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Inspection Guidelines for Plasma® Synthetic 4x4 Winch Lines.
courtesy of Ruftraks UK Ltd and
Prepared in association with Puget Sound Ropes.
Plasma
synthetic winch lines were introduced to the off-road vehicle markets in the
late 1990’s, and have
rapidly
become a must-have accessory for hard-core
off-road enthusiasts.
Based on experience gained during off-road challenges and adventures since their
introduction, several
specific
end-use conditions and hazards have been identified which can be harmful to
Plasma ropes.
The presence of these
conditions can best be determined by periodic inspection of the lines and the
hardware
on which it operates.
This guidance document presents recommendations for periodic inspection by the
end user. These guidelines are
aimed particularly at the serious off-road driver, who will be using their tow
cables every week if not daily.
Conditions to be avoided in
Plasma Lines
There are three areas where
close attention needs to be paid to Plasma lines. Below are descriptions of
these
conditions and likely signs of their presence.
1. Repeated lateral
abrasion against sharp edges is to be avoided. While HMPE is one of the most
cut-resistant
polymers available, hard rough-surfaced materials (rocks, sharp metal) can prove
to be stronger than Plasma in a
long-duration abrasion event. Signs of excess abrasion include strand
pull-outs, heavy chafing, and/or cut strands
in a single area. It should be noted that normal light fuzzing of the Plasma
rope surface is to be expected in
normal use. This light fuzzing does not reduce the rated strength of the line,
and actually creates a protective
layer on the rope that helps to prevent further damage. External protection
against chafing (e.g. woven chafe
sleeves or socks) should always be used where the rope will contact sharp or
abrasive objects.
2. Plasma begins to lose
strength above about 70 ºC, and has a zero-strength temperature around 150 ºC.
If the winch is overheated by extreme use (e.g. extensive backing down or
lowering under load) then the
heat
generated by the friction brake inside the
winch
drum can transfer heat to the rope and cause
it to be
degraded. Signs
of high temperature damage include
melted areas, fused (inseparable) strands, and significantly
reduced diameter.
Using the winch in accordance with
the manufacturer’s recommendations should cause no
overheating of the rope. It
should be noted that sometimes
the
rope remaining on the winch drum might
appear to be fused, melted or deformed.
However, this is not caused
by
overheating but is a result of
compressive flow and set of the rope coating.
This can occur when the winch line
is
heavily loaded while there
are two or more layers of rope on the drum. If
necessary, flexing the rope by hand to
separate the strands can
soften up this stiff section, a process that causes no
damage to the fibers.
3. Plasma lines can lose
strength if overstrained. Overstraining is the result of exceeding the
recommended
working load limit, whether instantaneously (by transient peak loads during
dynamic loading events) or for an
extended time period (by overworking the winch/rope system). The working load
limit of the line (the minimum
breaking load decreased by a design factor) should be chosen based on experience
in the end use, along with
consultation with the winch and rope supplier if necessary. Loading at high
angles or around small bends can
also cause excessive strain, for example in a choker configuration. Signs of
overstraining can be subtle but
include localized thinning and elongation, and loss in flexibility (for example
the rope becomes rigid).
Inspection Guidelines
for the Rope / Winch System:
Below are some suggestions
for inspecting Plasma lines and their winching mechanisms for the above damage
conditions. Each end user should develop their own method of routinely
inspecting these lines for damage prior
to each use. The method and frequency of inspection will depend on the end
users experience and usage level.
1. Pull the rope out from
the winch as you walk to the nearest tree or other fixed object and secure the
end
of the line using a suitable method. If you have not yet done so, put a
brightly colored mark on the line at a
point just beyond where the rope is secured. This will be a reference mark for
future measurements, and should
be made as permanent as possible (one suggestion is to tie a bright ribbon
through one or two strands of the rope).
2. As you are walking back from the tree, visually inspect
the rope for any signs of abrasion, localized thinning,
or melting. Signs to look for (as noted above) include pulled strands, heavy
fuzz, stiff regions, regions of
inseparable strands, and thinned areas. This inspection should include the
portion of the line wrapped around
the tree, and the portion of the line between the tree and the winch. Make a
note of any damage
areas.
3. Pull the rope out from
the winch, visually inspecting it as you do so, until the minimum recommended
line
length remains on the winch drum. (Alternately, if you primarily use the front
portion of the line, only pull
out the most commonly used length.) If you have not already done so, put a
bright mark on the line at the point
where the line now exits the winch. This will be a reference mark for future
measurements, and should be
mounted securely, as in step 1 above.
4. Carefully inspect the
winch drum, winch flanges, and any winding aids, rope guides, or running
surfaces
where the rope comes in contact with metal portions of the vehicle. Feel these
surfaces by hand to ensure they
are free from nicks, burrs, rust, or sharp edges. All running surfaces should
be rounded to at least the same
diameter as the rope. Check rolling surfaces to make sure they turn freely.
5. Check the rope that
remains on the winch drum for signs of melting, thermal fusing, or thinning.
(Coating
flow has a similar appearance to fusing – see above comments.) Check that the
drum surface is smooth.
6. Using the vehicle and
the winch, put a small (less than 10% of break load) but repeatable load on the
line.
In subsequent inspections a similar load should be applied again, so determine a
method that will give
approximately the same line load each time.
7.
Walk back to the tree, again visually inspecting the line as you go (again, note
any damage areas). Using a
flexible tape measure, measure the length between reference marks. Write down
this reference length and
compare it to previous measurements.
8. Return to the vehicle,
remove the load on the line, disconnect the line from the tree and rewind onto
the vehicle.
9. Keep a record of the
line reference length as well as any damage areas and their approximate
locations
relative
to one or both reference marks. Future inspections should be used to monitor
minor damage areas
for signs of growth.
Inspection Frequency
The end user should
determine the frequency of rope inspections. For heavy off road enthusiasts,
the rope should be
carefully inspected prior to each application. The user should also perform a
quick visual inspection (without length
measurement) prior to any use of the rope, for example just after connecting to
an anchor point while walking back
to the vehicle.
Rope Disposition:
Ropes that show severe
damage should be replaced, repaired (damaged areas cut out and butt-spliced),
end-for-ended,
or down-rated to other applications. Examples of severe damage in Plasma rope
include (but are not limited to):
a.
two or more strands severed within a 0.5 meter segment
b. thermally fused segment
that is no longer flexible (strands
not separable)
c. localized diameter
reduction of more than 20%
d. strands melted through
on one side, inseparable strands
e. rope that has
lengthened (between reference marks) by more
than 10%
Each end user should
determine through experience which signs of damage are more indicative of
impending failure.
(For example, the critical damage mode of a rope that fails in service might be
identified if the location of the
break can be traced to damage noted in a prior inspection.)
© copyright: First Four Off
Road 2003
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