Useful Information
- Danger to Personnel
- Shock Loads
- Working Loads
- Overheating
- Abrasive Conditions
- Chemical Exposure
- Raised Loads
- Destroy Bad Rope
- Avoid Rust
- Bad Combinations
- Keep It Clean
are based on tests of new and unused rope of standard construction in accordance with manufacturer's Standard Test Methods. It can be expected that strengths will decrease as soon as a rope is put into use. Because of the wide range of rope use, changes in rope conditions, exposure to the many factors affecting rope behavior, and the possibility of risk to life and property, it is impossible to cover all aspects of rope applications or to make blanket recommendations as to working loads.
are for rope in good working condition with appropriate splices, in non-critical applications and under normal service conditions. Working loads are based on a percentage of the approximate breaking strength of new and unused rope of current manufacture. For our rope products when used under normal conditions, the working load percentage is between 8% and 20% of published strengths. Normal working loads do not cover dynamic conditions such as shock loads or sustained loads, nor do they cover where life, limb, or valuable property is involved. In these cases, a lower working load must be used. A higher working load may be selected only with expert knowledge of conditions and professional estimates of risk. If the rope has been inspected and found to be in good condition and if the rope has not been subject to dynamic loading (such as sudden drops, snubs or pick-ups), excessive use, elevated temperatures, or extended periods under load. Working loads, whenever given, do not apply in such applications as towing lines, rescue ropes, life lines, safety lines, climbing ropes, or the like.
Never stand in the line of rope under strain -if rope breaks, it will recoil with considerable force.
Whenever a load is picked up, stopped, moved or swung there is an increased force due to dynamic loading. The more rapidly or suddenly such actions occur, the greater the increase will be. In extreme cases, the force put on the rope may be two, three, or even more times the normal load involved. Examples could be ropes used as a towline, picking up a load on a slack line, or using rope to stop a falling object. Dynamic effects are greater on a low elongation rope such as polyester than on a higher elongation rope such as nylon, and greater on a short rope than on a long one. Therefore, in all such applications, normal working loads as given do not apply. For dynamic loading applications involving severe exposure conditions, or for recommendations on special applications, consult the manufacturer.
Rope that is strong enough to withstand a steady pull can be broken with a sudden jerk. Be aware of all possible dynamic loading situations. Avoid them when possible and allow for strong enough rope when they cannot be avoided.
Braided rope can develop a twist when constantly used on a winch. This makes handling more difficult and the rope should be relaxed and rotated in the opposite direction to remove a twist. To avoid this condition the direction of turns over the winch should be alternated regularly.
Join rope by splicing. Knots can decrease rope strength by as much as 60 percent. Use the manufacturer's recommended splices for maximum efficiency. Other terminations can be used, but their strength loss with a particular type of rope construction should be determined, not assumed.
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Avoid using rope that shows signs of aging and wear. If in doubt, destroy the used rope. No type of visual inspection can be guaranteed to accurately determine the actual residual strength. When the fibers show wear in any given area, the rope should be re-spliced, downgraded, or replaced. Check the line regularly for frayed strands and broken yarns. A pulled strand can snag on a foreign object during rope operation. Both outer and inner rope fibers contribute to the strength of the rope. When either is worn, the rope is naturally weakened. Open the strands of the rope and look for powdered fiber, which is one sign of internal wear. A heavily used rope will often become compacted or hard which indicates reduced strength. The rope should be discarded if this condition exists.
All rope will be severely damaged if subjected to rough surfaces or sharp edges. Chocks, bitts, winches, drums and other surfaces must be kept in good condition and free of burrs and rust. Pulleys must be free to rotate and should be of proper size to avoid excessive wear.
Rope is subject to damage by chemicals. Consult the manufacturer for specific chemical exposure, such as solvents, acids, and alkalis. Consult the manufacturer for recommendations when a rope will be used where chemical exposure (either fumes or actual contact) can occur.
It might be used again by someone not aware of the hazard of the defect. This is best achieved by cutting it up into short pieces.
Rust can cause rapid loss of strength, sometimes in as short a time as one to two weeks.
The nylon line will stretch and not carry its proportionate share of the load, thus putting extra strain on the other lines.
Heat can seriously affect the strength of synthetic ropes. The temperatures at which 50 percent strength loss can occur are polypropylene- 250° F, nylon 350° F, and polyester 350° F. When using rope where the temperature exceeds these levels (or if it is too hot to hold), consult the manufacturer for recommendations as to the size and type of rope for the proposed continuous heat exposure conditions. When using ropes on a capstan or winch, care should be exercised to avoid surging while the capstan or winch head is rotating. The friction from this slippage causes localized overheating which can melt or fuse synthetic fibers, resulting in severe loss of tensile strength.
