sling. The total weight of the load is carried
by a single leg with the sling angle of 90
degrees.
Bridle Hitch
The bridle hitch can consist of two,
three, or four single hitches (fig. 3-22), used
together to form a bridle hitch for hoisting an
object.
The bridle hitch provides excellent load
stability when the load is distributed equally
among the legs, the load hook is directly over
the center of gravity of the load, and the load
is raised level. The use of a bridle sling
requires that the sling angles be carefully
determined to ensure that the individual legs
are not overloaded. It is wrong to conclude
that a three- or four-leg bridle hitch will
safely lift a load equal to the safe load on one
leg multiplied by the number of legs, because
there is no way of knowing that each leg is
carrying its share of the load. With a four-
legged bridle sling lifting a rigid load, it is
possible for two of the legs to take practically
the full load while the other two only balance
it. COMSECOND/COMTHIRDNCB strongly
recommend that the rated capacities for two-
leg bridle slings listed in the COMSECOND/
COMTHIRDNCBINST 11200.11 series be used
also as the safe load of three- or four-leg
bridle hitches.
Sling Angle
The rated capacity of any sling depends
on the size, the configuration, and the angles
formed by the legs of the sling and the
horizontal. A sling with two legs used to lift a
1,000 pound object will have 500 pounds of the
load on each leg when the sling angle is 90
degrees. The load stress on each leg increases
as the angle decreases; and if the sling angle
was 30 degrees lifting the same 1,000 pound
object, the load will be 1,000 pounds on each
leg. Try to keep all sling angles greater than
45 degrees; sling angles approaching 30
degrees are considered extremely hazardous
and must be avoided at all cost.
Sling Safe Working Loads
It is a difficult task to remember all of the load,
size, and sling combinations; however, the following
Figure 3-22.—Bridle hitch.
rules of thumb work well for estimating the
loads in the most sling configurations.
The rules of thumb are based on the
safe working load of the single vertical hitch
of a particular sling. The efficiencies of the
end fittings used also have to be considered
when determining the capacity of the
combination.
3-23
