In a well safety valve for controlling the fluid flow through a well conduit in which the valve has a housing and a tubular member controlling a valve element the improvement in means for opening and closing the valve.SAFETY VALVES At least one piston is telescopically movable within and has its longitudinal axis within the wall of the housing and outside of the tubular member and engages the tubular member. The first side of the piston is in communication with a hydraulic passageway adapted to extend to the well surface for opening the valve. Water Pump Control ValvesThe second side of the piston extends into a closed gas chamber tending to move the valve to the closed position. The piston has a small cross-sectional area for reducing the pressure effect in the gas chamber of the gas caused by movement of the second side of the piston whereby the differential between the opening and closing forces are reduced thereby allowing the valve to be used at greater depths in the well. Preferably, valve means is positioned in the piston for charging the gas chamber.Instrumentation Ball Valves In one embodiment the gas chamber and the hydraulic passageway are positioned out of communication with the tubular member thereby eliminating the need for seals on the tubular member for enclosing portions of the gas chamber or hydraulic passageway. In another embodiment the valve closure member is positioned between the first and second sides of the piston allowing the use of a shorter tubular member providing a shorter safety valve.

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