The use of Swivels with Wire Rope
Under certain circumstances it may be necessary to use a
swivel in a lifting system to prevent rotation of the load.
This is typically done for employee safety considerations. It
is possible however, that the use of a swivel will have an
adverse affect on rope performance and may in some cases
damage the wire rope.
There are many types of accessories available that
incorporate different types and degrees of rotation
preventing swivels. The swivel may be either an
independent accessory or an integral part of a lifting device
such as a crane block with a swivel hook. A typical
independent accessory is a ball bearing anti-friction swivel.
There are also headache balls with swivel hooks.
The type of swivel that causes the most concern from the
standpoint of the wire rope is the independent anti-friction
swivel that attaches directly to the rope. The purpose of
using a swivel in a lifting system is to prevent rotation of the
load. This then allows the wire rope to rotate. Excessive
rope rotation can damage a wire rope.
To assist in determining whether or not a swivel should be
used in the lifting system, the following recommendations
should be considered. It must also be recognized that the
rotation characteristics of different types and constructions
of wire rope vary considerably. The following types and
constructions of wire rope are grouped according to their
rotation characteristics.
Group 1
Wire rope constructions having very high rotation
characteristics should not be used with a swivel under any
circumstances.
These rope constructions will rotate excessively with one
end free to rotate and the rope will unlay and distort and
be easily damaged with a loss of rope breaking force.
Blue Strand 6x19 and 6x36 Class Lang lay
All constructions of Triangular (flattened) Strand Lang Lay
Endurance Dyform 8 Lang Lay
Constructex
Group 2
Wire rope constructions having high rotation characteristics
when used in single part reeving may require a swivel in the
system to prevent rotation in certain operating conditions.
However, this should be done only when employee safety is
the issue.
These rope constructions when used in a reeving system
with one end free to rotate will have a high level of rotation.
This will cause the rope to unlay and to some degree and
distortion of the rope will occur.
Blue Strand 6x19 and 6x36—Class Regular Lay
Endurance Dyform 6 and 8 Regular Lay
Group 3a and 3b
The ropes in this Group are designed with an inner rope
that is laid in the opposite direction to the outer strands to
provide a medium resistance to rotation. Ropes with
medium rotation characteristics are used with a swivel in
single part reeving applications. However, a swivel is not
recommended for multiple part hoisting applications or in
any application where the swivel is not necessary for safety
reasons. If it is necessary to use a swivel the rope must be
operating within the design factor of 5, must not be shock
loaded and must be inspected daily by a qualified person
for distortion.
It should be noted that if a swivel is used on conjunction
with Group 3a ropes, rope service life might be reduced
due to increased internal wear between the outer strands
and the inner rope.
Group 3a Group 3b
Endurance 8RR Rotation Resistant
Endurance l9 Rotation Resistant
Endurance Dyform 18 Rotation Resistant
Group 4
Wire ropes having low rotation characteristics used in either
single or multiple part reeving may be used with a swivel.
The reason for this is that the ropes will exhibit very little, if
any, rotation when used at the proper design factor.
Application parameters such as a fleet angle may induce
turn into a wire rope that can be relieved by the use of a
swivel. However, if the application does not induce any turn
into the rope or if a swivel is not beneficial to the
performance of the rope the swivel may not be necessary.
Endurance 35 LS
Endurance Dyform34LR /PI/MAX
NOTE: When using a swivel with any wire rope, frequent
inspection of the rope is necessary. The rope
should not be shock loaded or overloaded.
This page reprinted with permission from Bridon American