Pressure balanced safety valve for wells and flow lines

Abstract

A safety valve for the production tubing of wells and/or fluid flow lines includes a valve element having both linear and rotary components of movement within a valve body and is actuated by a lost-motion rack and pinion gear actuating mechanism. The clam-shell pinion gear is moved linearly within the valve body by a hydraulic sleeve piston actuator for inducing valve movement responsive to hydraulic control of the sleeve piston. The sleeve piston is also responsive to upstream pressure for pressure actuation of the valve to its closed position. The valve element is also mechanically movable to its closed position. To facilitate opening movement of the valve, after an initial part of the opening movement of the sleeve piston assembly has occurred, pressure upstream of the valve element is communicated with the downstream side of the valve element, thus balancing pressure across the valve element and dissipating any pressure induced resultant forces that oppose valve opening movement. A lost-motion, spring biased sleeve piston interconnection between upper and lower piston sleeve sections is constructed to allow collapsing of the piston sleeve assembly but restrains separation of the sleeve sections. The sleeve interconnection also protects piston springs from torque forces during rotation of the piston sleeve.