| 摘要 |
PCT No. PCT/NO96/00310 Sec. 371 Date Jun. 24, 1998 Sec. 102(e) Date Jun. 24, 1998 PCT Filed Dec. 23, 1996 PCT Pub. No. WO97/24507 PCT Pub. Date Jul. 10, 1997An apparatus for a derrick, comprising two or more hydraulic piston-cylinder arrangements (10, 11) for raising and lowering a yoke (8) which travels on guide rails (7) in the derrick (1) itself, where two or more wire lines (13) are strung over sheaves (12) rotatably attached to the yoke. The wire lines (13) are attached at one end thereof to the top drive (9) and at the other end thereof are secured to an attachment point (14a, 14b) adjacent to a drill floor (2), said two or more wire lines being run in two sets (13a, 13b) of lines. The attachment points (14a, 14b) for each wire set are connected to a tension equalizer assembly to equalize differences in tension in the wire lines.
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