TECHNICAL BULLETIN USE OF ROPE
RECOMMENDED WORKING LOADS (R,W,L)
R.W.L is determined by taking the average tensile strength of new rope under laboratory conditions and dividing this by a factor to determine the maximum load that should be applied to the rope.
WARNING: At least five types of load/condition combinations are not comprehended by standard safety factors, modified safety factors or any of the usual handbook treatments. Expert advice is indispensable when any substantial hazard is involved in the five' circumstances.
(1) Unusual Environmental Conditions - beyond the extremes for human exposure (including temperature, gas, liquid and solid chemicals).
(2) Impact and Shock Loads - which may generate many times the dead weight of the load.
(3) Sustained Loads - (exceeding two days) where the rope may cold flow (creep) and may also be subject to malicious mischief or accidental damage.
(4) Concealed Applications - where the rope cannot be readily inspected for wear, damage, or abuse.
(5) Use of Obviously Worn or Damaged Rope - Standard safety factors are based upon new rope and allow for only a modest amount of normal wear. In most applications, fiber rope must be considered expendable and subject to periodic replacement.
A decrease in recommended working loads must be allowed for most types of rigging, including slings, hitches and especially simple knots. Seldom do any knots have half the strength of a good splice. Many kinds of knots will pull apart without breaking the rope, particularly in some types of synthetic ropes. Still further reductions of 50 percent or more should be allowed for applications which involve the safety of children or incompetents who cannot be expected to exercise mature judgement.
Special notice concerning polyethylene and polypropylene. Polyethylene and polypropylene are subject to deterioration when exposed to direct sun light. The product should be replaced when signs of excessive deterioration is indicated by discoloration, broken filaments, raveling, etc.
CAUTION: - Never allow anyone to stand in line with or within 45o on either side of a rope under tension. Should the rope fail or other parts of the assembly fail, the recoil force could cause serious injury or damage, especially if the rope is nylon.
There is no universal agreement on what constitutes criteria for removing a rope from use and/or declaring it unsafe for use. The extent of present-day technology with synthetic ropes does not provide precise parameters where a rope can be visually inspected to determine exact extent of damage. Careful and frequent inspection of rope and a log of the length of time and conditions of use reflects prudent safety management and may provide some safeguards to protect personnel and property.
Therefore, in the interest of promoting more attention to rope inspection, the following guidelines are suggested for review and adaptation as appropriate for a given company, product or application.
GENERAL - ALL ROPES
Damaged ropes are dangerous. This list usually means replacement is necessary for safe usage.
1. Bulk of surface yarns or strands reduced by 50% or more for a linear distance equal to four or more rope diameters.
2. Cut strands.
3. Cut yarns or filaments.
4. Rope suspected of having been shock loaded.
5. Diameter reduced by 5% over new.
6. Exposure to excess temperature as specified for type of fiber.
7. Burns or melting visible for a length of over four rope diameters.
8. Abrasion on inside radius of eye.
9. Rust on nylon. (Try cleaning)
10. Oil and grease. (try cleaning)
11. Heavy surface fuzz progressive.
12. Rope used on or with sheaves, bollards, chocks or fairleads where the bending radius is less than 8 to 1.
FOR BRAIDED ROPES
13. More than four consecutive pulled cover strands (which cannot be
reincorporated into cover braid).
14. Core visible through cover, because of cover damage
(except single braids).
15. Core damage - pulled, cut, abraded, powdered, or melted strands.
16. Damage to female side of eye.
17. Rope hardened and reduced in diameter by 5% over new (sometimes called necking down).
FOR 3-STRAND ROPES
18. Damage in crossover between strands.
19. Cover yarns cut or abraded.
20. Powdering between adjacent strand contact surfaces.
21. Hockle or backturn.
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