| 摘要 |
<p>An improved shaft drill break-out system is disclosed that utilizes three separate out-put torques for the power swivel used to break-out, make-up and rotate the drill stem and attached drill bit for earth boring. When removing drill stem from the hole, the power swivel is tightened to the upper end of the drill stem with the largest torque. Thus, when the upper section of drill stem is lifted for breaking the bottom connection from the next lower section of drill stem, it is assured that this bottom connection will be broken since when going in the hole this connection was made-up with the intermediate torque. The lowest torque is used for drilling. As a consequence, sufficient torque for break-out is assured with proper selection of each of the three torques. Additionally disclosed are break-out arms and a slip assembly adapted for selected engagement with vertical slots in the drill stem to facilitate make-up and break-out.</p> |
