Abstract: An improved pilot valve assembly (14) for hydraulically controlling a pressure reducing valve (12) to maintain and further vary the outlet pressure (P2) of the pressure reducing valve (12) in response to increased flow (f) through the valve (12). The pilot valve assembly (14) comprising first and second movable valve members (100,102). The first and second moveable members (100,102) being acted on by a velocity head pressure sensed by a downstream Pitot tube (90) and a downstream outlet pressure (P2) in a balanced arrangement such that they move in response to both the velocity head and downstream pressure (P2) to open and close the pilot valve (14) and so main valve (12) to both maintain and vary the outlet pressure (P2).

Abstract: A flow control valve includes a body member (1) having a bore (10) defining a fluid flow passageway. A resiliently-biased flow control member (2) is mounted in said passageway for movement relative to the body member (1) in response to the differential fluid pressure across the valve. The flow control member (2) includes a flow control port (28) that defines with a probe element (44) an annular throttling orifice (46). The probe element (44) is tapered such that the size of the annular orifice (46) depends on the position of the flow control member relative to the probe element. (FIG.

Abstract: A flow control valve includes a body member (1) having a bore (10) defining a fluid flow passageway. A resiliently-biased piston member (2) is mounted in said passageway for movement relative to the body member (1) in response to the differential fluid pressure across the valve. The piston member (2) defines an annular throttling orifice (28) between said piston member and said bore. At least a portion (10a) of the passageway has a non-uniform cross-section, such that the size of the annular orifice (28) depends on the position of the piston member relative to the body member.