| 摘要 |
A shutoff valve for closing off flow through a fluid line includes a stem 28 axially movable relative to a valve body 12. A valve element 22 is carried by the stem 28 for engagement with a seat 20 to close off fluid flow through the valve, and is biased toward the seat by valve closure spring 40. The swivel body 52 is pivotally connected to the upper end of the stem, and may be rotated to allow the spring 40 to force the valve element into engagement with the seat. A fusible link mechanism 64 is carried by the swivel body for engagement with the valve body to rotate the swivel body to the valved closed position. The mechanism 64 includes a piston 66, a spring 70, and a fusible material for normally acting as a solid stop to prevent the spring 70 from moving piston 66 to rotate the swivel body to the valve closed position. According to the method of the invention, the solid state of the fusible material is altered when the valve is subjected to an elevated temperature, thereby allowing the spring 70 to move the piston 66 to automatically rotate the swivel body and close the valve.
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