4) Resistance to abrasion
Abrasion is one
of
the most common destructive conditions to which wire
rope
is
exposed.
It
will occur whenever a rope rubs against, or
is
dragged
through, any soil or other material.
It
happens whenever a rope passes around a
sheave or drum. And, it takes place internally within the rope whenever it is
loaded or bent. Abrasive action weakens the rope
by
removing metal from wires,
both inside and outside the rope.
When excessive wear occurs in a rope application, the problem could be
caused by faulty sheave alignment, incorrect sheave groove contour, an inappro-
priate fleet angle, or improper drum winding. However, there may be other caus-
es.
If
none
of
these common conditions are found to be causative factors, the
solution may be to change to a more suitable rope construction. Remember that
ropes with
larger outer wires are more abrasion resistant than ropes with small-
er outer wires and lang lay ropes are more abrasion resistant than regular lay
ropes.
(See
p.
10 -
11
for
a discussion on lang-lay rope.J
5) Resistance to crushing
Rope crnshing typically occurs in multiple layer drum spooling at the change
of
layer points and at the cross over points. At the change
of
layer point, the rope
can be wedged between the preceeding wrap on the drum and the drum flange.
This wedging creates side pressure that can distort the rope's circular shape. At
the cross over points, the rope goes from being supported by two wraps
of
rope
on the layer below to being supported at a single contact point. This doubles the
contact pressure and can crush the rope. Under very high loading conditions, the
rope may crush or flatten
around the entire circumference
of
the drum.
Items that generally increase a rope's resistance to crushing
are ropes with fewer
outer strands,
larger outer wires in strands, IWRCs instead
of
FC, regular lay
instead
of
lang lay, compaction
of
strands and compaction
of
rope.
Wire Rope Technical Board - Wire Rope Users Manual, Fourth
Edition'
61
To Next Page
Loading...
