ROPE SAFETY

REGULARLY INSPECT AND DISCONTINUE USE OF ROPE WITH SUSPECT DAMAGE

  • External Abrasion: When a multifilament rope is subjected to abrasion, then the outer filaments will quickly become broken and a furry finish will develop. This furry layer will protect the yarns underneath, preventing further abrasion. If this condition does not stabilize and continues to develop, then there may be excessive abrasion that could lead to significant strength loss.
  • Internal Abrasion: The rope should be opened up so that the condition of the internal yarns can be assessed. If they show signs of abrasion, then there could be some exposure to abrasive particles or there may be inter yarn abrasion.
  • Glazing: If a rope has been subjected to excessive heat then there may be glazed or glossy spots. The glazing is caused when the yarns melt; if this has happened then the nearby yarns will also have been exposed to elevated temperatures and will have been affected. This type of damage is often seen if ropes slip on winch barrels or capstans.
  • Discoloration: This could indicate the presence of dirt that may cause internal abrasion, or it could be an indication of chemical damage. If chemical damage is suspected, then the amount that the rope has been weakened is very difficult to assess and the rope should be retired.
  • Inconsistencies: If any section of the rope is found to contain lumps, flat areas or thin bits, then this could indicate that the rope has been damaged internally. This type of damage is often caused by overloading or shock loads. Retire this rope.

SAFE WORKING LOADS

There is a great diversity of ropes, construction, materials, and usage conditions. Many factors can affect rope behavior, and the degree of risk of life and property is impossible to assess. To provide guidelines, safe working loads are calculated for rope in good condition with appropriate splices, in non-critical applications under normal working conditions. The Cordage Institute Formula for working loads is Working Load= Minimum Breaking Strength/Safety Factor.

AVOID DANGEROUS ROPE SITUATIONS

Using rope incorrectly can cause serious risk of injury to personnel and can damage property. The danger is often obvious - for example, when ropes are used to lift objects above people. When rope is under tension, if it breaks it could recoil with considerable force. If such risks are present and there is any question regarding the loads involved or the conditions of use, the working loads should be drastically reduced and the rope should be properly inspected.

ROPE WORKING LOADS WILL ALSO BE LESS FOR DYNAMICALLY LOADED ROPES

Normal working loads are not applicable when the rope is subject to dynamic loading. Dynamic loading results when load is picked up rapidly, suddenly stopped, or swung etc. In these cases, the force on the rope may be 2-3 times more than normal. Another example is picking up a tow on a slack line or using a rope to stop a falling object. Thus in all applications such as tow ropes, lifelines, safety lines, climbing ropes, etc. working loads that are given do not apply. Be aware that dynamic effects are greater on low elongation ropes such as polyester than high elongation ropes such as nylon. The dynamic affects are also greater on shorter rope than on a longer one.

TEMPERATURES CAN AFFECT TENSILE STRENGTH

Temperatures in both the high and low range can affect the tensile strength of ropes in a very dramatic way.