rotation speed 1

[facetoface]

We have got gas turbine model GT10B-Alstom and this turbine is double shaft (HP turbine and low pressure turbine)the HP turbine speed is variable and power turbine speed is constant as 77300 and reduucedto 1500 rpm to generator speed
The generator shaft is drived from both side steam turbine side and GT side through SSS clutch, when GT is stopped and ST is runnibg there are small speed 89 rpm at power turbine of GT where SSS clutch disengaged from GT side
Please, from where speed comming and is this problem and if yes how can solve

 

[rmw]

Does your GT have a turning gear or similar device that rotates it while it is off in order to keep it from bowing?

rmw

 

[settar]

GTs are equipped with barring or turning gear devices in order to avoid rotor distortion after gt is shut down. The turning gear engages at a predetermined rotational speed and rotates the shaft at a constant low rpm until the turbine metal temperature falls to a certain temperature at which rotor will not bow. I suppose your GT rotor turning comes from this barring system. It should automatically stop or your control system should give permission to stop turning gear operation after rotor is adequately cooled down.

 

[facetoface]

GT have barring after 8hr the barring stopped , but this case only comming when the generator is drived from ST side for all time ,may be this rotation from generator shaft but how SSS clutch is disengaged

 

[rmw]

Since you have ruled out the barring, is there something possibly dragging in the clutch. If so, I would expect it to heat up somewhat due to the friction.

Also, I assume that your clutch is between the reduction gear and the generator. I think there is a typographical mistake in your power turbine operating speed please clarify. Is the 89 rpm you are giving us the rotational speed of the gear shaft at the clutch, or the turbine rotor speed?

What, by the way is the rotational speed of the turbine rotor(s) during barring?

rmw

 

[facetoface]

This turbine double shaft there is no mechanical connection between HP and LP turbine , so power turbine speed is reduced via reduction speed then connect via SSS clutch to generator(double end drive 1500rpm) , so the mention speed is power turbine speed (LP turbine) ,when steam turbine is stopping there is no speed only this case when GT is off and ST is on

 

[turboco1]

It should only be a "problem" if you lose oil to the Power turbine bearings or reducing gearbox...there are marine applications where power turbines "free wheel" with the line shaft yet they have a shaft brake if necessary to stop it for maintenance. Yet, somehow I suspect that your SSS needs tweaking to get full disengagement when there is no drive torque applied from the GT. I would not want the gears and LP turbine always rolling at a cold condition and low speed.

 

[facetoface]

Thanks but what you mean
SSS needs tweaking

 

[facetoface]

I have not more information for the mention clutch, can you tell me how can I investigate or what the part for fully eisengamment

 

[rmw]

I still think there is an error in your turbine speed number that you gave in the original post and the post you did in the automotive forum. I questioned that before. While I know that is is probably quite a bit higher than the generator's 1500 rpm, 77K seems a bit much.

Is there any excessive noise coming from the clutch? (like you can hear anything out in the plant) Still, you can take a hollow tube and hold it near the clutch with the other end by your ear and hear if there are any unusual noises in the clutch.

I am beginning to suspect that the pawl is dragging due to the low centrifugal forces of 1500 rpm, and if so, then you should be able to hear the ratcheting noises if you can get a good "listen" on the clutch.

Then again, you may just have excessive oil or grease in the clutch that is acting like an automotive torque converter when the clutch is declutched. If this is the case, the oil should heat up after a while, and the clutch will indicate a high temperature.

If something is physically dragging in the clutch, it should have "lunched" itself by now and either galled or worn down sufficiently to have stopped dragging.

So, look for excessive heat or ratcheting noises.

rmw

 

[settar]

Can you clarify your ST configuration. You mentioned a GT, an HP turbine and an LP turbine. (When you say HP and LP, I refer to ST.) And I understand that you use process steam in ST.(no HRSG). Right?

