Wire Rope and Wire Rope Slings
Every Lift Uses 1 of 3 Basic Hitches
VERTICAL,
or
straight,
attachment
is
simply using a sling to connect a lifting hook
or other device to a load. Full rated load of
the sling may be used, but never exceeded. A
tagline should be used
on
such a lift
to
pre-
vent rotation which can damage thesling. A
sling with a hand-tucked splice can unlay
and fail
if
the sling is allowed
to
rotate.
affects the ability of the wire rope compo-
nents to adjust during the lift, places angu-
lar loading on the body
of
the sling, and
creates a small diameter bend in the sling
body at the choke point.
BASKET hitches distribute a load equally
between the two legs of a sling, within limi-
tations imposed
by
the angles
at
which legs
are rigged to the load. (See discussion of
sling angles below.)
CHOKER hitches reduce lifting capability
of
a sling, since this method
of
rigging
Basic Factors Concerning Use
of
Wire Rope Slings
1.
RATED
LOAD
(Rated
Capacity)
of
a wire
rope
sling is
based upon the Nominal,
or
Catalog, Strength
of
the wire
rope used in the sling,
AND
FACTORS which affect the
overall strength
of
the sling. These factors include ATTACH-
MENT or
SPLICING EFFICIENCY, the number
of
parts
of
rope in the sling, type
of
hitch (e.g., straight pull, choker
hitch, basket hitch), DIAMETER AROUND WHICH THE
BODY
OF
THE SLING IS BENT, and the diameter
of
pin
(or hook) over which the eye
of
the sling is rigged.
2. RATED LOAD
of
a sling is different for each
of
the three
basic methods
of
rigging (See graphic above.). These rated
loads are available from your wire rope sling supplier and
may be indicated on the tag attached to the sling at the time it
is fabricated (if requested
by
the user).
3. WARNING: A hand-tucked eye splice can unlay (unravel)
and fail
if
the sling is allowed to rotate during use.
4. NEVER "SHOCK LOAD" A SLING. There is no practical
way to estimate the actual force applied by shock loading.
The rated load
of
a wire rope sling can easily be exceeded by
a sudden application
of
force, and damage can occur to the
sling. The sudden release
of
a load can also damage a sling.
S.
The
BODY
of
a wire rope sling should be
PROTECTED
with corner protectors, blocking
or
padding against damage
by sharp edges
or
corners
of
a load being lifted. Sharp bends
that distort the sling body damage the wire rope and reduce
its strength.
6. ANY ANGLE other than vertical at which a sling is rigged
increases the loading on the sling.
7. A sling should be given a VISUAL INSPECTION BEFORE
EACH LIFT
OR
USAGE to determine
if
it is capable
of
safe-
ly making the intended lift.
An
inspection should include looking for such things as:
• Broken wires.
• Kinks
or
distortions
of
the sling body.
• Condition
of
eyes and splices, and any attached hardware.
• Reduction in diameter
of
the rope.
• Any damage.
• Corrosion.
S.
Whenever a sling
is
found to be deficient, the eyes must be
cut,
or
other end attachments
or
fittings removed to prevent
further use, and the sling body discarded.
9. A SLING EYE should never be used over a hook
or
pin with
a
body
diameter larger than the natural width
of
the eye.
NEVER FORCE AN EYE ONTO A HOOK. The eye should
always
be
used
on
a
hook
or
pin
with
AT
LEAST
THE
DIAMETER
OF
THE ROPE.
Sling Angles Affect the
Load
On
the
Legs
of a Sling
SLING ANGLE (also called Angle of Loading)
is the angle measured between a horizontal line
and the sling leg or body. This angle is very
important and can have a dramatic effect on the
rated load of the sling.
As
illustrated here, when
this angle
DECREASES, the LOAD ON EACH
LEG
INCREASES.
This
principle
applies
whether one sling is used with legs at an angle
in a basket hitch, or for multi-leg bridle slings.
Horizontal sling angles
of
LESS THAN 30
DEGREES SHALL NOT BE USED
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