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Section 1 Maintenance
SCC1000C Crawler Crane — Maintenance Manual
14�5�2 Use and Maintenance of Chain Slings
14�5�2�1 Correct Use of Chain Slings
Select the correct slings to be used before a lift
by taking the following into consideration: number
of legs, diameter of the chain, Working Load Limit
(WLL), and Working Load Limit at different sling
angles in the case of multi-leg slings.
Use of chain slings must comply with relevant
regulations and safety requirements. Chain lings
shall not be twisted or kinked. Never drag slings
from under loads when the load is resting on the
sling.
Sharp edges and corners in contact with the slings
should be padded to prevent damage. A regulator
can be used to avoid shock loading and to maintain
balance as necessary. The load attached to a hook
shall be centered in the bottom of the hook bowl
and never tip load the hook. Never use the chain
slings in contact with acidic solution or fumes,
as which may cause corrosion, embrittlement
mechanism or cracks to the slings. If the slings
may come into use in such conditions, consult the
manufacturer rst. Never galvanize or subject the
chain sling to electroplating, coating or any plating
treatment involving heating or acid washing without
the approval of the manufacturer. A qualified
expert shall perform risk assessment and make
corresponding adjustment to Working Load Limit
(WLL) before lifting a load that is important or
dangerous.
Ensure that the chain slings are in accordance
with the requirements of the order before initial
use and that a test certicate is attached, on which
information like Working Load Limit (WLL) and
identification is in compliance with that identified
on the sling. Inspect chain slings for damage and
wear before each use. Correct any problem found
as per the maintenance regulations. Static weight
of the load shall not exceed the Working Load Limit
(WLL) of the chain sling.
Follow these conditions to protect the slings from
twisting or tilting in a lift:
(1) For single leg chain slings, the contact point is
right above the center of gravity of the load.
(2) For two leg chain slings, the contact points
distribute on both sides above the center of
gravity of the load.
(3) For three or four leg slings, the contact point
shall distribute evenly on the plane above the
center of gravity of the load and the legs had
better distribute evenly as well.
For multi-leg chain slings, select the correct type
of sling and contact points to ensure that each leg
angle β is within the permissible range specified.
All the leg angles are recommended to be the
same. The leg angle β shall not be less than 15
degrees. The hook shall match with the lifting point
and the load shall be centered in the bowl, other
than the tip, of the hook. Position hooks of multi-leg
slings facing outward from the load in spite of the
specially structured hooks used in unconventional
conditions. For a load without proper lifting point,
the chain sling shall contain the load from under
the load and the Working Load Limit (WLL) shall
reduce to the 80% of the rated load. Make sure
that chain slings will not kink in double-sling
contain lift and that angle β shall not be greater
than 60 degrees. The Working Load Limit (WLL) is
conventionally calculated on the basis that all legs
of the chain sling are applied with equal load. For
multi-leg chain slings, each leg bears unequal load
if the angles between legs are different and the leg
with smallest angle bears the most load. In extreme
conditions, the load is totally applied to the vertical
one among all legs. The load is still considered as
being evenly distributed in the following conditions:
(1) The load does not exceed 80% of the Working
Load Limit (WLL) of the sling.
(2) All the leg angles are not less than 15 degrees.
(3) All leg angles are equal or the maximum
deviation from each other is 15 degrees. Except
for the above conditions, the Working Load
Limit (WLL) shall reduce by 50%. The operator
shall keep hands and other parts of the body
clear to avoid injury when tensioning chain
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