| 摘要 |
<p>In accordance with an illustrative embodiment of the present invention, a valve apparatus adapted to be incorporated in a string of tubing to permit pressure testing thereof in a well bore includes inner and outer members telescopically disposed and movable between extended and contracted relative positions, main valve means for closing the axial flow passage through said members to downward flow in response to extension of the members, and equalizing passage and valve means for equalizing pressures across the main valve prior to reopening thereof in response to contraction of the members.</p> |
