Figure 9-12.-Top-head drive ISO/air-transportable water well drilling rig.
of 10 mph over unpaved roads and has a cross-country
rough terrain capability.
The ITWD derrick consist of the telescoping mast
structure, the pulldown/pullback mechanism, the
top-head assembly, and the hoist assembly. Other
components are a stabilization system, main frame,
handling equipment, hydraulics, control console, and so
The drill derrick system is capable of generating
15,000 pounds pulldown and 30,000 pounds pullback
force through the top-head during the drilling operation.
The top-head drive is a variable speed drive that imparts
rotation and torque to the drill pipe for drilling and has
an rpm range from 0 to 200 rpm. The tophead drive is
mounted to a carriage that is free to move up and down
over the length of the moving mast section. The tophead
drive also has a hollow spindle for injection of air or
mud, giving the ITWD capabilities for rotary air or
rotary mud drilling.
The hoist system is attached to the side of the derrick
and operates independently of the derrick operation and
is rated for a 3,000-pound hook loading. This capacity
is sufficient to add and remove 18.5-foot drill pipes and
to set typical 20-foot casing and surface pipe. The hoist
is capable of lifting up to 180 feet of 4 1/2-inch drill pipe
when tripping out the drill hole. When increased
hoisting is required for lifting longer drill strings, the
top-head drive that has a capacity equivalent to its