Circumferences and diameter values
Linear density determines sizes of rope and cordage. The circumference and diameter values given are nominal values. When a specific circumference or diameter value is referenced, the linear density and break strengths may differ from given tables.
Working Loads
Break Strength minimums are based on data from a number of manufacturers and their products. Working loads should be determined by diving the minimum breaking strength by the design factor. Design factors set by the cordage institute vary from 5-12 for non critical applications.
Due to the sheer number of cordage constructions, materials, uses and conditions, it is not realistic to make standard recommendations as to the design factors of working loads. However, to provide some guidelines, a range of design factors and working loads are proved for rope that is designated to be new rope condition. This applies to non-critical applications, with normal service conditions. Normal service is generally considered to be use under minimal dynamic or mild static load conditions.
Design factors should only be selected with expert knowledge of use and conditions.
Critical conditions of use
High end design factors should be referenced if:
1) Loads are not accurately known.
2) Operators are not fully trained.
3) Operations and use procedures are not controlled or well defined.
4) High temperatures are present.
5) Small diameter ropes are used, (being more subject to abrasion and U.V. degradation).
6) Inspections are infrequent.
7) Chemicals are present.
8) Knots are being used, (strength can be reduced by up to 50%).
9) Rope is kept in service indefinitely.
10) Shock loads or high dynamic loads are likely.
11) Dirt or abrasion is present.
12) Tension is maintained for long periods of time.
13) If subjected to sharp radius bends, small diameter pulleys or sheaves.
14) Loss of property, death or injury may result from failure.
Critical applications may require design factors over 12. Users must determine the design factors over 12. Users must determine the design factor as they are the only ones who can assess the operating procedures and service conditions. Load applied to the rope shall not exceed working loads. If uncertain, contact a qualified engineer consultant or the manufacturer for assistance.
In all cases, working loads should be conservative. If there is any questions about the risks or loads involved, the working load should be drastically reduced. Remember, inspect rope frequently.
Dynamic Loading
When a load is moved or picked up, the force is increased due to dynamic loading.
If the actions is sudden or rapid, the greater this increase will be. In some extreme cases, the force reflects a load that may be up to three or more times the normal load. Slack should always be taken up or reduced to lessen this effect. In some dynamic cases, (falling objects for example), the design factors must be calculated to reflect the added risks. Dynamic effects are greater on shorter lengths of rope, or low elongation materials like manila or polyester as opposed to nylon for an example. Again, the design factors given reflect very modest dynamic loads or cyclic applications.
Tensile Strengths
Standard tensile strengths are reflective of new rope conditions. Recommended working loads are based on minimum tensile strengths.
CAUTION:
Never allow anyone to stand in line or along side a rope under tension. If the rope should fail, serious damage, injury or death may result from the recoil of parts, assemblies or the rope itself.
Rope will recoil in an oscillating, unpredictable path, away from its failure point with great impact. Connecting hardware and the rope itself must be selected with safety factors specific for the use and condition. Inspection of all points must be conducted to make sure that cut, worn, or frayed rope is replaced before seeing active service.
Rope will last longer if given proper care, storage and use. Please keep these important facts in mind to assure greatest service and safety.
All Line, Inc., promotes the safe use and applications of cordage products. Misuse of these products may result in damage to property, person injury or death.