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11 HOISTING SYSTEM

Hook and hook-block combination

A simple spring hook has been successfully used in the
industry for many years. Sometimes it’s been updated to increase
the capacity level, concerning safety and production facilities. The
hook must possess a quite wide throat containing elevator links
and swivel bail.
A triple hook with one big safe hook for the swivel bail and
two smaller ones on both sides of the main hook, serving as hoist’s
bail lifting was beneficial, while being firstly introduced but it cost
a lot.
Average hooks are considered to be very durable, but when
they are used up they are replaced by triple hooks with the
capacity of 500 tons or more.
In order to reduce the total cost and required plumb space the
triple hook-travelling block interfaces have become popular.

Hoisting system

Within the hoisting system while binding the crown block
and travelling block together by means of the wire rope, the line
pull’s thrust force is increased, and the drilling string of a
significant weight up can lift up and down. Blocks and ropes
operate like a composite constructive pulley system to provide the
necessary mechanical advantage and increase loading level. Such
power increasing is implemented in the pulley system of any kind
on account of swiftness loss. That’s why the hoisting drum should
reel on more rope than travelling block takes for the appropriate
distance while moving up and down (Fig. 11.1).
In fact you should apply specific efforts to make a rope
move to revolve a sheave. Because of the great amount of
variables used for such effort you may get in practice 2 per cent of
applied power for each rope line.

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