Friction kelly bar of rotary rig

b The external keys of frictional pressuring kelly bar has three or six straight keys, there is no large concave pressuring table in the middle, and there are three or six wear-straight bar in the internal key. When the driving force rotates, the internal key of the driving sets push the straight bar of the external key of kelly bar, to drive the kelly bar rotary.the peripheral force is produced when the kelly bar rotaries, which pass pressure to produce the friction. The function of passing pressure is usual, the kelly bar is generally used for soft layer or drift sand formation. Grinding resistance pressuring kelly bar is usually formed by 5-6 sections.with the drilling depth in the range of 50-90 meters.