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These include the engines, and the hoisting, rotating, and mud
systems.
The engines supply the power to the rig. Most local rigs use a
single engine to power the drawworks and rotary table. Power is
usually transmitted through a modified heavy truck type powershift
transmission (automatic). These engines are diesel fueled and are rated
between 425-550 hp. The power is used primarily to turn the drill
string and raise and lower equipment in the well.
Engines also supply the electricity used on and around the rig.
Electrical power is supplied, usually, through two generator sets. The
rig can run with one of these units but it would run at close to
maximum output at night. The second provides for back-up, and
allows for other options. These engines are generally rated at 300-350
hp. They are housed on a skid and are enclosed; this unit is referred to
as a "light plant".
Rigs also employ 1 or 2 engines to power the mud pump. Total
output varies from 300-500hp. When two engines are used they must
be tuned to match and are hooked together through a gear box. One of
these engines runs clockwise while the other runs counter-clockwise.
Power for most these application is through a clutch with an over
centre release mechanism - they can be locked in the released or
engaged position.
The hoisting system is used to raise and lower and to suspend
equipment in the well. The drilling line (wire rope) is usually braided
steel cable about 1 1/8 inches in diameter. It is wound around a reel in
the draw works. The engines are connected to the draw works and let
the drilling line in or out. The derrick or mast is the steel tower. If the
tower comes on a tractor-trailer and is jacked up, it is a mast. If the
tower is erected on the site, it is a derrick. The drilling line goes over a
pulley, called the crown block, at the top of the derrick, and then down
to another pulley called the traveling block. Below the traveling block
is a hook to which equipment can be attached. As the drilling line is

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