| 20120000671 | Method for Withdrawal and Insertion of a Drill Pipe String in a Borehole and Also a Device for Use When Practising the Method - A device for tripping, in which, at a drill-floor opening which is arranged to receive a pipe string, two or more cooperating pipe-handling units are arranged, each, independently of the other(s) or in cooperation with the other(s), being arranged to releasably hold the pipe string fixed and to move the pipe string in its axial direction, and also to move a pipe section in the axial direction of the pipe string and rotate the pipe section around the axis of the pipe string. | 01-05-2012 |
