Method of two-stage flow control

摘要

A valve has a major valve closure member with a valve stem for opening and closing a major port in a valve chamber. An alternate flow path extends through the major valve closing member. Flow is controlled through the alternate flow path by directing a minor valve actuating fluid through the valve stem to apply pressure on a minor valve piston in the major valve closure member to move a minor valve closure member in the major valve closure member between a closed mode in which the minor valve closure member closes the alternate flow path and an opened mode in which the minor valve closure member opens the alternate flow path. The minor valve actuating fluid is sealed from the alternate flow path by a flexible diaphragm positioned between the minor valve actuating fluid and the minor valve piston, so the pressure of the minor valve actuating fluid is applied to the minor valve piston via the flexible diaphragm.

主权项

1. A method of providing two-stage flow through a valve comprising:
positioning a major valve closure member in as major flow path between a valve chamber and a port that is movable between an opened mode in which fluid can flow past the major valve closure member and through the port and a closed mode in which the major valve closure member blocks flow between the valve chamber and the port; providing an alternate flow path through the major valve closure member and positioning a minor valve closure member in the major valve closure member in a manner such that the minor valve closure member is movable between an opened mode in which fluid can flow through the alternate flow path and a closed mode in which the minor valve closure member blocks flow of fluid through the alternative flow path; actuating the major valve closure member to move between the closed and opened modes for the major valve closure member by moving a major valve stem that is connected to the major valve closure member; and actuating the minor valve closure member to move between the closed and opened modes of the minor valve closure member by directing a minor valve actuating fluid through the major valve stem to apply a minor valve actuating fluid pressure to a minor piston that is positioned in the major valve closure member and that is operatively connected to the minor valve closure member in the major valve closure member.