a special device that, when fitted in to the master bushing, transmits torque to the kelly and simultaneously permits vertical movement of the kelly to make hole. It may be shaped to fit the rotary opening or have pins for transmitting torque. Also called the drive bushing. See kelly.
KB. The heavy bushing at the rotary table, through which the kelly passes, which transmits the rotary motion of the rotary table to the drill pipe. The top of the bushing is often taken as a depth datum.
n: a device fitted to the rotary table through which the kelly passes and the means by which the torque of the rotary table is transmitted to the kelly and to the drill stem. Also called the drive bushing.
Part of the drilling rig, the Kelly is a long hollow steel bar that connects to the upper end of the drill string.
Drilling rig equipment that fits inside the rotary table and is also used as a reference point on logs to calculate depth.
a piece of equipment which fits around the kelly at the point where it passes through the rotary table. It is often used as a datum from which to measure the depth of a well.
An adapter that serves to connect the rotary table to the kelly. The kelly bushing has an inside diameter profile that matches that of the kelly, usually square or hexagonal. It is connected to the rotary table by four large steel pins that fit into mating holes in the rotary table. The rotary motion from the rotary table is transmitted to the bushing through the pins, and then to the kelly itself through the square or hexagonal flat surfaces between the kelly and the kelly bushing. The kelly then turns the entire drillstring because it is screwed into the top of the drillstring itself. Depth measurements are commonly referenced to the KB, such as 8327 ft KB, meaning 8327 feet below the kelly bushing.