Stop valve and steam turbine

A stop valve, comprising:

• a valve seat part which is provided in a flow path through which steam flows;
• a valve disc which closes the flow path by coming into contact with the valve seat part;
• a rod part which extends along a central axis and in which an end portion on a first side in a central axis direction is connected to the valve disc;
• a rod-urging part which urges the rod part toward the first side in the central axis direction to close the valve seat part by the valve disc;
• an actuator part which linearly moves the rod part toward a second side in the central axis direction against an urging force of the rod-urging part when being connected to the rod part;
• and
• a connection-switching part which is able to switch a connection state between the rod part and the actuator part between a connected state and a non-connected state,
• wherein the connection-switching part includes:
• a concave engaging part which is formed over the entire circumference of an outer circumferential surface of the rod part and recessed from the outer circumferential surface of the rod part in a radial direction centered on the central axis;
• a casing which has an accommodation space joined to the concave engaging part formed therein by covering the rod part from the outside in the radial direction to surround the concave engaging part and provided to be connected to the actuator part and to be able to be in sliding contact with the outer circumferential surface of the rod part;
• a plurality of frame pieces which are disposed in the accommodation space and in which a part thereof protrudes from the outer circumferential surface of the rod part while being accommodated in the concave engaging part;
• a sleeve part which is disposed in the accommodation space to be able to be in sliding contact with the casing, and is able to move between a frame piece accommodation position in which the frame pieces are accommodated in the concave engaging part and a frame piece detachment position in which the frame pieces are separated from the concave engaging part;
• and
• a gas introduction part through which a gas is introduced into the accommodation space,
• the sleeve part moves from the frame piece detachment position to the frame piece accommodation position when the gas is introduced into the accommodation space, and
• the casing comes into contact with the frame pieces disposed at the frame piece accommodation position when being moved toward the second side in the central axis direction.