The fast cooling technology of steam turbine is the process that the cooling medium is used to accelerate the temperature reduction of cylinder and rotor after the shutdown of turbogenerator.

Large size parts generally refer to those parts with more than one meter long in each dimension, such as low-pressure cylinder of steam turbine, wing panel of plane and so on.

Scheduled overhaul on a steam turbine costs long time and much money, and the turbine body and auxiliary equipment are often found in good conditions when the cylinder is opened.