Full opening check valve

Abstract

In accordance with the invention, a full opening check valve is provided which will close in response sustained high velocity flow through the valve. In one embodiment, a downhole blowout preventer is provided having a rigid outer sleeve which may be interspaced within a casing string near its lower end for insertion into a bore hole. The downhole blowout preventer has an inner sleeve including an upwardly longitudinally collapsible tube within the outer sleeve. The tube may be composed primarily of rubber or the like. The inner sleeve includes a surface for developing an upwardly acting collapsing force responsive to the upward flow of well fluids through the blowout preventer. The inner sleeve resists the action of the collapsing force developed by the upward flow of well fluids at ordinary velocities during ordinary operation, but increased upward flow velocities of well fluids associated with downhole blowouts develop a larger collapsing force sufficient to overcome the resistance of the inner sleeve and collapse the tube upwardly and inwardly within the outer sleeve, thereby blocking the bore hole. Preferably, the tube is reinforced with rigid hoops and flexible strands to promote the inward overlapping folding of the tube upon collapse. The resistance of the tube to collapse under ordinary flow may be the result of bonding agents, shearable pins, friction, weight or the longitudinal stiffness of the tube within the outer sleeve. In another embodiment, the inner sleeve is adapted to collapse in response to a sustained high velocity flow in either direction. This embodiment may be used in pipelines such as pressurized gas collection or distribution lines to isolate breaks in the system.