We operate Ge frame 9e GT. I want to know when the clutch of the main fuel pump disengages when firing on Gas. does the shaft of the main fuel pump rotates when unit is selected on Gas fuel mode and on turning gear?

We tried to fire and as soon as it fires it trips because both the SRV and the GCV closes.

please what advice will you give me

 

kwaku,

The high-pressure liquid fuel pump clutch should be de-energized any time the unit has successfully transferred from liquid fuel to gas fuel and the unit is operating on 100% gas fuel. This goes for starting the unit with gas fuel selected--the clutch should be de-energized.

Now, having said that, the clearances between the liquid fuel pump clutch plates are very, very small (mm). Sometimes the plates contact each other when the clutch coil is not energized and transmit some torque (usually a very small amount) to the shaft of the high-pressure liquid fuel pump, causing it to rotate slowly. However, the liquid fuel bypass valve should be in the 100% bypass position (full open) so any liquid fuel that is "pumped" should be immediately recirculated back to the suction side of the pump--and there should be NO flow through the liquid fuel flow divider. The liquid fuel check valves usually have a cracking pressure of about 7 barg (around 100 psig) and with the liquid fuel bypass valve fully open there should be little or no pressure developed by the pump if it spinning slowly--so there should be no flow through the liquid fuel flow divider.

I venture to say that if you used a length of a piece of wood against the coupling between the output shaft of the fuel pump clutch and the input shaft of the high-pressure liquid fuel pump you could stop the shaft from rotating--unless the clutch plates were fused together (which has happened!). In this case, a high-pressure liquid fuel pump rotating at speed for a long period of time with only a small amount of liquid fuel recirculating through the pump through the liquid fuel bypass valve would get hot pretty quickly, and eventually damage the pump.

Any time a GE-design heavy duty gas turbine trips there is an alarm message to indicate precisely what the cause of the trip was. <b>ANY time.</b> What alarms are annunciated when the turbine trips? It shouldn't be because the liquid fuel pump shaft is rotating slowly

Use the Trip History display to determine when L4 goes from a logic "1" to a logic "0"--that is the time the trip was detected and the SRV told to close. Then, look at the alarms which were annunciated around that time and you can tell which alarm indicates the cause of the trip. (Sometimes, several alarms may be generated at the same instant in time; this can be a little difficult to decipher, but if you will list the alarms and the times of the alarms as they occurred, we can help you to determine what the cause of the trip was.)