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catheads to move heavy equipment around the rig floor. One floorhand drigged up
one end of the catline to the object they wished to move. Another wrapped the other
end of the catline around the cathead and used it to lift the object. Today, rig
personnel use a small, air-powered hoist to move equipment on and around the rig
floor. They are separate from the drawworks and are called air hoists or air tuggers.
Air hoists are so much easier to use than a friction cathead that, today, about the only
time you might see a friction cathead being used is in an emergency.
While crew members seldom use friction catheads, they use mechanical or
automatic catheads a great deal. They employ an automatic cathead to make up or
break out the drill string when running it into or pulling it from the hole. It is called
an automatic cathead because the driller simply moves a control to engage or
disengage it. When engaged, an automatic cathead pulls on a wire rope or, in some
cases, a chain, to make up or break out the string. The automatic cathead on the
driller's side of the drawworks is the makeup cathead because it plays a part when the
crew makes up drill pipe. The automatic cathead on the other side of the drawworks
is the breakout cathead because the driller engages it to break out drill pipe.

The Blocks and Drilling Line

Manufacturers make drilling line from very strong wire rope. Drilling line runs
from 1 to 2 inches (22 to 51 millimetres) in diameter and is similar to common fiber
rope, but wire rope, as the name implies, is made out of steel wires. It looks very
much like what the rest of the world calls “cable” but is designed especially for the
heavy loads encountered on the rig.
The line comes off a large reel – a supply reel. From the supply reel, it goes to a
strong clamp called the “deadline anchor”. From the deadline anchor, the drilling line
runs up to the top of the mast or derrick to a set of large pulleys. This large set of
pulleys is called the “crown block”.
In the oilfield, the pulleys are termed “sheaves” (pronounced “shivs”). The
drilling line is reeved (threaded) several times between the crown block and another
large set of sheaves called the “traveling block.” Because the line is reeved several
times between the crown block sheaves and the traveling block sheaves, the effect is
that of several lines. The heavier the anticipated loads on the traveling block, the
more times the line is reeved between the crown and traveling block. For example, a
deep hole, where the load on the hoisting system will be great, calls for more lines to
be strung than for a shallow hole, where the load will be lighter. In figure 95, ten
lines are strung, which means the line was reeved five times between the crown and
traveling block. Ten lines can lift fairly heavy loads; so, only eight might be used for
lighter loads. For heavier loads, twelve or more could be strung.
Once the last line has been strung over the crown block sheaves, the end of the
line goes down to the drawworks drum, where it is firmly clamped. The driller then
takes several wraps of line around the drum. The part of the drilling line running from

the drawworks to the crown block is the fastline – fast because it moves as the driller
raises or lowers the traveling block in the mast or derrick. The end of the line that
runs from the crown block to the deadline anchor is the deadline – dead because it

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