| 摘要 |
A drill string flow control valve may comprise a valve housing, a valve sleeve axially movable within a valve housing from a closed position to an open position, a biasing mechanism biasing the valve sleeve into a closed position, and a plurality of pressure ports for allowing a differential pressure to be exerted on the valve sleeve. The valve may include a piston axially movable within the valve housing and bearing against the valve sleeve which piston may be used to initiate movement of the valve sleeve. The piston includes a flow passage therethrough in fluid communication with the interior of the valve sleeve and a ball valve disposed to control fluid flow through the piston. The valve may include a flow restriction in the flow path within the valve sleeve and disposed between pressure ports formed in the wall of the valve sleeve. Methods of use are also provided.
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