Rolling of 600MW Steam Turbine

This may answer your ?

Why IP turbine rolling is done but not HP rolling

Did the company that created and installed the thing produce a User Manual for it? What does it say?

The user manual mentions about initial IP turbine rolling...but why cant we do the usual HP turbine rolling??

"The user manual mentions about initial IP turbine rolling..."

Because your user manual says so! You may not...

"Do the usual HP turbine rolling."

ROLLING OF TURBINE THROUGH IPT DURING GENERATOR

DRY OUT (UNITS HAVING HP-LP BY PASS)

The turbine is required to be run at 3000 rpm on no load, for very long duration, when generator dryout operation is being carried out. Such no load operation may be required for about 30-40 hours or sometimes even more than this Working of turbine under such abnormal conditions, causes the exhaust hood temperature to rise beyond the permitted limit. In order to control the rise of exhaust hood temperature, it is recommended to roll the turbine through IP cylinder, thereby increasing steam flow through IP & LP cylinders The HP cylinder is kept under vacuum under such operation. By adopting this method of rolling the turbine from cold state for generator dryout it has been foreseen that the exhaust hood temperature can be kept within the permitted limit.

These instructions are valid only for the units which have HP/LP bypass stations. Prior to steam rolling the unit. relevant protections and interlocks should be got checked. The other systems like oil system. Condensate system vacuum system etc. should be put into service as per the normal procedure given in operation manual.

For starting the turbine from the cold state, the following instructions to be followed:

1. Close tightly the bypass valves of NRV in the cold reheat line, so as to stop the entry of the steam in the HP cylinder when HP bypass station is put into operation.

2. Open both the HP cylinder evacuation valves, so that the HP cylinder is kept under vacuum throughout the running of the set.

This has relevantly answrd all. my queries..thank you so much sir.