Patent ID: 6513594
Filing Date: 2003-02-04
Classification: E21B

Abstract:
A subsurface safety valve for controlling a fluid flow through a well conduit comprising:a housing having a bore and disposed within an annulus defined by the space between the well conduit and the housing; a valve closure member movable between an open position and a closed position, and adapted to restrict the fluid flow through the bore when in the closed position; a flow tube moveably disposed within the housing and adapted to shift the valve closure member between its open and closed positions; a piston assembly including a piston member in sliding relationship with a cylinder, the piston member in mechanical communication with the flow tube, the piston member having a first seal, a second seal, and a third seal, each seal sealing against the cylinder, and the third seal disposed between the first and second seals; and a failsafe passageway in fluid communication with a balance pressure line and a portion of the piston member between the first and second seals.