Synthetic Fiber Ropes
In synthetic fiber ropes the amount of strength loss due to abrasion and or flexing relates to the percentage of yarns
broken or damaged in the rope's cross-section. In virtually all rope constructions the strands have intermittent surface exposure,
usually referred to as "Crowns". Under normal conditions, abrasion is concentrated on these crowns and a rope with a smoother
surface (smaller crowns) will wear more evenly because the wear is spread over a larger area of rope surface. This has the ef-
fect of minimizing strength loss due to abrasion. When the rope is first put into service, the many and various abrasive surfaces
will cause the outer filaments of the rope to form a fuzzy surface appearance and texture. This is the result of these filaments
breaking, and this roughened surface actually forms a protective cushion and shield for the fibers underneath. This, in turn,
tends to help retard further abrasion and damage to the sub-surface fibers. This condition should stabilize, not progress. If the
surface roughness increases, excessive abrasion is taking place and strength is being lost. Abrasion may occur between the
yarns and strands due to cyclic tensioning at high loads causing internal fuzzing or powdering. Some internal fuzzing is normal
and should be added to the surface abrasion when estimating total fiber wear.
Friction Burns (Melting)
Friction of fiber ropes under high tension or rendering over bitts, capstans or winches can generate enough heat to melt
or fuse together the outer fibers. This type of melting can lead to serious strength loss.
Visual inspection can readily detect this melting or fusion and unless the damage is obviously gross, it must be emphas-
ized that no type of visual inspection can be guaranteed to accurately and precisely determine actual residual strength. Heat
damage is evident when the rope surface becomes glazed and shiny due to a film of melted fiber on its surface. Ropes that ex-
hibit fusing below the outermost layer of fiber must be considered highly suspect and must be examined closely to determine the
extent of damage. Fibers or strands adjacent to the fused area will appear to have the same appearance of any other undam-
aged fiber. They may in reality have been located very close to a melted or fused area and, being this close, may have been
subjected to heat above their critical temperature but still have not reached their melting temperature. For all practical purposes,
this type of damage represents an extremely difficult decision for the inspector. If there exists any doubt at all, the rope should
be discarded, especially if fusing or melting has affected more than 20% of the total fiber in the rope cross section.
Critical Temperatures (50% strength loss, short-term exposure*)
Spectra (Amsteel/Amsteel Blue).....................150 Degree F
Nylon
..........................................................350 Degree F
Polypropylene..................................................150 Degree F
Polyester..........................................................390 Degree F
Manila
180 Degree F
* Lengthy exposure or storage at elevated temperatures will reduce strength permanently.
Cut Strands
Estimating the strength loss from one or more cut strands, in principal, is the same as estimating strength loss as a res-
ult of abrasion. Estimating the percentage of intact and undamaged fiber will give you a reliable estimate of the rope's remaining
strength provided there is no other cause of strength loss. In Spectron 12 Plus, a single cut strand represents approximately
8.5% of the rope strength; two adjacent cut strands represents approximately 17% of the total rope strength. If more than two
adjacent strands are cut the rope should be considered for immediate replacement.
Pulled Strands
Braided rope, will occasionally experience a pulled strand. Most often this occurs while the rope has little or no load (re-
laxed). Every effort should be made to reincorporate a pulled strand back into the rope proper by hand working the loop back
into the body of the rope. If this is done, strength loss is minimal; if left unattended a pulled strand presents additional snagging
hazard.
In the event this is not possible, the loop should be cut off and the strand ends re-incorporated into the body of the rope. A tight
whipping at this point would provide added protection. A percentage of strength loss will occur which is proportional to the per-
centage of fiber in the cut strand.
Operation & Maintenance Manual
Model 1570-B Puller
09/2010
Page 10
