Fail safe hydraulic piloted pressure reducing and regulating valve

A fail safe hydraulic piloted pressure reducing and regulating system for supplying fluid power to subsea equipment comprising,

• a hydraulic piloted pressure reducing and regulating valve positioned underwater and connected to and supplying regulated pressure to subsea equipment, said valve including a body and a control piston, and a pilot piston, and spring means between the pilot piston and the control piston whereby the valve is regulated in response to hydraulic pilot pressure applied to the pilot piston,
• said underwater valve including a rod connected to the pilot piston, and a locking sleeve engaging the rod and releasably locking the rod and pilot piston against movement, said body including a port in communication with the space between the rod and the sleeve for releasing the rod from the sleeve upon application of pressure to said port,
• a hydraulic signal pressure line connected to the pilot piston and extending to the water surface,
• a hydraulic lock line extending from the port to the water surface,
• an air piloted pressure reducing and regulating valve above the water having an outlet connected to the hydraulic signal pressure line, said air piloted valve having inlet connected to a hydraulic fluid supply,
• an air control system connected to the air pilot valve for controlling the outlet pressure and the pressure in the hydraulic signal pressure line,
• a hydraulic switching valve positioned at the water surface and connected between a hydraulic supply and the hydraulic lock line to said port, said switching valve movable between a supply position and a vent position,
• said hydraulic switching valve connected to the air supply control system and actuated to the hydraulic supply position when the air supply is off and actuated to the vent position when the air supply is on.