We have a total ratchet failure after shutting down the GT, Frame 6 with a torque converter manufactured by Twin Disc. After 48 hours we are able to ratchet but after cranking using the diesel engine. We have replaced the self sequencing block, oil filter and relief valve but no success. Pressure on the ratchet mechanism cylinder builds to 800 psi.

Please advise.
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The pressure you are listing seems low, but that's just a guess. There usually isn't a pressure gauge on the system as provided by the OES, so do you know if the pressure is higher or lower than before this problem started?

If the Hyd. Ratchet Pump is driven by a D.C. Motor, have you checked the speed of the motor and the condition of the commutator brushes?

Some units now use Aux. Hyd. Pump pressure for the Hyd. Ratchet instead of a D.C. Hyd. Ratchet Pump. I'm presuming you have a D.C Hyd. Ratchet Pump for the purposes of this discussion. If your system uses Aux. Hyd. Pump pressure for the Hyd. Ratchet, then I would suspect some problem in the tubing between the systems.

Is the jaw clutch engaged? If so, then I would say the next thing to replace would be the Hyd. Ratchet Pump--presuming you've verified the pump speed is correct and the commutator brushes are good.

Most systems with a hydraulic ratchet and a jaw clutch have a manual valve (VM1-1, I think it's called on the Starting Means Piping Schematic drawing and in the Device Summary) that can be used to disable the clutch. I don't remember and I don't have any Frame 6 Piping Schematics to look at, but if the valve is in the wrong position it might reduce the pressure and not allow the ratchet to work correctly in addition to preventing the jaw clutch from engaging.

The valve is usually in a place that the handle can easily be kicked when crawling around the unit, and usually it's very dirty around the valve (good housekeeping is critical all around the unit and the control system!).

You say you've replaced the self-sequencer, filter and relief valve. And, usually most of the tubing is exterior to the L.O. tank so if there was a leak it should be readily apparent. Presuming the pump motor is operating at the right speed and the brushes are okay, the pump itself could be the problem.

The only other thing I could think of would be that the suction of the Hyd. Ratchet Pump might be plugged. Again, I don't have a Frame 6 Starting means Piping Schematic to look at, so I don't know where the suction of the Hyd. Ratchet Pump is or if it's supplied by the L.O. pump discharge header.

I have to presume that all the sequencing is working correctly, that the 33HR-1 limit switch is properly connected. Is L33HRF changing state?

Did this start happening after some maintenance outage?

 

If you measure downstream the pump about 800PSI (55barg), it appears to be normal operating pressure. Usually the ratchet pressure for GE FR5 and FR6 (included the FR5002) is about 50 to 65 barg (725 to 942 psi). Ensure that, the relief valve setting is about 103barg (1494psi) and you dont see this pressure during ratcheting.

Check also the 20CS solenoid and associated feedbacks such as 33CS and 33HR (check L33HRF). If the clutch is engaged and you ratchet pressure is maintaining 800psi during the cycle, the system is healthy. Most likely problem is the 33HR micro switch. Did you replace this already?

Good Luck

 

The pressure was established after a gauge was fitted on top of one of the ratchet cylinders. We have two Gas turbine Frame 6, so we compared it with the other good one which was operating at about 650 to 700 psi.

We removed the faulty ratchet one way clutch and fitted it on the working Gas turbine.It worked for about an hour and then failed to ratchet. We suspect the one way ratchet clutch could be the problem because it failed to ratchet on another turbine. Please comment.

The D.C. Motor, is functioning properly.

The jaw clutch is engaging properly and the manual valve VM1-1, is also functioning normally.

All the sequencing is working correctly, the 33HR-1 limit switch is properly connected and the L33HRF is changing.

This problem has been there for sometime but it was solved by replacing the sequencing block, filter and the switch. But this failure started happening after a maintenance outage.

 

It is not clear what type of clutch you have but, I assume that is the so called "jaw" clutch which is being actuated by two small cylinders. Are you mentioning these? So sometimes these actuators leaks and is not able to keep the clutch in engaged position. If you want to share the ratchet PID, I might able to help you out. Alternatively you may send a picture of your clutch system.
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Good Luck

 

We almost have the same problem here in our Frame 5. We initially found that racheting is not working and ratchet touble alarm appeared on the Mark VI HMI. Electrical replaced the breaker for HR pump and after starting the system we checked the field. We found that the clutch jaw is engaging but it is not moving forward. We thought that the 33CS is not actuating, but since the jaw is not fully engaged the limit switch will not actuate. We tried to bypass the switch momentarily to check if the sequence will continue and it did not.

We decided to do the following: We replaced the Self Sequencing Block and relief valve. The inlet filter to the block was also checked and found OK. We also installed a pressure gauge inlet to the block. After completing the replacement, we restarted again the ratcheting and found the pressure at around 65 BG, clutch engaging, 33CS actuating but the clutch did not move forward again and the 33HR limit switch (this is new with the block) also did not actuate.

I hope you can give us some suggestion on what other things we can check to solve this problem.

 

To understand the root cause of the failure, please follow the steps below:

1) The solenoid 20CS is functioning properly?
Ensure that the power supply is consistent and the valve is actuating? If the 20 CS is functioning properly, the feedback signal 33CS should set to logic "1" (L33CS=1).

2) If 33CS signal is "0" that means most likely the jaw clutch is NOT fully engaged.

3) Did you physically checked the jaw clutch it self for any mechanical failure? If not, remove the cover above the clutch and verify the jaw clutch position and the two small cylinders (actuators) which is pulling the clutch to the shaft at the gearbox side.

It appears that your ratchet pressure is within the operating limits. Most likely the two actuators are the bad actors.

Good Luck

 

The clutch type is "jaw" which is being actuated by two small cylinders which are functioning well and there are no leaks.
We have the ratchet PID. I will post a picture of the system for reference.

Thanks for your assistance.

 

In our case we found out that the problem was the "One way ratchet clutch" which is actuated by the self sequencing block.

When the diesel engine is running the "one way ratchet" is free but when in ratcheting mode it turns the shaft through the torque converter.

We dismantled the one way clutch ratchet and found that the inner casing and pin bearings were worn out.
To prove this was the problem we removed a good clutch from our Gas Turbine no.2 and fitted the faulty one and it failed to ratchet.
When we tested the good clutch on Gas Turbine no.1 it worked perfectly.

 

Thanks for the feedback! It's the most important contribution here at control.com!(c)

 

Please replace u r check valve. Sometimes check valve also giving problem to a pressure. Check valve near with forward stroke

 

In our case we found out that the problem was the "One way ratchet clutch" which is actuated by the self sequencing block.

When the diesel engine is running the "one way ratchet" is free but when in ratcheting mode it turns the shaft through the torque converter.

We dismantled the one way clutch ratchet and found that the inner casing and pin bearings were worn out.
To prove this was the problem we removed a good clutch from our Gas Turbine no.2 and fitted the faulty one and it failed to ratchet.
When we tested the good clutch on Gas Turbine no.1 it worked perfectly.

Hi Gunga,

Can you please post the pictures of dismantled ratchet mechanism & one way clutch arrangement.
As we are facing the ratchet issues, it will be helpful to troubleshoot.

Thanks