Flapper valve protection

Abstract

An improved subsurface safety valve has a flapper plate which is held open by an operator tube, and which can be closed rapidly during high flow operating conditions without damage to the flapper plate or to the operator tube. The operator tube is telescopically coupled within a tubular piston. Retraction of the operator tube relative to the piston is yieldably opposed by a compression wave spring which is interposed between the operator tube and the piston. Telescoping retraction of the operator tube within the piston is limited by engagement of the operator tube against an internal shoulder of the piston. Damage to the flapper closure plate, pivot pin and operator tube is avoided by effectively decoupling the operator tube from the inertia load presented by the hydraulic piston and column of hydraulic control fluid. This is achieved by telescoping retraction of the operator tube within the piston as the flapper plate rotates through the critical throttling region into sealing engagement against the flapper valve seat. Because of its lower inertia, the operator tube is retracted rapidly through the spring housing in response to rotation of the flapper plate, thereby substantially reducing the magnitude of reaction forces which arise during dragging engagement between the flapper plate and the curved edge of the operator tube.