NON-FLOWING PRESSURE RESPONSIVE PILOT VALVE

摘要

NON-FLOWING PRESSURE RESPONSIVE PILOT VALVE A non-flowing pilot valve (16) for a control valve (C) in a main flow line (F) having a body (27) with an inlet fluid chamber (76), an outlet fluid chamber (106) and an intermediate fluid chamber (104) between the inlet fluid chamber (76) and the outlet fluid chamber (106). Diaphragm (34) in the fluid inlet chamber (76) is secured to a piston slidable body (40) extending within intermediate fluid chamber (104) and having a valve seat (88) thereon between inlet fluid chamber (76) and intermediate fluid chamber (104). A second fixed valve seat (64) is provided within the body (40) between the intermediate fluid chamber (104) and the outlet fluid chamber (106). A valve spool (92) has a pair of O-ring seals (94, 96) thereabout adapted to seal against the valve seats (88, 64). Unseating of the O-ring seals (94, 96) from the seats (88, 64) results from predetermined pressure changes in the sensed fluid pressure in fluid pressure chamber (76) and communicating such pressure changes through a fluid line (22) from the intermediate fluid chamber (104) to the control valve (C). An embodiment shown in Fig. 11 provides a delayed response to the control valve resulting from pressure changes in the sensed fluid pressure. The delayed response is obtained by a flow restriction (150) in a line (148) from an intermediate fluid chamber portion (144) which is separated by a diaphragm (140) from a balancing intermediate fluid portion (142).