these will have half of the load. To find the size of the
line to use, calculate what size fiber line in a threefold
block will lift 5 tons. It works out to about 4 1/2
TACKLE SAFETY PRECAUTIONS
In hoisting and moving heavy objects with blocks
and tackle, stress safety for people and materials.
Always check the condition of blocks and sheaves
before using them on a job to make sure they are in
safe working order. See that the blocks are properly
greased. Also, make sure that the line and sheave are
the right size for the job.
Remember that sheaves or drums that have
become worn, chipped, or corrugated must not be
used because they will damage the line. Always find
out whether you have enough mechanical advantage
in the amount of blocks to make the load as easy to
handle as possible.
Sheaves and blocks designed for use with fiber
line must not be used for wire rope since they are not
strong enough for that service, and the wire rope does
not fit the sheave grooves. Also, sheaves and blocks
built for wire rope should never be used for fiber line.
HOOKS AND SHACKLES
Hooks and shackles are handy for hauling or
lifting loads without tying them directly to the object
with a line or wire rope. They can be attached to wire
rope, fiber line, or blocks. Shackles should be used
for loads too heavy for hooks to handle.
Hooks should be inspected at the beginning of
each workday and before lifting a full-rated load.
Figure 4-34, view A, shows where to inspect a hook
for wear and strain. Be especially careful during the
inspection to look for cracks in the saddle section and
at the neck of the hook.
When the load is too heavy for you to use a hook,
use a shackle. Shackles, like hooks, should be
inspected on a daily routine and before lifting heavy
loads. Figure 4-34, view B, shows the area to look for
You should never replace the shackle pin with a
bolt. Never use a shackle with a bent pin, and never
allow the shackle to be pulled at an angle; doing so
will reduce its carrying capacity. Packing the pin with
washers centralizes the shackle (figure 4-34, view B).
Figure 4-34.Hook and shackle inspection (views A and B)
and packing a shackle with washers.
If you need a hook or shackle for a job, always get
it from Alfa Company. This way, you will know that
it has been load tested.
Mousing is a technique often used to close the
open section of a hook to keep slings, straps, and so
on, from slipping off the hook (figure 4-35). To some
extent, it also helps prevent straightening of the hook.
Hooks may be moused with rope yarn, seizing wire,
or a shackle. When using rope yarn or wire, make 8