| 摘要 |
A flapper valve housing 320 has an upper piston 324 which is remotely controlled to move upwards to a position in which flapper valve clement 396 is rotated by torsion spring 398 from a position retained in annular space 406 to a position blocking the production bore which is offset from the centre of the valve housing. A lower piston 326 is actuated to move upwards to a position in which the flapper valve element is locked and the assembly is capable of providing differential containment both from below and above the valve. |
