| 摘要 |
The method involves releasing a drill pipe which is fixed axially in the preset direction, by performing rotating movement in the opposite direction. An outer bar (5) is driven by a rotary drive before the rotational position of the outer bar is checked, during the axial displacement of the drill pipe. The rotational position of the rod is determined based on the preset signal from a preset sensor by comparing the rotational position of the outer bar and rotational position of the drill drive. The rotational position of outer bar is determined. |
