Kelly bushing

Drilling Equipment & Components

In conventional rotary drilling, the kelly bushing is the device that fits into the master bushing of the rotary table and transmits torque to the kelly (the square or hexagonal pipe at the top of the string). As the rotary table turns, the kelly bushing turns, driving the kelly.

It contains rollers that allow the kelly to move vertically (drill down) while torque is being applied. While obsolete on Top Drive rigs, understanding the kelly system is fundamental to drilling mechanics history.