| 摘要 |
A pressure operated safety or relief valve is set forth. It is constructed with a valve body enclosing a movable valve member positioned above a fixed cylindrical structure having a flow passage through it. A coil spring in a bonnet mounted above the valve member bears against the valve member and moves it into closure with a seat on the top of the cylindrical structure. The valve member includes a seal ring for sealing engagement with the seat for closure. When the valve member is opened, the valve member separates to permit pressure flow which then is directed through an annular gap between a surrounding skirt of the valve member and the exterior of a blowdown ring disposed on the cylindrical structure. The valve member snaps open, because with slight opening of the valve member, increased area beneath the valve member is acted upon by the inlet pressure to snap the valve member open. The area of such annular gap is varied with respect to the size of the flow passage through cylindrical structure so as to vary the pressure of escaping fluid in such gap. Such pressure is applied to the top of the valve member via a flow passage between the valve member and a surrounding sleeve. Pressure above the valve member causes the valve member to snap close then the pressure in this inlet drops to a predetermined level. The vented fluid is discharged through an outlet passage.
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