When talking about steam turbine outages, every one now a days wants to minimize the duration, one of the ways to reduce barring time after reducing the machine load to zero .. therefore i have chosen that topic for discussion. To start I put following queries.

What is the recommended temperature of HP Steam rotor Stage 1 at which we can stop the turning gear?

What is the recommended temperature of HP Steam rotor Stage 1 at which we insulatio of the turbine casings can be removed safely.

Either forced cooling is recommended or not.

regards
Azhar

It is recommended to stop turning gear as the HP cylinder temperature reaches 150 C. One should start Forced air cooling at casing temperature of 350 C. The temperature drop rate must not increase 25 C per hour. This high cooling rate doesnot effect the metallurgy of the turbine. But during cooling it is possible that you may find mechanical contact of blades in the cylinder. Lagging should be removed at 200 C