| 摘要 |
Closed head power tongs used to make up and break threaded pipe joints are disclosed herein. The closed head power tong have removable mating inserts that allow the gripping aperture of the power tongs to be increased so that objects larger than the gripping diameter of the tongs can be raised or lowered through the center aperture of the power tong without removing the tongs from alignment with the drill string.
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