I have a query,

On a multi shaft unit we can run the GT up to crank speed to force cool.
This would reduce the time on an inspection and off line wash.

Q: How on a single shaft can this be achieved?

I have thought about this and have considered ways in to do this, but am I correct.

·Run the unit up to crank speed with seal steam on from auxiliary supply and vacuum pulled, close all inlet valves to ST.
This should force cool the GT and ST at a controlled rate.

·Wait until the GT wheel space temps are down to 60/70c on barring, and then run up to crank speed with seal steam on and vacuum pulled, close all inlet valves to ST.

·Or is it a case of barring the unit until all temps (GT & ST) are low enough to crank unit.

If this is the case this will add three to four days to an inspection outage, will it not?

 

What has the packager said you need to to do perform an off-line water wash? Or does their procedure presume the unit is cool to start with?

This sounds reasonable to me; it seems you've taken the steam turbine into consideration by enabling the steam seals and bringing up vacuum and making sure the steam inlet valves are closed (including any warm-up, bypass or bowl drain valves which would prevent establishing vacuum).

But, I would suggest you run this by the packager for their review and comment. 9FBs are pretty new, and yours might still be under warranty so give the packager a chance to comment so if something unexpected happens they don't void your warranty.