| 摘要 |
<p>The invention provides a drill string flow control valve (10) and method of use to minimize u-tubing of fluid flow in drill strings. The control valve comprise a valve housing (18), a valve sleeve (20) axially movable within a valve housing between an open and closed position, a piston (70) axially movable within said valve housing and disposed to provide initial actuation of the valve sleeve, a biasing mechanism (24) biasing the valve sleeve into the closed position, a static pressure port (80) for actuating said piston utilizing internal fluid pressure within said valve and a plurality of dynamic pressure ports (46, 50) allowing a differential pressure to be exerted on the â¢valve sleeve during dynamic flow conditions. The differential pressure exerted on the valve sleeve arises from an upstream pressure and a downstream pressure during fluid flow through said valve and is used to control operation of the valve.</p> |
