Tosiba 300mw steam turbine rotor long, short etc. 1

[Dickf62]

Hope I am in the right place for this.

I have a toshiba 300mw steam turbine that whent down on HP diff. expansion we lost stages 5 to 12 what I need to know is what should be done when you have the following problems.

1. Rotor Long and just going into alarm
2. Rotor Long and in red zone
3. Rotor short and just going into alarm
4. Rotor short and in red zone
5. High Bearing temp

And what are some other Abnormal operations to look for and what to do for them.

Thanks for the information

 

[byrdj]

Going into rotor Long is due to trying to load the unit too quickly and not matching the throttled steam conditions to the turbine metal. If the event is from a Cold start, then prewarming may have been inadaquate.

When in a long condition, the correction is to lower the steam tempurture being admitted to the turbine. besides boiler firing controls, transferring from full to partial arc will help.

Once long alarm is reached, and there are no ways to reduce steam to metal mismatch, the unit will need to be returned to turning gear. I have seen it take 8 to 12 hours to get back to normal due to not prewarming.

When the unit is tripped, it will go slightly longer as the speed decays. The centerpedal makes the rotor short.

Going Short---the steam got to cold. so opposite actions to get steam temp back up or trip out

bearing hot--- shut down, verify sight glass drain flow, watch for very rapid increase in temp on coast down.


Was your rotor long damage the result of trying to load too quick from a cold start?

 

[Dickf62]

I dont think it was due to loadading too quick from a cold start, we were on steam temp matching for 3 hours, had a 136 min soak at 800 rpm's and 20 min soak at 3600 then on grid 38 mw soak for 20 min started increasing load then the dodo hit the fan...

 

[byrdj]

For a cold start, that sounds quick to me, but my experance is with older GEs. Normally, 4 to 6 on TG pressurized getting rotor up to 300F, 120 to 180 minutes at 3000 to get LP up to 200F, then 60 minutes at 30MW to get LP to 350. While at same time the HP should have increased from 300 to ~750 (450F over the 3 to 4 hours since roll)

For a rotor to go long that much I would expect the steam at the turbine had to be 200F hotter than the turbine casing.

Did you have wet insulation?

 

[Dickf62]

Ok here is what we had
on T/G for 2 weeks
Rolled S/T @ 0317 start
HP upper metal inner casing metal temp 144f
HP lower metal inner casing metal temp 141f
IP upper metal inner casing metal temp 127f
IP lower metal inner casing metal temp 131f
IP crossover 143f
LP induction 289f


0335 S/T at 800 rpm a 136 min soak this is a auto

HP upper metal inner casing metal temp 200f
HP lower metal inner casing metal temp 196f
IP upper metal inner casing metal temp 130f
IP lower metal inner casing metal temp 136f
IP crossover 167f
LP induction 289f

0632 S/T at 3600 rpm a 20 min soak

HP upper metal inner casing metal temp 257f
HP lower metal inner casing metal temp 252f
IP upper metal inner casing metal temp 193f
IP lower metal inner casing metal temp 216f
IP crossover 333f
LP induction 401f

0652 S/T on grid Auto Load to 15 MW 20 min soak

HP upper metal inner casing metal temp 270f
HP lower metal inner casing metal temp 262f
IP upper metal inner casing metal temp 233f
IP lower metal inner casing metal temp 262f
IP crossover 391f
LP induction 412f

0710 started raising load on S/T

HP upper metal inner casing metal temp 291f
HP lower metal inner casing metal temp 274f
IP upper metal inner casing metal temp 293f
IP lower metal inner casing metal temp 327f
IP crossover 453f
LP induction 421f

1st stage inner surface metal 584f
1st stage outer shell surface 497f

at this point everything was going as normal

the HP dif went from .49 at start to .293 but this has been normal and as we load up it would come back but this time it didnt.

 

[byrdj]

I need to state, I'm not familiar with Toshiba nor the newer configurations.

Is this a dual admission configuration? I don't know the term LP induction. but if this is an LP admission, i would think there needs to be some cooling steam going thru the HP. So if this is the case, check the valving for HP reverse flow

From My experance, that HP shell was way to cold to roll the unit. and by being cold the shell will be short. addidng any heat to the rotor either by steam (or windage) would make it grow long rapidly.

So with out getting deeply envolved with some configuration drawings, more operation data and OEM instructions, I want be able to add any more.

Maybe some else can