Sealing Device for Steam Turbines and Method for Controlling Sealing Device

Subject: To provide a sealing structure, and control method therefor, which improve sealing performance between a rotating region and a fixed region, prevent fins from being damaged, and prevent increases in the amount of steam leakage from any clearances newly formed by further abrasion of an abradable material. Solution: The sealing structure in which free-cutting spacers 28 on a sealing base plate 25 and sealing fins 24 on a rotor 18 are opposed to each other is provided, in the sealing structure of which the sealing base plate 25 is disposed so as to be movable in an axial direction of the rotor 18. When a steam turbine 3 increases in load, a pressure head 30 moves in an axial steam-pressure loading direction of the rotor 18 and the sealing base plate 25 connected to the pressure head 30 moves in the axial steam-pressure loading direction. Since the free-cutting spacers 28 at positions opposed to those of the sealing fins 24 existing after the movement of the sealing base plate are maintained in a non-contact state, clearances between the sealing fins 24 and the free-cutting spacers 28 are dimensionally minimized.