Valve-operating system

Claim 1

In a system for the power opening and closing of at least two main valves, a power operator of the hydraulic type connected to each of said valves and adapted to be energized by application of hydraulic liquid to operate the same, control valves of the fourway type connected to each of said operators and movable between two operating positions for controlling application and discharge of liquid from the same, electro pneumatic means associated with each of said four-way valves for setting the same, each of said means including a pneumatic operator mechanically connected to the associated four-way valve and two solenoid valves connected to control supply of pneumatic pressure to said pneumatic operator, said pneumatic operator exerting force to move the associated four-way valve from one operating position to the other, electrically energizing one of said solenoid valves serving to energize the pneumatic operator to move the associated four-way valve to cause the main valve to be closed, and electrically energizing the other solenoid valve serving to supply pneumatic pressure to the pneumatic operator to move the associated four-way valve to cause the power operator to open the valve, an electrical operating circuit connected to each of said solenoid valves, each circuit including a source of electrical power and a switch adapted to be closed or opened to selectively operate the associated solenoid valve, a vent line connected to each of said first one of said two solenoid valves, the other one of said solenoid valves being arranged to vent to the atmosphere, and means responsive to a failure of the electrical power connected to said circuits for supplying pneumatic pressure to both of said vent lines to provide overriding pneumatic pressure to said pneumatic operators, thereby ensuring that the four-way valves will be positioned to maintain the valves closed or to close the same.