Cable Pulling Principles - Torin BIG RED T32052 Manual Del Propietário

CABLE PULLING PRINCIPLES

Pulling cable is a complex process. This section of the manual describes and explains four main topics of
pulling cable:
• Each cable pulling system component
• How these components work together
• Forces that are generated
• Procedures for the cable puller operator to follow
While reading through this section of the manual, look for components that are shaded in the illustrations. The
shading indicates components that are associated with the text.
Greenlee strongly recommends that each member of the cable pulling crew review this section of the manual
before each cable pull.
Cable Pulling Systems
Pulling cable requires a system of components. At a minimum, a cable pulling system will include a cable
puller, a cable pulling rope, and connectors to join the rope to the cable. Most systems will also include, but
are not limited to, a cable puller anchoring system, pulling sheaves and sheave anchoring systems.
The cable puller has a maximum amount of pulling force, which is the amount of pulling tension that it
develops. Every other component of the pulling system has a maximum rated capacity, which is the amount of
pulling tension that it can withstand. The maximum rated capacity of every component must meet or exceed
the cable puller's maximum pulling force.
Pulling Theory
This section introduces the main ideas involved with pulling cable.
Pulling Resistance
The cable puller must overcome two types of resistance: gravity and friction.
Gravity constantly exerts its force on the vertical portions of the run. When the pulling force is relaxed,
gravity attempts to pull the cable downward. Friction develops where the cable contacts the sheaves, conduit
and tray. Friction resists any movement, forward or backward, and tends to hold the cables in place.
To accomplish a cable pull, the cable pulling system must develop more force than the combination of gravity
and friction.
Generating Pulling Force
To generate pulling force, the capstan works as a force multiplier. The operator exerts a small amount of force
on the rope. The cable puller multiplies this and generates the pulling force.
This pulling force is applied to the rope, connectors, and cable in order to accomplish the pull. The direc-tion
of force is changed, where necessary, with pulling sheaves.
At the Pulling Rope
The product of a force (f) moving through a distance (d) is energy (f x d), and may be measured in
newton-meters or ft-lb. Energy is stored in a rope when the rope is stretched. This is similar to the way energy
is stored in a rubber band when it is stretched. Failure of the rope or any other component of the pulling
system can cause a sudden uncontrolled release of the energy stored in the rope.
For example, a 100 meter nylon rope with a 50,000 newton average breaking strength could stretch 40 meters
and store 1,000,000 joules of energy. This is enough energy to throw a 900 kilogram object, such as a small
automobile, 113 meters into the air.
A similar double-braided composite rope could store approximately 300,000 joules of energy. This could throw
the same object only 34 meters into the air. The doublebraided omposite rope stores much less energy and
has much less potential for injury if it were to break.
Double-braided composite rope is the only type of rope recommended for use with the Ultra Tugger cable
puller. Select a double-braided composite rope with an average rated breaking strength of at least 143 kN
(32,000 lb).
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