A Wire Rope Is a "Machine"
With
Many
Moving
Parts
A wire rope is a machine, by dictionary
definition:
"An
assemblage
of
parts
..
.that
transmit forces, motion, and energy one
to
another
in
some
predetermined
manner
and to some desired end."
A typical wire rope may contain dozens -
even hundreds -
of
individual wires which
are fonned and fabricated to operate at
dose
bearing tolerances one to another. When a
wire rope bends, each
of
its many wires
slides and adjusts
in
the bend
to
accommo-
date the difference
in
length between the
inside
and
the
outside
of
the
bend.
The
sharper the bend, the greater the movement.
Every wire rope has three basic compo-
nents:
(l)
The
wires
which
form
the
strands
and
collectively
provide
rope
strength; (2)
The
strands, which are laid
helically
around
the
core;
and,
(3)
The
core,
which
forms
a
foundation
for the
strands.
The
core
may
be
either
a fiber
rope,
an
Independent
Wire
Rope
Core
(IWRC). which
is
actually a smaller wire
rope,
or a strand similar to the outer
strd.l1ds
of
the rope; only an IWRC
or
strand core
contributes
strength
to
the
rope;
and an
IWRC normally provides only 7
1/1%
of
the
wire rope's Nominal Strength.
TI1e
greatest differences in wire ropes are
found
in
the
strands,
which
may
vary
widely
in
the pattern and number
of
wires
which
are laid together.
The
wires
of
a rope may be made
of
various
metals, including steel, iron, stainless steel,
monel,
and bronze. TIle material
of
which
the wires
are made is the plimary determi-
nant of rope strength. By
far the most widely
used metal is high-carbon steel.
Carbon steel wire ropes
come
in
various
Grades. The term
"Grade" is used to desig-
nate
the
Nominal
Strength
of
the
wire
rope.
The
most common rope Grades are
Traction
Steel
(TS),
Plow
Steel
(PS),
Improved
Plow
Steel
(IPS),
Extra
Improved
Plow
Steel
(EIPS),
and Extra
Extra Improved
Plow Steel (EEIPS).
CENTER
WIRE
One cannot determine the Grade
of
a wire
rope by its feel
or
appearance. To properly
evaluate a rope system you must obtain the
Grade
from your
employer
or
wire rope
supplier.
This publication was produced by the Wire Rope Technical Board,
the technical information organization
of
the United States wire rope industry.
For further information, contact: wrtb@usaJ1et
©
1993,
WRTB
AU
rights reserved.
Form 293
Printed in U
.SA
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