In my plant after take shutdown of gas turbine frame 6B, ratcheting clutch disengaged after 45 minutes of cool down cycle.later we stop and start cool down,but clutch not engaged.hydraulic pressure build up by 88HR up to 90kg,but ratcheting not happens.please suggest me for respective reason

 

Every GE-design heavy duty gas turbine is supplied with a set of drawings usually referred to as P&IDs (Piping & Instrumentation Diagrams). GE has, for decades, labeled them as Schematic Piping Diagrams, or Piping Schematics. One of the set outlines the starting means and ratchet mechanism components. Have you used the Starting Means drawing to find each of the components to ensure they are all working properly? Specificially, there is usually a manual hand valve which can be used to engage or disengage the jaw clutch (if it is the toothed type jaw clutch), and it can sometimes be bumped or vibrate into the position that prevents engagement of the jaw clutch during normal operation.

There is also a Hydraulic Ratchet Jog Pushbutton located in the Accessory Compartment which can be used to ratchet the unit. Have you tried using the Hydraulic Ratchet Jog Pushbutton--and if so, what were the results?

The normal sequence of events for an automatic ratchet sequence is for the mechanism to move through a forward stroke (usually takes 15-30 seconds or so, and it usually "pulses" a little while moving. At that point the jaw clutch stops moving and the self-sequencer moves into a retraction stroke which readies the ratchet mechanism for another forward stroke. Limit switch 33HRF switches to a logic "1" at the completion of the forward stroke and remains a logic "1" for the duration of the retraction stroke, and switches back to a logic "0" when beginning another forward stroke. The ratchet mechanism begins a forward stroke and then stops; this is to ensure the jaw clutch teeth stay engaged during the 3 minutes before the next sequence begins.

But, all of this requires the jaw clutch to be engaged--which requires the manual hand valve controlling the flow of hydraulic oil to the rams which engage the jaw clutch to be working.

There is also the hydraulic ratchet self-sequencer which has been known to fail, and there is a solenoid, 20HR-1, which has also been known to fail. But, you need to use the Starting Means drawing and find and investigate all of the components to see if they are working properly. The DC Hydraulic Ratchet Pump motor also has brushes, which must be replaced from time to time (but almost never are--checked or replaced). AND, there is usually at least one, sometimes two, filters in the hydraulic ratchet tubing system which are rarely replaced, and can rupture internally and cause dirt and debris to contaminate the self-sequencer and the ratchet mechanism.

Those are the most likely causes of problems. Some ratchet mechanisms have had failed bearings and piston seals, also, but they are usually pretty robust devices and as long as filters are changed regularly they can last decades.

Best of luck. Please write back to let us know what you find and how you resolve the problem. Use the drawings and available means (including the jog pushbutton) to test the components, and don't forget to check the manual handvalve controlling the flow to the rams which engage the jaw clutch. NOTE that there are VERY STRONG springs on the jaw clutch engagement mechanism, so exercise caution when working on the jaw clutch!

 

samba.auce,

I neglected to mention that a common issue with jaw clutches is that the teeth get flattened (usually from forcing a "flying re-start" which does not allow the unit to reach zero speed before attempting another start) and won't stay engaged. If you watch the ratchet sequence, as was said, it usually "pulses" slightly which means when the forward ratchet stroke stops the turbine side of the jaw clutch usually spins just a small amount more which can cause the jaw clutch teeth to disengage and the springs on the rams to open the jaw clutch.

If you must be able to attempt a re-start without waiting for the shaft to reach zero speed, please--get a SSS (Shifting, Self-Synchronizing) clutch to replace the jaw clutch. SSS clutches are very robust and are essential for flying re-starts without damaging the starting means. They also use a non-contact type limit switch in place of the mechanical switch used for 33HR-1. They have a lot of advantages--not the least of which is being able to re-start without waiting for the unit to reach zero speed.

You can remove the cover of the jaw clutch and take a clear photo of the teeth, or, better, a short video, and post it to the thread. That's a very good way for people to see what's happening and make any comments or suggestions.

Hope this helps!

 

samba.auce,

I neglected to mention that a common issue with jaw clutches is that the teeth get flattened (usually from forcing a "flying re-start" which does not allow the unit to reach zero speed before attempting another start) and won't stay engaged. If you watch the ratchet sequence, as was said, it usually "pulses" slightly which means when the forward ratchet stroke stops the turbine side of the jaw clutch usually spins just a small amount more which can cause the jaw clutch teeth to disengage and the springs on the rams to open the jaw clutch.

If you must be able to attempt a re-start without waiting for the shaft to reach zero speed, please--get a SSS (Shifting, Self-Synchronizing) clutch to replace the jaw clutch. SSS clutches are very robust and are essential for flying re-starts without damaging the starting means. They also use a non-contact type limit switch in place of the mechanical switch used for 33HR-1. They have a lot of advantages--not the least of which is being able to re-start without waiting for the unit to reach zero speed.

You can remove the cover of the jaw clutch and take a clear photo of the teeth, or, better, a short video, and post it to the thread. That's a very good way for people to see what's happening and make any comments or suggestions.

Hope this helps!

We are trying manual jogging every time but rotor not rotates.two days gone.still we have same problem.finally we are waiting for BHEL team.

 

Thank you for the feedback.

No mention of the position the manual valve was found in. No mention of whether or not the jaw clutch halves are closed.

Two days wasted. You must not really want to find the problem.