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 TB 55-1900-232-10
c.
Cuts, contusions, etc. These also may be caused by rough or sharp surfaces. Such careless use may
cause internal as well as external damage. This may be indicated by local rupturing or loosening of the
yarns or strands. Serious cuts should be removed by cutting the damaged area out and splicing otherwise
good rope together.
d. Internal wear. Internal wear caused by repeated flexing of the line, particularly of wet nylon, and by
particles of grit which have been picked up, may be indicated by excessive loose- ness of the strands and
yarns or the presence of fuzzed or fused internal areas. Ice crystals may be a source of internal wear This
condition could result from towing m very cold weather and will most likely occur at the stern of the tug and
at the tow where the hawser is occasionally wetted, but generally exposed to the cold air
e. Repeated loading. The resistance of nylon or polyester filament line to damage due to repeated loading is
good, but a permanent elongation will occur over time in heavily-loaded ropes. If the original length of the
rope is known exactly, a check measurement made under exactly the same conditions will indicate the total
extension of the rope although some parts of the rope may escape extension. Measurement of the distance
between regularly-spaced indelible markers on the rope may help to reveal severe local permanent
elongation which may cause breaking on subsequent loading
WARNING
Surging of synthetic line under tension can cause sufficient frictional heat at the contact surfaces to
result in melting the surface of the line. The melting point of polypropylene line, for instance, is 320
F
to 340 , while the soften- ing point is around 300 . Comparable temperatures for nylon and
F
F
polyester are only moderately higher. These temperatures are quite quickly produced when a line is
surged on a winch or capstan.
f.
Heat. Heat may, in extreme cases, cause melt- ing. Any signs of this should obviously warrant rejection,
but a line may be damaged by heat without any such obvious warning. The best safeguard is proper care m
use and storage. A synthetic line should never be dried m front of a fire or stored near a stove or other
source of heat.
g. Strong sunlight Strong sunlight causes weakening of synthetic fibers, but is unlikely to penetrate beneath
the surface. Unnecessary exposure should be avoided. Solar degradation should be checked by rubbing
the surface of the line with the thumb nail. If degradation has taken place, the surface material will come off
as a powder. In addition, the surface of the line will feel dry, harsh and resinous.
C-11 SPECIAL PRECAUTIONS
WARNING
The major special precaution to be taken in the use of synthetic lines that are heavily loaded is to be
constantly alert to the danger of line snapback if it fails. Personnel must remain clear of the areas
through which the ends of a failed line may whip or snap. This is vital since the end of the broken line
can travel at speeds up to 500 mph.
CAUTION
The potential for catastrophe, resulting from the failure of a heavily-loaded synthetic line and the
sensitivity of the line to damage from rough surfaces, indicates another major precaution. That is,
when towing either alongside or stern-to-bow, with a synthetic hawser, try to keep your line completely
outboard. This can be done by shackling into a double synthetic line strap of equal size and type as
your line or into a wire rope or chain pendant. This is particularly important on the towed end, as the
conditions of those chocks, bitts, etc. are unknown. Barges usually have very rough chocks caused by
previous repetitive use of wire rope or chain.
C-5
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