rotation speed
rotation speed
(OP)
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
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





RE: rotation speed
rmw
RE: rotation speed
RE: rotation speed
RE: rotation speed
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
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SSS needs tweaking
RE: rotation speed
RE: rotation speed
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
RE: rotation speed
RE: rotation speed
rmw
RE: rotation speed
RE: rotation speed
----------------------------------
One day my ship will come in.
But with my luck, I'll be at the airport!
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htt
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
RE: rotation speed
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RE: rotation speed
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.
RE: rotation speed
RE: rotation speed
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RE: rotation speed
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.
RE: rotation speed
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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.
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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.
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htt
RE: rotation speed
the friendster.com group "Grupo Mio" is in the "Professional Organizations" Category and country is Puerto Rico.
RE: rotation 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
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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
RE: rotation speed
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
RE: rotation speed
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
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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.
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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?
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verify that your scavenge and supply lines are correctly mounted...that is not reversed.
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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-
RE: rotation speed
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
RE: rotation speed
see:
http://www.ul.ie/~nolk/gears.htm#Gear%20types
scroll about 25% down from Top of fully loaded page: Single and Double Helical Gears
I copied the link to Grupo Mio, use after you log in.
htt
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sakram's problem is a well known problem when using SSS clutches and the GT is shutdown.
some GT OEM's (like GE) installed brakes (solenoid actuated) to stop the GT shaft from turning by viscous drag created by the SSS.
The whole shaftline should be fed by the same lube oil system (single shaft combined cycle configuration) in case the there is a loss of L.O. pressure - the low lube oil pressure trip will protect all the units.
i have seen this before and there is no problem... except that there is a nuisance to see GT rotation when there should be none.
the only problem is if there is a need to restart the turbine and the unit does not have flying re-start capability... i.e. a start signal needs a zero speed detection in order to be accepted.
aeroderivative units usually use a hydraulic cranking system so flying restart should not be an issue.
SSS is a very helpful crowd... they will surely be able to suply info regarding this issue and offer solutions.
Also, the GT OEM should be able to assist to implement the brake solution.
In industrial type units (wrongly called heavy duty) the inertia of the shaft is enough to keep the shaft at zero speed once the brakes are released. May be in aeroderivative units you will need to apply the brakes permanently... the power turbine turns so smoothly that you can actually turn it by hand (i've done it).
HTH.
saludos.
a.
RE: rotation speed