced and function checks of auxiliary stop valve were carried out. After function checks, the unit was declared available and started.

Just 2 days back same incident happened on another Gas turbine (In our plant we have total 4 gas turbines). I&C replaced the defective solenoid and gave go ahead signal to start the unit. the same practice they have recommended for this latest tripped unit too.

What could be the possible reasons for defective solenoid..why its suddenly happening and causing the machine to trip on loss of flame.

The following alarms were received at DCS at the time of trip<pre>
02:46:45:479 Gas Aux. Stop Valve Position Fault
02:46:45:519 Gas Aux. Stop Valve Trouble
02:46:45:559 Automatic shutdown
02:46:46:759 Gas Supply Pressure Low Inhibit Raise
02:46:45:919 Gas Aux. Stop Valve Position Fault
02:46:46:919 Loss of Flame Trip.
02:46:46:919 Gas supply pressure below safe unloading limit
02:46:46:919 Master Protective Trip.
</pre>
Please share your experiences and possible suggestions to avoid re-occurrence of this events with other gas turbines.

Regards
Surya

 

Surya,

Has anyone checked with the solenoid coil manufacturer to see if it's suitable for the application on the Aux. Gas Stop Valve.

Be sure to explain all of the factors and circumstances. For example, is the gas fuel heated? Have you taken temperatures in the area of and of the solenoid coil?

Is the solenoid coil rated for continuous energized operation?

Is the solenoid coil located in direct sunlight?

Is the voltage being applied to the coil suitable for the application?

Is there a large voltage drop in the wiring between the turbine control panel and the Aux. Gas Stop Valve solenoid coil?

It's factors like this that need to be considered in the choice of a solenoid on the Aux. Gas Stop Valve actuator, and which should be discussed with the solenoid manufacturer.

Please write back to let us know what you find. And, if you can answer some of the questions above for the many people who read these posts it would be most helpful and much appreciated.