ROTATION
RESISTANT
ROPES
Rotation Resistant ropes are designed to resist the tendency to spin
or
rotate
under load. These ropes are used either as single part lines or in situations where
operating conditions require a rope that will resist block rotation in a multipart
system. The essential nature
of
rotation resistant rope designs impose certain
limitations on their application and necessitate special handling requirements not
encountered with other rope constructions.
There are three categories
of
Rotation Resistant ropes. They are defined
as follows:
Category 1. Stranded rope constructed in such a manner that
it
displays little or
no tendency to rotate, or
if
guided, transmits little or no torque, has at least fif-
teen outer strands and comprises an assembly
of
at least three layers
of
strands
laid helically over a center in two operations, the direction
of
lay
of
the outer
strands being opposite to that
of
the underlying layer.
Category 2. Stranded rope constructed in such a manner that it has significant
resistance to rotation, has at least ten outer strands, and comprises an assembly
of
two or more layers
of
strands laid helically over a center in two or three oper-
ations, the direction
of
lay
of
the outer strands being opposite to that
of
the
underlying layer.
Category 3. Stranded rope constructed in such a manner that it has limited resis-
tance to rotation, has no more than nine outer strands, and comprises an assembly
of
two layers
of
strands laid helically over a center in two operations, the direction
of
lay
of
the outer strands being opposite to that
of
the underlying layer.
ISO 21669 specifies a method for determining the rotational properties
of
wire
rope and guidance for use with a swivel based on this value.
8 x 19 Seale
IWRC
19x
7
8
x 25 Filler Wire
IWRC
19
x
19
Seale
18x
7
FC
35x
7
Figure 9. Cross sections
of
rotation resistant rope constructions.
35
x
19
Seale
Ropes
having
three
or
four
strands
can
also
be
designed
to
have
rotation
resistant properties.
Wire Rope Technical Board - Wire Rope Users Manual, Fourth Edition
-17
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