Pressure reducing valve control

A pilot valve assembly for controlling a pressure reducing valve having an inlet and an outlet, the pilot valve comprising:

• a housing;
• a first moveable member moveably mounted within the housing, and comprising:
• a hollow shaft having an internal bore;
• first and second diaphragms fixed axially spaced apart along the shaft and moveably mounted within the housing, the first and second diaphragms dividing the housing with the first diaphragm and housing defining a velocity head chamber at one end of the first moveable member, the second diaphragm and housing defining an outlet chamber at the opposite end of the first moveable member, and an inlet chamber defined between the first and second diaphragms and interconnected with the bore of the shaft;
• and
• an outlet nozzle mounted on an end of shaft within the outlet chamber and connected to the internal bore of the hollow shaft;
• a second moveable member moveably mounted within the housing with the first and second moveable members also being moveable relative to each other, the second moveable member comprising:
• a third diaphragm defining a portion of the outlet chamber;
• a yoke mounted on the third diaphragm and extending within the outlet chamber;
• and
• a valve seat supported by the yoke and opposing the nozzle to variably restrict the flow of fluid from the nozzle as the first and second moveable members are moved relative to each other;
• a Pitot tube located within the outlet of the main valve for sensing the velocity head of a flow through the outlet, the Pitot tube being connected to both the velocity head chamber and via a modulation valve to the outlet chamber;
• an inlet duct connected to the inlet chamber and via a control chamber of the pressure reducing valve to the inlet of the pressure reducing valve;
• and
• an outlet duct connected to the outlet chamber and to the outlet of the pressure reducing valve.

A pilot valve assembly for controlling a pressure reducing valve, the pilot valve comprising:

• a first movable member including a hollow tubular supply ring having an internal bore that is connected to an inlet of the pilot valve for supplying fluid to a nozzle that is mounted upon a radially inner portion of the supply ring for discharging fluid radially inwardly of the supply ring;
• and
• a second moveable member including a pilot valve seat that opposes the nozzle;
• wherein the first and second moveable members are movable relative to each other to move the valve seat relative to the nozzle to variably restrict the flow of fluid from the nozzle and through the pilot valve from the inlet.

A pilot valve assembly for controlling a pressure reducing valve, the pilot valve comprising:

• a housing;
• a first moveable member moveably mounted within the housing and comprising first and second diaphragms spaced apart along the first moveable member and moveably mounted within the housing, the first and second diaphragms defining a fixed volume inlet chamber therebetween that is moveable within the housing with the first moveable member and which is connected to an inlet of the pilot valve;
• and
• an outlet duct that is connected to the inlet chamber and which is variably opened and closed as the first movable member moves within the housing to control the pressure reducing valve.