| 摘要 |
A relief valve for use particularly for isolating and for permitting communication between flow passages in a well bore which may include parallel tubing strings connected by an H-Member and a single tubing string and a tubing-casing annulus which communicate through a side-pocket mandrel. The valve has a tubular housing having a lower open end and connected at an upper end with a packing mandrel provided with an annular packing assembly for sealing with a bore wall around the valve, a valve stem telescoping along an upper portion into the housing and extending along a lower end portion from the housing, shear screws between the valve stem and the housing for locking the valve stem at a lower valve-closed position, a plurality of spaced locking flanges along the stem and a lock ring within the housing operable with the flanges for locking the stem at a plurality of second valve open positions, a valve assembly on the lower end of the stem having an external annular seal for engaging a seal surface around the valve assembly at a valve-closed position of the stem and valve assembly, shear means between the valve assembly seal and a core portion of the assembly for emergency release of the seal, and the valve stem being sized in length to engage a stop surface in the housing at a valve open position to limit movement of the valve assembly toward the housing to prevent damage to the valve assembly.
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