The following is a fairly comprehensive listing of critical inspection
factors. It is not, however, presented as a substitute
for an experienced inspector. It is rather a user’s guide
to the accepted standards by which ropes must be judged.
Rope abrades when it moves through an abrasive me rum
or over rums an sheaves. Most standards require that rope
is to be removed if the outer wire wear exceeds 1/3 of the
original outer wire diameter. This is not easy to determine
and discovery relies upon the experience gained by the inspector
in measuring wire diameters of discarded ropes.
2. Rope stretch
All ropes will stretch when loads are initially applied.
As a rope degrades from wear, fatigue, etc. (excluding accidental
damage) , continued application of a load of constant
magnitude will produce incorrect varying amounts of
Phase 1. Initial stretch, during the early (beginning) period
of rope service, caused by the rope adjustments to operating
conditions (constructional stretch).
Phase 2. Following break-in, there is a long period—the
greatest part of the rope’s service life-during which a slight
increase in stretch takes place over an extended time. This
results from normal wear, fatigue, etc. On the plotted curve—
stretch vs. time—this portion would almost be a horizontal
straight line inclined slightly upward from its initial level.
Phase 3. Thereafter, the stretch occurs at a quicker rate.
This means that the rope has reached the point of rapid
degradation; a result of prolonged\subjection to abrasive
wear, fatigue, etc. This second upturn of the curve is a warning
indicating that the rope should soon be removed.
3. Reduction in rope diameter
Any marked reduction in rope diameter indicates degradation.
Such reduction may be attributed to:
- excessive external abrasion
- internal or external corrosion
- loosening or tightening of rope lay
- inner wire breakage
- rope stretch
- 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 undergone
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 can be misleading. These long-accepted
minimums are not, in themselves, of any serious significance
since they do not take into account such factors as: 1) variations
in compressibility between IWRC and Fiber Core; 2)
differences in the amount of reduction in diameter from abrasive
wear, or from core compression, or a combination of
both; and 3) the actual original diameter of the rope rather
than its nominal value
As a matter of fact, all ropes will show a significant reduction
in diameter when a load is applied. Therefore, a rope
manufactured close to its nominal size may, when it is subjected
to loading, be reduced to a smaller 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 allowable 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 original 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.