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

 

[facetoface]

Thanks , but let us first to specify the reason ,now this rotation from SSS clutch due to not fully disengagement and this hydrodynamic rotation also comming due to sliding compents and that is not fully didengament at SSS clutch, please this is correct (I will be with you please)

 

[turboco1]

The clutch IS disengaged.
The oil inside the clutch in the channel area of the pawls is creating a windage type flow circumferentially around the ratchet teeth between the ratchet teeth and the pawls. It is acting like a Reaction Turbine... the oil is creating low pressure area on the face of ratchet teeth and creating a rotational force which is transmitting through the sliding component to the input shaft.

 

[facetoface]

thanks, I think you ar right but what can I do for you please

 

[facetoface]

what you means with windage type flow

 

[turboco1]

Windage is the affect of the rotating components inside creating a wind. On couplings of large turbine generators, many have the heads of the studs and the nuts covered with a "windage cover" to prevent them from creating a turbulent wind inside the coupling area. When windage exists in this case, it is rotational.
The close tolerance of clearance between the pawls and the ratchet teeth and the oil and both being enclosed axially by walls on both sides, prevents the ability of minimizing the low pressure area being developed...the ratchet rotates due to this low pressure being developed on the teeth engaging faces by this oily windage. Much like any airfoil...it must move to the area of lower pressure but in this case it rotates. I do not see any problem if you are not experiencing any high temperatures or noises coming from the SSS clutch. Cheers and keep me posted if conditions change.

 

[facetoface]

no, there is no noise and temp is normal but only there is some oile is dropped may be from mechnical seal and this is normal as approved from my desginer

 

[facetoface]

but can you give some web site to be more familiar for this phenomenon ,please

 

[turboco1]

visit friendster.com
join for free
ask to join a group named "Grupo Mio" there we can talk more about your plant and location, etc... I've traveled all over the world since 1975 for a couple of oem's and independently and find that it is a very small world in this business and maybe I've been to your plant or know your unit specifically. We cannot exchange emails here so that is why I set up Grupo Mio at Friendster.com

Take care and best of luck.

 

[turboco1]

sakram: the link and acrobat pdf file are here... the affect is not mentioned due to obvious reasons but if you look closely at the design of the ratchet teeth and the enclosure you can see that only this can be rotating the inlet side since with this SSS clutch you are either engaged or disengaged...no partial engagement. If there was any mechanical binding or friction type problem you would have a serious oil heating problem

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

 

[turboco1]

sakram:

the friendster.com group "Grupo Mio" is in the "Professional Organizations" Category and country is Puerto Rico.

 

[rmw]

In a double post Sakram states that the gear ratio of the gear box is 8:1. This would put the gear output shaft attached to the SSS clutch rotating at 89 X 8 = 712 RPM which means that the shaft is rotating at 1/2 the generator speed.

Even with that much speed the slip has to be enough to generate some heat somewhere. I am going with the hydrodynamic whip if there is no noise.

Still, at those relative speeds, there may not be enough centrifugal force generated for the pawl to make it fully retract.

rmw

 

[turboco1]

If the pawls (plural) are even "just" contacting the ratchet teeth at 1500 rpm... my guess is they would not be asking us for advice on why the GT LP is spinning but "why is the SSS smokin' and making lots of different noises...quickly please"

 

[facetoface]

Okky , the matter is clear but just for confirm , no 1- the ratchet teeth is conected with output shaft , so the ratchet is rotate with 1500rpm,
2-the low pressure inside the clutch comming from unstable flow inside the clutch,
3-be inform that the pressure of oil input 2 bar and output is vacuum pressure

 

[rmw]

turboco1,

You and I are on the same page regarding this. Your statement applies to any internal components pawl(s) or other wise, that are causing enough drag to make the gear shaft rotate at 1/2 the speed of the generator shaft. It would be a heck of a racket and lots of heat/smoke.

But, if it is lubricant drag, that produces heat too, so I would still suspect that the coupling was at an elevated temperature. The friction that would produce the rotation would also produce heat as it produced the motion.

