| abstract |
Drill string flow control valves and more particularly, drill string flow control valves for prevention of u-tubing of fluid flow in drill strings are provided. Drill string flow control valves may comprise a valve housing, a valve sleeve axially movable within a valve housing from a closed position to an open position, a piston axially movable within said valve housing and bearing against the valve sleeve, a biasing mechanism for biasing the valve sleeve into the closed position, a static pressure port for actuating said piston utilizing internal fluid pressure within said valve and a plurality of dynamic pressure ports for allowing a differential pressure to be exerted on the valve sleeve during dynamic flow conditions. The differential pressure exerted on the valve sleeve may be the result of an upstream pressure and a downstream pressure during fluid flow through said valve. By allowing a differential pressure resulting from a fluid flow to act on the valve sleeve, u-tubing in a drill string can be prevented or substantially reduced. Methods of use are also provided. |