Kelly bars are key components in the execution of boreholes by hydraulic rotary drilling rigs. They transfer the torque of the rotary drive and the crowd pressure of the crowd system concurrently to the drilling tool. A kelly bar consists of 2-5 telescopic tubular sections with a system of drive keys and lock recesses, welded onto their outer  surfaces. Standard kelly bars are fabricated with a total of 6 drive keys on each section. The tubular kelly sections are manufactured from high-tensile steel to ensure minimum  weight at adequate strength.

A     全缩长度/ retracted   length

B      全 伸 长 度 /extended   length

B1  全仙长度锁定/ extended lengh (locked) 

D     运输长度/ transport   length

E     最人运输直径/transport  diameter  (max)