| 摘要 |
The invention is a pressure responsive shut-off valve including a valve housing that defines a fluid inlet and a fluid outlet separated by a valve seat. A valve closure accommodated by the valve seat moves between open and closed positions to control fluid flow between the inlet and outlet. Controlling the valve is a valve operator including a pressure responsive piston that moves between a set position in which the valve closure is separated from the valve seat and a release position in which the closure is seated on the seat to prevent fluid flow between the inlet and outlet. Retaining the piston is a cylinder body that defines an activating volume communicating with the inlet and establishing on one face of the piston a fluid pressure forcing the piston toward its release position, and a reference volume communicating with the inlet and establishing on the opposite face of the piston a reference volume. An internal seal isolates the inlet from the reference volume with the piston in its set position while allowing fluid communication therebetween with the piston in its release position. Maintaining the piston in the set position is a latching mechanism that, after activation of the piston to its release position by excessive pressure, can be restored by a manual reset.
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