| 摘要 |
<p>Drill string check valve apparatus comprises a tubular body and a flapper valve mounted in the body with a flapper movable between an open position and a closed position. An axially extending valve retainer is also mounted in the body and is translatable from a running position to a drilling position. In the running position the valve retainer extends through the valve to maintain the flapper in the open position. In the drilling position the valve retainer permits the flapper to move to the closed position to prevent flow up through the body.</p> |