On the other hand, it doesn't take a lot of torque to rotate even the largest turbine shaft once it is up on an oil film. Breakaway torque, now that is something else. So... can this turbine shaft be stopped from rotating by hand or some simple type of rotor brake? (Like wedging a board or plank against the shaft or coupling) And... if stopped, does it begin to rotate again once the braking effort is removed and enough time has passed so that the oil film is drained away? Are the turbine lube oil pumps on all this time that the PT shaft is turning?

rmw

 

[turboco1]

sakram:

1. The Output hub with the Pawls of the clutch is to the Generator shaft...these Pawls should be extended radially outwards away from the ratchet teeth during rotation. The actual RPM necessary to position these Pawls outward is unknown, maybe you know(?)

2. The Ratchet teeth are part of the Sliding component which is mounted on the Input Shaft or the Gear/PT drive train side

3. What exactly is vacuum pressure..."negative" pressure or actual vacuum?? if vacuum how could you have any oil leakage from the housing seals?

4. It is clear that the Pawls must NOT be extended radially outward FOR ENGAGEMENT with the ratchet teeth...so, the RPM of the Output hub (the generator shaft) must be:

a)below a certain value "X" of RPM and
b)Less RPM Than the Input Hub or Gear/PT drive train.

5. So it would appear that to engage the SSS, the Generator cannot be above "X" RPM, otherwise the Pawls cannot engage the ratchet to synchronize and move the sliding component into engagement.

6. Engaging:

a) the generator is at standstill, the PT is at standstill
b) the pawls are radially inward and engaged with the ratchet
c) the GT/PT rolls up in speed and drives the generator together up in speed
d) unit is synchronized and online


7. Disengaging:

a) the generator is unloaded and removed from service
b) the unit is at Full Speed No Load (FSNL)
c) The GT is cooled and taken off line and its speed decreases
d) the decrease in drive torque from the GT/PT and the free rotation of the generator with No Load causes the Generator to Over-run the GT/PT
e) the helical splines of the sliding component rotate causing the sliding component to move out of engagement
f) the sliding component slides all the way over but the Pawls are still extended radially outward at this high RPM
g) the Pawls and Ouput hub are reducing in speed due to the generator rotor decrease in speed
h) at some speed decreasing, the Pawls will contact the backside of the ratchet teeth, upon stopping of the generator, the Pawls will actually fall in to re-engage the ratchet teeth

Starting the steam turbine looking at the PT SSS clutch:

a) the generator just comes to speed and the Pawls are extened radially outwards and the Output hub is not contacting or engaged at all with the ratchet teeth.

b) the GT cannot be engaged at this high speed simply because the Pawls are extended radially outward by centrifugal force; the generator must be taken off-line and reduced in speed to engage the GT/PT

 

[turboco1]

rmw:

Right. The windage from the lube spray would cause heat and be noticeable. The unit has oil scavenging. Scavenging will reduce temperature excursions significantly by sucking the hot oil out as fast as or faster than it is sprayed into the housing. Aeroderivative GT's use oil spraying and scavenging chiefly just to cool the roller bearings but also to allow inverted flight maneuvers.

 

[turboco1]

sakram:

Look at what rmw is saying... you should verify that your oil scavenging temperatures have not increased over time. Simply due to windage you should be seeing a rise if there was no such windage problem before. How old is your concern about the PT rotating?? Is this a DAY ONE problem? or initially did the PT NOT rotate when operating on the steam turbine?

 

[turboco1]

sakram:

verify that your scavenge and supply lines are correctly mounted...that is not reversed.

 

[facetoface]

again, all parameter for tempratutre and pressure and vibration is normal , so no any physical changes
and for the vacuum pressure , it is for the tank of the return line of oil
but the idea for eng, disengage as foloow:
1-engage:SSS clutch of GT or ST will engage from starting if other is disengage beacuse the gen sped is zero
2- if other is running or gen is drived from one of them . the second is not engage until the power turbine speed reached to synch speed to keep 60 Hz at gen
just i need to know the shape od the input shaft is helical spline
2-

 

[facetoface]

again, all parameter for tempratutre and pressure and vibration is normal , so no any physical changes
and for the vacuum pressure , it is for the tank of the return line of oil
but the idea for eng, disengage as foloow:
1-engage:SSS clutch of GT or ST will engage from starting if other is disengage beacuse the gen sped is zero
2- if other is running or gen is drived from one of them . the second is not engage until the power turbine speed reached to synch speed to keep 60 Hz at gen
just i need to know the shape od the input shaft is helical spline
2- iam join with your web site but where is the categroy of prof org ,please