Dear CSA,

We are operating two GE9E.03 units by Distillate and light crude oil (Main fuel), MARK VIe. Recently we noticed that the main fuel pump is engaged (when checked locally it is rotating) at Turning Gear in one unit while the same pump of another unit is disengaged. We want to determine which case is normal. And when does this pump engage?

 

In years past, the high-pressure fuel pump was driven by an output shaft of the Accessory Gear Box, and there was an electric clutch mechanism that would be energized to squeeze the clutch pack together to transmite torque from the Access. Gear Box output shaft to the input shaft of the high-pressure liquid fuel pump. USUALLY, the electric fuel pump clutch was only energized when the Master Protective Relay (L4) was energized (a logic "1") AND when liquid fuel was being called for (so after the purge timer was expired and the unit was ready to ignite flame in the combustors).

The high-pressure liquid fuel pump is usually a screw-type positive displacement pump--and it needs liquid fuel for internal lubrication. Using a liquid fuel bypass valve kind of provides a little safety here, but eventually that fuel is probably going to get very hot being recirculated.

There should be a solenoid output of the Mark VIe to energize the electric fuel pump clutch. I believe the output signal name was something like L20CF1X (or it might be all lower-case--or should be), but it should NOT be energized unless the L4 Master Protective Relay is energized AND liquid fuel is being called for (after the purge time is complete and the unit is ready to establish flame in the combustors).

HOWEVER, GE Belfort has a well-known habit of changing decades-old, established and proven logic (why? because they can!). So, you need to check the application code in the Mark VIe, the Liquid Fuel P&ID (to see if there's a clutch on the input to the high pressure liquid fuel pump, and the Device Summary to see what the clutch device number is.

Best of luck. Please let us know what you find!

 

Yep, there’s an electric fuel pump clutch, 20CF-1. Typically, that should not be engaged while on turning gear (Cooldown). Check to make sure the Mark *VIe solenoid output that drives the electric fuel pump clutch while on turning gear, and if it is determine why it is and resolve the issue.
The electric fuel pump clutch plates are very close to each other, and sometimes they all turn together when they shouldn’t. Suggest selecting COOLDOWN OFF (when possible), removing the coupling cover between the high pressure fuel pump and the electric fuel pump clutch output shaft and trying to rotate the coupling by hand (DO NOT FORCE IT!). It should rotate easily, and if it doesn’t it could be that the plates here welded together or something else is mechanically wrong. If it seems to be difficult to turn it could still indicate a problem with the clutch.

If the coupling rotated easily by hand, with the coupling cover still removed force the Mark* VIe electric fuel pump clutch solenoid to a logic “1” and then try to rotate the coupling by hand. It should not be possible to rotate the coupling by hand. Be sure to unforce the output when finished (it should automatically return to a logic “0”).

i don’t know what turning gear speed is or what the site Danger Ranger would say about putting the unit by hand on Cooldown and after ensuring the Mark* VIe electric fuel pump clutch output is not energized trying to stop the coupling from rotating WHILE WEARING GOOD, HEAVY LEATHER GLOVES. It shouldn’t take too much force to stop the coupling from rotating; it it does it’s probably another indication there’s something wrong with the clutch.

It is VERY difficult to hear the electric fuel pump clutch engaging when it is energized. You should make sure the solenoid output is properly switching 125 VDC to the electric fuel pump clutch. The solenoid output contacts may also be welded closed.

It’s a simple system, as you will find as you start getting into it during troubleshooting.

As before,please write back to let us know how you progress with resolving the issue.

 

Yep, there’s an electric fuel pump clutch, 20CF-1. Typically, that should not be engaged while on turning gear (Cooldown). Check to make sure the Mark *VIe solenoid output that drives the electric fuel pump clutch while on turning gear, and if it is determine why it is and resolve the issue.
The electric fuel pump clutch plates are very close to each other, and sometimes they all turn together when they shouldn’t. Suggest selecting COOLDOWN OFF (when possible), removing the coupling cover between the high pressure fuel pump and the electric fuel pump clutch output shaft and trying to rotate the coupling by hand (DO NOT FORCE IT!). It should rotate easily, and if it doesn’t it could be that the plates here welded together or something else is mechanically wrong. If it seems to be difficult to turn it could still indicate a problem with the clutch.

If the coupling rotated easily by hand, with the coupling cover still removed force the Mark* VIe electric fuel pump clutch solenoid to a logic “1” and then try to rotate the coupling by hand. It should not be possible to rotate the coupling by hand. Be sure to unforce the output when finished (it should automatically return to a logic “0”).

i don’t know what turning gear speed is or what the site Danger Ranger would say about putting the unit by hand on Cooldown and after ensuring the Mark* VIe electric fuel pump clutch output is not energized trying to stop the coupling from rotating WHILE WEARING GOOD, HEAVY LEATHER GLOVES. It shouldn’t take too much force to stop the coupling from rotating; it it does it’s probably another indication there’s something wrong with the clutch.

It is VERY difficult to hear the electric fuel pump clutch engaging when it is energized. You should make sure the solenoid output is properly switching 125 VDC to the electric fuel pump clutch. The solenoid output contacts may also be welded closed.

It’s a simple system, as you will find as you start getting into it during troubleshooting.

As before, please write back to let us know how you progress with resolving the issue.

Dear WTF,
Thanks a lot for your quick reply about GT liquid fuel pump engagement.
for your information nowadays the unit is running, and we are going to shut it down in two days coming.
Then we will do all required checking and will write back to let you know about the issue.
Regards.