 

[rmw]

I understood his use of HP and LP to refer to the two turbine shafts of his two shaft GT.

rmw

 

[turboco1]

By all accounts of his input to his own thread...he has a generator between a GT and ST. The GT is a 2 shaft GT which means it, the GT, has an HP section consisting of a compressor and hp turbine on one shaft, the hp turbine of the gt drives the compressor of the hp turbine section the same as a single shaft gt. The LP section of the GT is driven by the hot gases exiting the HP turbine...this LP turbine is AERODYNAMICALLY coupled to the HP turbine of the GT. This LP "power" turbine IS the drive turbine to the generator on the GT end of the generator. There is a reducing gear and SSS clutch between the GT LP "power" turbine and the generator. The SSS clutch is between the reducing gear and the generator. The SSS clucth is an "Over-Running" clutch design (ages old)... if the generator speed becomes higher than the LP power turbine speed it will disengage the GT-LP power turbine from the generator. The purpose is so the generator may be driven solely by the steam turbine on the other end...you stop the gas turbine and the SSS clutch sensing a decrease in drive torque from the GT Power Turbine, disengages the reduction gear/power turbine train and leaves the generator at reduced load with the steam turbine only. SSS and BLH clutches...I cannot remember for sure which one it is....but as I recall one of them or both are oil operated and speed sensitive, and there might be a pick-up tube which requires and adjustment in height. I believe for sure the BLH is oil operated but I cannot recall exactly the SSS clutch construction. In any event, no matter what GT rated speed is, when the GT is taken off-line, the SSS clutch should FULLY disengage. You should be able to cool the GT and go to "barring" operation and eventually standstill. The entire purpose of SSS and BLH clutch designs is to switch between primary drivers or share load.

 

[ScottyUK]

I think RMW is correct - aero-derivative turbines have coaxial shafts carrying a high speed turbine which has no direct coupling to the load and a low speed turbine coupled to the load. The LS turbine is driven by the HS turbine. I agree that the speed of the HS turbine sounds high, probably by a factor of ten or so.


----------------------------------

One day my ship will come in.
But with my luck, I'll be at the airport!

 

[turboco1]

"If the speed of the input shaft is reduced relative to the output shaft, the torque on the helical splines will reverse. This causes the sliding component to return to the disengaged position and the clutch will overrun." See the Link below.

http://www.sssclutch.com/marinepropulsion/index.htm?welcome.htm~mainFrame

us old navy guys are still doing it

It is the BLH that uses oil and a pick-up. I had a BLH on the Cummins propulsion shaft and a SSS on the Caterpillar propulsion shaft and an LM1500 in the middle. The BLH gave us headaches and the SSS never. But it sounds like his internally sliding helical splined coupler is hangin up and cannot fully disengage.

cheers

 

[turboco1]

The pawls should be fully out of action by centrifugal force. The pawls are located in a shielded circumferential channel and if you are not hearing a lot of munchin and crunchin going on and have no high temperatures in the clutch housing you are possibly seeing a hydrodynamic affect of the pawls acting on the sliding component and helical gear free wheeling the power turbine. Try a brake if you need the power turbine stopped...

 

[facetoface]

Okky, there are two SSS clutches for both sides of generators , my gus is this speed result from gnerator rotation that transfer the torq to PT via SSS clutch then to reduction gear by feadback , is this correct

 

[turboco1]

The actual rotation is being transferred via the SSS clutch.

The other SSS clutch is driving the generator when the steam turbine is online.

The output side of the SSS clutch between the generator and the PT is rotating at generator speed. This is causing the PT to spin. A hydrodynamic effect inside the Power Turbine SSS clutch is freewheeling your PT most likely.

 

[facetoface]

now , the SSS clutch is disengage between gearbox and generator frrom GT so the coubling between SSS clutch and gear box is not rotating with the same generator speed, I think with speed less than PT beacuse gear box in this case will increase(feadback) the speed , is this correct

 

[turboco1]

The rotation of the Output Hub rotation, (the generator shaft) is hydrodynamically rotating the Input Hub via the Sliding Helical Component...this is rotating the gears in the gearbox and is thus rotating the PT...the affect cannot be mechanically quantified by gear ratio calculations because the coupling in this case is not mechanical... it is hydraulic. The SSS clutch has oil inside it right, for lubrication of the helical gear component and ratchet teeth, etc...?? It is just and affect of not having a power turbine brake in my opinion.