| 摘要 |
A pilot valve assembly 14 hydraulically controls a pressure reducing valve 12 to maintain or vary the outlet pressure P2 of the pressure reducing valve in response to increased flow therethrough. The pilot valve assembly 14 comprises a first movable valve member (56, 58, 62, 64, Fig. 2) and a second movable valve member (60, 72, 78, Fig. 2). The first and second moveable valve members are 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 outlet pressures to open and close the pilot valve 14 and thus the main valve 12 to both maintain or vary the outlet pressure P2. |