All rope should be stored clean, dry, out of direct sunlight, and away from extreme heat. It should be kept off the floor on racks to provide ventilation underneath. Never store on a concrete or dirt floor, and under no circumstances should cordage and acid or alkalis be kept in the same building. Some synthetic rope (in particular polypropylene or polyethylene) may be severely weakened by prolonged exposure to ultraviolet (UV) rays unless specifically stabilized and/or pigmented to increase UV resistance. UV degradation is indicated by discoloration and the presence of splinters and slivers on the surface of the rope.
Dirt on the surface of rope can become imbedded inside and act as an abrasive on fibers.
Persons should be warned against the serious danger of standing in line with a rope under tension. Should the rope part, it may recoil with considerable force. In all cases where any such risks are present, or if there is any question about the loads involved or the conditions of use, the working load should be substantially reduced and the rope properly inspected before every use.
(Size range: #3 to #120) Twisted, braided, baler, seine, kite, tying, garden, parcel post, and macramé.
(Size ranges, diameter: 2/32"/#2 to 12/32"/#12) Solid braid, hollow braid, diamond braid, maypole braid, flat braid, parachute cord.
(Size range, diameter: 3/16"/5mm to 5"/120mm) 3-strand twisted, 8-strand plaited, diamond braid, water ski tow rope, 12-strand braid, 16-strand braid, double braid, kern mantle, parallel core, wire lay.
Polypropylene, polyethylene, nylon, polyester, combinations of polyester and polypropylene.
Aramid: Kevlar®, Twaron®, Technora®; Ultra high molecular weight polyethylene (UHMWPE): Spectra®, high molecular weight polyethylene (HMWPE) and DSM High Performance Fibers (Dynema): Certran; Liquid crystal polymer (LCP): Vectran®; Very High Tenacity (VHT) Polyester; Polyolefin co extrusion: Polysteel®; Pet/olefin extrusion: Karat®.
is the strongest of all ropes in common use and, when stretched has a "memory" for returning to its original length. For this reason, it is best for absorbing shock loads, as is the case when lifting or towing. Nylon lasts 4-5 times longer than natural fibers because it has good abrasion resistance and is not damaged by oil or most chemicals. Like manila, nylon has good resistance to ultraviolet deterioration from sunlight (referred to as "U.V. stability").
is very close to nylon in strength when a steady force is applied. Polyester, however, stretches very little (unlike nylon) and can therefore not absorb shock loads as well as nylon. It is equally resistant to moisture and chemicals and is superior to nylon in abrasion resistance and resistance to sunlight. Polyester is the most popular general-purpose rope in the boating industry.
lightweight, polypropylene is the only rope which floats and; for this reason, is very popular for use as pool markers and water sports. Poly is affected by sunlight deterioration (more so than any other synthetic or natural fiber rope), but storing it away from direct sunlight can extend its life. Poly begins to weaken and melt at 150°F, the lowest melting point of all synthetic ropes. It is not as strong as nylon or polyester, but 2-3 times stronger than manila. Because poly is less expensive than other fibers, it is the most popular all-purpose rope for the average consumer.
especially resistant to sunlight. It is very popular for public utility construction and repair because it will not melt on contact with hot wires or equipment like synthetics do. (It will burn, however, if the temperature is very high or if the rope is in contact with the wires/equipment for an extended period). Manila holds knots firmly and stretches very little. It must be stored dry to avoid mildew. Chemicals will cause it to deteriorate.
is a hard natural fiber, but its strength is about 20% less. It, too, has excellent resistance to sunlight, little stretch, and good knot-holding ability. Sisal must be stored dry to avoid mildew and chemicals will cause it to deteriorate. Common uses include gardening, bundling, shipping, and tie downs where strength is not a critical requirement.
There are two
general categories of rope construction: twisted and braided. Coiling
three strands together in the same direction forms twisted rope. The
fibers within each of the three strands must twist in the opposite
direction as the strands in order to produce a balanced rope (one hangs
straight and resists kinking). Twisted rope must be fused and taped on
each end to prevent unraveling.
Three general categories of braided construction exist:
Diamond braid is manufactured by weaving ends of yarn
over and under, the same fashion in which the maypole dance is done. If
there is a core around which the rope is braided, it cannot be spliced.
If no core exists, the rope is called "hollow braid". The
outstanding feature of hollow braided rope is the ability to splice it
in seconds. Solid braid is very firm, round and tightly woven with a
special lock-stitch construction, which prevents unraveling when cut or
torn. Solid braided rope stands up especially well to chafing of blocks
and pulleys. This construction cannot be spliced. When the rope as well
as the core are braided, the construction is know as "braid on
braid" or "double braid". This is the strongest and most
expensive of all rope.
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