| Rotating
During the
70's, rotary drilling rigs with a movable rotary drive were developed,
particularly in Germany. These were capable of installing up to 6 m long
casings during drilling. As all reaction forces resulting from the drilling
process are transferred to the base carrier via the mast, the maximum
torque available is about 4 kNm with maximum vertical down or up-ward
forces of 4 kN. This method is therefore limited to casing diameters of
1500 mm and to drilling depths of up to 30 m.
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