| 摘要 |
A rotationally operated back pressure valve includes a flapper valve with a sliding stinger tube located thereabove in a housing. An operating mandrel has a lower end portion received in a bore of the housing and the operating mandrel extends upward out of the upper end of the housing. The operating mandrel may be connected to a work string for rotation by the work string. A threaded engagement is provided between the operating mandrel and the stinger tube so that the stinger tube can be selectively moved between a first and second position thereof relative to the housing in response to selected right-hand or left-hand rotation of the operating mandrel relative to the housing. In the first position of the stinger tube it is located above the flapper valve so that the flapper valve closes the housing bore. In the second position of the stinger tube it extends downward through the housing bore past the flapper valve to hold the flapper valve fully open. The tool includes locking lugs which lock the operating mandrel against rotation relative to the housing if tension is applied across the tool. This allows other tools located in the work string below the back pressure valve to be actuated by work string manipulation. When a compressional load is applied across the valve, the locking lugs disengage so as to allow rotational operation of the back pressure valve.
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