Abstract: A maintenance method for a steam turbine including a rotor, a casing for accommodating the rotor, and a bearing box for accommodating a bearing which supports the rotor includes: a step of installing an expansion-and-contraction member below the rotor by using an upward facing flat surface disposed between the casing and the bearing box in an axial direction; and a step of pushing up the rotor upward by the expansion-and-contraction member.

Abstract: A first seal member includes a double-structure bellows in corrugated form, and vibration control device provided on the outside of the bellows such as to cover part of the bellows. A flat portion that is not in corrugated form is provided in part of the bellows. The vibration control device is provided in circumferential direction on an outer surface of the flat portion, and made up of a ring-shaped rib having a plurality of holes in a circumferential direction and weights inserted in the holes provided in a wall of rib. Natural frequency is adjusted by adjusting the number of weights, thereby preventing resonance between the natural frequency of the first seal member and the rotational frequency of rotor from occurring.

Abstract: A first seal member 21A according to a first embodiment of the present invention includes a double-structure bellows 22 in corrugated form, and vibration control means provided on the outside of the bellows 22 such as to cover part of the bellows 22. A flat portion 23 that is not in corrugated form is provided in part of the bellows 22. The vibration control means is provided in a circumferential direction on an outer surface of the flat portion 23, and made up of a ring-shaped rib 25 having a plurality of holes in a circumferential direction and weights 26 inserted in the holes provided in an outer wall of the rib 25. Natural frequency is adjusted by adjusting the number of weights 26, thereby preventing resonance between the natural frequency of the first seal member 21A and the rotational frequency of a rotor from occurring.