Page 281 - 4637

mounted, hydraulic power unit (HPU) applies fluid to the wheel
cylinders for steering.

Figure 18.2 – Mobile drilling rig with integral-wheel complex

Although the rigs' substructures are 30-ft tall, the 40-ft
distance between each tire provides excellent stability during rig
moves. The structural design embodies a fixed-lift system
consisting of a lift beam, hydraulic lift cylinders, and the HPU.
The whole drill floor and mast are jacked up against the lift beam
and suspension system by stroking the lift cylinders.
This system picks up the entire rig with the mast in a vertical
position. The process is a very quick operation and saves the effort

280