660 MW Turbine

Read operation & maintenance manual supplied along with equipment by OEM. You may definetely get a procedure for it. For fast cooling you can just pour water, but it may be detrimental to the health of the machine. based on facilities available, you can decide about purging with cool gas, but take OEM into confidence.

Don't try it unless you want to spoil some one elses expensive equipment. jsut think about thermal gradients and what they can do. Afterall the cooling rate is considered not only to maintain the gradient across length but also to suck the heat out of the core of the rotors and the casing body. While cooling you have to keep on barring the turbine and something cools faster than planned and you might hear a small sound which would be large one when the machine is restarted.

For such big turbines please follow instructions of manufacturer only. Cooling of turbines do not means lowering of temperature only, the expansion of various parts happened due to high temperature of operation has to come back to cold condition meassurements as the cooling happens. Temperatue gradient across various parts should not cross the limits specified in the manufacturer's manual.

Never ever try to put water or condensate in the turbine for cooling.