TM5-3810-305-10
3. Reduction in rope diameter: Any marked
reduction in rope diameter indicates degrada-
tion. Such reduction may be attributed to:
a. Excessive external abrasion.
b. Internal or external corrosion.
c. Loosening or tightening of rope lay.
d. Inner wire breakage.
e. Rope stretch.
f. Ironing or milking of strands.
In the past, whether or not a rope was allowed
to remain in service depended to a great
extent on the rope’s diameter at the time of
inspection. Currently this practice has under-
gone significant modification.
Previously, a decrease in the rope’s diameter
was compared with published standards of
minimum diameters. The amount of change
in diameter is, of course, useful in assessing a
rope’s condition. But, comparing this figure
with a fixed set of values is, for the most part,
useless. These long-accepted standards are
not, in themselves, of any serious significance
since they do not take into account such
factors as:
a. Variations in compressibility between
IWRC and Fiber Core.
b. Differences in the amount of reduction in
diameter from abrasive wear, or from core
compression, or a combination of both.
c. The actual original diameter of the rope
rather than its nominal value.
As a matter of fact, all ropes will show a sig-
nificant reduction in diameter when a load is
applied. Therefore, a rope manufactured
close to its nominal size may, when it is
subjected to loading, undergo a greater reduc-
tion in diameter than that stipulated in the
minimum diameter table. Yet, under these
circumstances, the rope would be declared
unsafe although it may, in actuality, be safe.
As an example of the possible error at the
other extreme, we can take the case of a rope
manufactured near the upper limits of allow-
able size. If the diameter has reached a
reduction to nominal or slightly below that,
the tables would show this rope to be safe.
But it should, perhaps, be removed.
Today, evaluations of the rope diameter are
first predicated on a comparison of the orig-
inal diameter - when new and subjected to a
known load - with the current reading under
like circumstances. Periodically, throughout
the life of the rope, the actual diameter should
be recorded when the rope is under equivalent
loading and in the same operating section.
This procedure, if followed carefully, reveals
a common rope characteristic: after an initial
reduction, the diameter soon stabilizes. Later,
there will be a continuous, albeit small,
decrease in diameter throughout its life.
Core deterioration, when it occurs, is revealed
by a more rapid reduction in diameter and
when observed it is time for removal.
Deciding whether or not a rope is safe is not
always a simple matter. A number of differ-
ent but interrelated conditions must be evalu-
ated. It would be dangerously unwise for an
inspector to declare a rope safe for continued
service simply because its diameter had not
reached the minimum arbitrarily established
in a table if, at the same time, other observa-
tions lead to an opposite conclusion.
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