Figure 13-48.—Fleet angle of winch.
in figure 13-48. The distance from the drum to the
sheave is the controlling factor in the fleet angle.
When you are using vehicle-mounted winches, the
vehicle should be placed in a position which permits the
operator to watch the load being hoisted. A winch is most
effective when the pull is exerted on the bare drum of
the winch. When a winch is rated at capacity, the rating
applies only as the first layer of cable is wound onto the
drum. The winch capacity is reduced as each layer of
cable is wound onto the drum because of the change in
leverage, resulting from the increased diameter of the
drum. The capacity of the winch maybe reduced by as
much as 50 percent when the last layer is being wound
onto the drum.
Ground Angle
If the hoisting line leaves the drum at an angle
upward from the ground, the resulting pull on the winch
will tend to lift it off the ground. In this case, a leading
block must be placed in the system at some distance
from the drum to change the direction of the hoisting
line to a horizontal or downward pull. The hoisting line
should be overwound or underwound on the drum as
may be necessary to avoid a reverse bend.
Fleet Angle
The drum of the winch is placed so that a line from
the last block passing through the center of the drum is
at right angles to the axis of the drum. The angle between
this line and the hoisting line as it winds on the drum is
call the fleet angle. As the hoisting line is wound in on
the drum, it moves from one flange to the other, so the
fleet angle changes during the hoisting process. The
fleet angle should not be permitted to exceed 2 degrees
and should be kept below this if possible. A 1 1/2-degree
maximum angle is satisfactory and will be obtained if
the distance from the drum to the first sheave is 40
inches for each inch from the center of the drum flange.
The wider the drum of the hoist, the greater the lead
distance must be in placing the winch.
RIGGING SAFE OPERATING
PROCEDURES
All personnel involved with the use of rigging gear
should be thoroughly instructed and trained to comply
with the following practices:
1. Wire rope slings must not be used with loads
that exceed the rated capacities outlined in enclosure (2)
of the COMSECOND/COMTHIRDNCBINST
11200.11. Slings not included in the enclosure must be
used only according to the manufacturer’s
recommendation.
2. Determine the weight of a load before
attempting any lift.
3. Select a sling with sufficient capacity rating.
4. Examine all hardware, equipment, tackle, and
slings before using them and destroy all defective
components.
5. Use the proper hitch.
6. Guide loads with a tag line when practical.
7. When using multiple-leg slings, select the
longest sling practical to reduce the stress on the
individual sling legs.
8. Attach the sling securely to the load.
9. Pad or protect any sharp corners or edges the
sling may come in contact with to prevent chaffing.
10. Keep the slings free of kinks, loops, or twists.
11. Keep hands and fingers from between the sling
and the load.
12. To avoid placing shock on the loading slings,
you should start the lift slowly.
13. Keep the slings well lubricated to prevent
corrosion.
14. Do not pull the slings from under a load when
the load is resting on the slings; block the load up to
remove the slings.
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