Condensing Turbine Won't Rotate After 2 Days Shutdown

Are you able to visually inspect turbine? Is it possible that when you stopped the turbine, one of the fins stopped dead center at the steam inlet? This would prevent it from turning.

We can´t turn the shaft of turbine either with barring gear nor manually and are not able to inspect turbine without dismantling,what we want to avoid it if possible.

We stopped and started turbine many times the same way and even for longer time but never had such troubles

My steam plant experience was in the military. Never got too deep into the turbine itself.

If it won't turn, there's a problem. While I'm not an expert, I think you're going to have to dismantle to find the culprit, I can't think of anything else.

Contact manufacturer to see if they can offer any insight. Sorry I couldn't be of more help.

My guess is that something went wrong when repairing barring gear or before.

What went wrong to cause you to shut down in the first place?

What caused the barring gear to be broken?

Turbine was stopped because of planned inspection of boiler.Until then was turbine running as swiss watches.

Barring gear was checked after change of broken gear-weels,it turned properly.

We do not know what could cause damage of barring gear.It was found out by attent to start.It is possible it happened by start when shaft was already blocked or by shutdown or both.You are rigtht that damage of barring gear could indicate reason but no idea about it.

We already called service comp but I am affraid that result will be shutdown of turbine for a few weeks even months.In any case thanks for help.

I am assuming that your reference to the Barring gear would be what I would call the "jacking gear". This would have been engaged when all power was removed from the turbine and the jacking gear-motor run for a day or two until the turbine was sufficiently cool to eliminate the possibility of your shaft warping. It does take quite a while for a large unit to cool and I seem to recall 2 days being the norm aboard ship.

If this was not the case then I would surmise that perhaps you have a warped shaft.

The other possibility if the the cool down was proper is that someone did not properly engage and disengage the jacking gear and it is locked or jammed into place preventing any movement. It may even be that the disengaging mechanism lost a pin or broke and it is not disengaging completely. I am assuming that it was not engaged until after the rotor came to a COMPLETE stop.

Somehow the idea of the shaft warping seems to be a strong possibility. As I recall the only way out of that is to slowly heat up the unit with some auxiliary steam while jacking it over which can be a very delicate and time consuming proposition.

If the jacking gear is a worm drive then any backlash could well have jammed it or broken a shear pin.

Turbine is running (until now)!

People from service disconnected coupling between turbine and gearbox and could be able turning the rotor.After checking all possible (gearbox,bearings etc..) wasn´t found nothing defective only by starting of turbine we found that quick opening valve didn´t close completely thus steam was leaking through it in closed position and temperature of turbine housing was increasing rapidly.Difficult to say if this was a reason...

So basically with steam leaking into the turbine when it was stopped and not turning over, the rotor could have warped enough to prevent rotation when coupled through the gearing to the generator. With that extra inertia removed they were then able to rotate the rotor and let it straighten out. Like I said, it is very important to properly cool down a unit especially on the longer ones like yours probably is.

A sister ship to one I was on, had the Astern throttle valve mis-assembled in the shipyard and something like a 1/4 turn open when supposedly shut. On the maiden voyage the Astern stop valve developed a slight leak and after almost 2 weeks running down to South Africa at full throttle ahead, with steam leaking into the astern turbine,3 days out of Capetown the astern turbine threw blades and they had to be towed into Capetown.

The not so funny part was that it took them longer to remove the overhead duct work to allow opening the casing then the actual work itself. Plan ahead someone did not.

To Spinco: thank you for feedback,it makes sense

now,we are dealing with vibrations and increased temperature of axial bearing on the opposite side to generator.(turning device´s side)

Temperature goes up to 105 C and bearing is noisy.Vibrations measurement doesn´t show dramaticly increased vibrations but there is still heard increased noise.Could be this as result of previously problem?

If you didn't do proper cool down when taking off line, yes..........slightly warped shaft. Since the barring gear was found to be broken, I assume the shaft was not rotated during cool down period. This would explain it.

I'll second that because it's one of the few scenarios that fits all the clues. Being able to rotate the turbine after uncoupling wouldn't necessarily correct the warp-age although I am surprised that there wasn't a quicker response when starting up to the problem. It could be that the amount of curvature was small enough so there wasn't noticeable scraping noises as it was started.

I also recall that whether the turbine is mostly impulse or reaction stages has a lot to do with the clearances within the turbine and the type of inter-stage sealing in the design might affect the amount of noise.

However, once up and running the imbalance caused by the warp-age would eventually lead to bearing failure. I am more used to shipboard installations where a HP and LP feed into a double reduction gear unit and the jacking gear engages the gear and both turbines are rotated by their connection to the gearing. The HP has to cool down from a much higher temperature but the LP has more mass due to its larger diameter. I also seem to remember that the HP tends to be more impulse staging whereas the LP is more reaction staging.

My experience was ship board also. Main engine room on a destroyer. Sounds like the barring gear performs the same function as the reduction/jacking gear on ship.

The warpage may be small, almost imperceptible, but when the turbine is brought up to speed, it becomes more apparent, hence the sound.

This is not a good problem to have and I'm not sure how to fix it. My guess would be to engage the now working barring gear and feed the turbine LP auxiliary steam to keep it hot and just rotate for several days, maybe a week, and see if it straightens out.

I don't know what size or RPMs of his set up, but running full bore with a warped shaft could potentially lead to catastrophic failure.

I am assuming that your reference to the "axial" bearing would be the "Thrust" bearing such as a Kingsbury tilting shoe thrust bearing.

Reviewing your previous comment that the barring gear "was" working but later found broken and that there was steam leakage due to a faulty "quick stop" valve makes me think about the possibility that while the unit was turning over, the steam leaking through the valve was putting a good deal of thrust onto the axial bearing and if by chance the lube oil pump to the thrust bearing is shaft driven off the turbine then the flow of oil to the thrust bearing at the slow speed may have been insufficient to provide the oil wedge that make these bearings work. It could be that you wiped some but not all of the tilting or fixed shoes that make up the bearing.

It would account for the fact that you were able to start after proper pressure was supplied. It would also give rise to the possibility of some axial displacement causing the lack of rotation at the initial attempted start up