Pilot-operated pressure-equalizing mechanism for subsurface valve

Abstract

A subsurface valve with a pressure-equalizing mechanism is provided to permit pressure above and below a valve closure member to equalize prior to the opening of the valve closure member. The pressure-equalizing mechanism may be installed, for example, in the valve closure member or in an annular housing in the subsurface valve. The mechanism includes a pilot activator disposed for reciprocal movement within a pilot bore. A flow tube that is disposed for longitudinal movement with a longitudinal bore of the subsurface valve is used to shift the pilot activator within the pilot bore from a closed or sealed position to an open or equalizing position. In the open position, fluid pressure below the valve closure member is allowed to flow through a pilot passageway that establishes fluid communication between the pilot bore and a cylinder within which a pilot piston is moveably disposed. Exposure of the pilot piston to fluid pressure below the valve member moves the pilot piston within the cylinder, which in turn moves an equalizing plug that is disposed for reciprocal movement within a plug bore from a closed or sealed position to an open or equalizing position. Movement of the equalizing plug to its open or equalizing position establishes fluid communication from below the valve closure member to above the valve closure member through an equalizing passageway. Pressure above and below the valve closure member is equalized through the equalizing passageway prior to the opening of the valve closure member by further downward movement of the flow tube.