Offshore drilling rigs use “iron roughnecks” to make and break connections on the tubular items that are placed in and out of the well. These units are placed away from the well when drilling takes place; this unit was designed to allow the unit to be moved around various positions on the drill floor.
The turn table is aligned such that the “iron roughneck” can be transported across the turn table using the gear rack. This alignment is performed using a hydraulic powered rotating actuator. The weight of the “iron roughneck” is supported by multiple spherical rollers that can be seen.