Part N
umber
6410T0006
Version 4/23/2010
25
A wire rope that has been subjected to repeated bending over
sheaves under normal loads. This results in
fatigue breaks
in
individual wires – these breaks are square and usually in the
crown of the strands.
An example of
fatigue failure
of a wire rope subjected to heavy
loads over small sheaves. The breaks in the valleys of the strands
are caused by “stand nicking.” There may be crown breaks, too.
Here you see a single strand removed from a wire rope
subjected to “
strand nicking
.” This condition is a result of
adjacent strands rubbing against one another. While this is
normal in a rope’s operation, high loads, small sheaves, or loss
of core support can accentuate the nicking. The ultimate result
will be individual wire breaks in the valleys of the strands.
Typical evidence of wear and abuse
Sudden release of tension and the resulting rebound of rope can cause
a “
birdcage
”. These strands and wires will not be returned to their
original positions. The rope should be replaced immediately.
A typical failure of a rotary drill line with a poor cutoff practice.
These wires have been subjected to continuous
peening
, causing
fatigue type failures. A predetermined, regularly scheduled cutoff
practice can help eliminate this type of problem.
This is
localized wear
over an equalized sheave. The danger here is
that it’s invisible during the rope’s operation, and that’s why you
need to inspect this portion of an operating rope regularly. The rope
should be pulled off the sheave during inspection and bent to check
for broken wires.
This is a wire rope with a high strand – a condition in which one or
more strands are worn before adjoining strands. This is caused by
improper socketing, seizing, kinks or doglegs.
At top, you see a close-up of the concentration of wear. At bottom,
you see how it recurs every sixth strand in a 6 strand rope.
A
kinked wire rope
is shown here, it’s caused by pulling down a loop
in a slack line during handling, installation or operation. Note the
distortion of the strands and individual wires. This rope must be
replaced.
Summary of Contents for RAPID-ROLL 570
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