Directing against the rubbing phenomenon appeared between movable part and stationary part due to high temperature difference of the upper and lower casings at the reheat governing valve end of intermediate pressure(IP) cylinder in steam turbine no.2 of one power plant

the thermal condition in structure of the steam turbine proper has been analysed

pointing out that the joint effect of different heat exchange and thermal insulation problems resulted from sandwiched cooling steam of IP cylinder upon upper and lower casings has made the temperature difference between them to reach 86 ℃

greatly surpassing the defined value of 50 ℃

seriously jeoparadizing safe operation and service life of the equipment. Through stoppage of extracting steam to the high-pressure heater no.3 without delay before deparalleling the unit

the temperature difference value has been decreased to 50.1 ℃

and through replacement of thermal insulation material of the steam turbine proper

the temperature difference value between upper and lower casings has reduced to 10 ℃

having basically solved the above-mentioned problem. At the same time

combined with the structure of steam turbine for 600 MW unit

a retrofit scheme of additionally installing steam-retarding plates in sandwich of lower casing of the IP cylinder has been put forward.