| 摘要 |
A fire safe valve having a valve body with a flow passage therethrough and a valve chamber intersecting the flow passage a valve closure member having a stem and being slidable in the valve chamber to open or close flow through the flow passage, a shoulder on the stem, a bonnet connected to the body, said bonnet having a bore through which the stem extends, a seat surrounding the stem and adapted to be engaged by the stem shoulder on backseating, means sealing between the stem and the bonnet bore outward of said seat, an actuator connected to move said stem and said valve closure member, a sleeve surrounding a portion of the stem, fusible material supporting the sleeve in a normal stop position to limit the outward movement of the stem to prevent backseating, melting of the fusible material allowing the sleeve and stem to move so that the stem backseats, and means associated with said sleeve to control the actuator whereby on movement of the sleeve the valve closure member is moved to closed position. |
