SELECT BEST ROPE FOR THE JOB. Economy as well as service depend on the right size and quality for the work. Allow a safety factor of at least five to determine safe working load for new rope. As rope ages, the safety factor should be increased.
INSPECTION. New rope should be thoroughly inspected throughout its entire length before it is placed in service to determine that no part of it is damaged or defective. After it is placed in service, rope should be inspected at least every thirty days under ordinary circumstances; more often if it is used to support scaffolding or other supports upon which men work. If it is exposed to acids or caustics, it should be inspected daily. Inspection should include examination of the entire length of rope for wear, abrasion, broken or cut fibers, displacement of yarns or strands, discoloration or rotting. To inspect the inner fibers, the rope should be untwisted in several places to make sure the inside yarns are bright, clear and unspotted. The specification tables show breaking strengths and safe working loads. Rope loaded to over 75% of its breaking strength will be permanently injured. Damage from this cause may be detected by examining the inside threads which will be broken to an extent governed by the amount of the overload. Such damage may also be determined by the reduced diameter of the weakened section of the rope. Care should be taken to prevent kinking a rope. Even a moderate strain may over-stress the fibers at the point of the bend, producing a serious defect and one that may be difficult to locate.
KINKS CAUSE ROPE FAILURE. Prevent kinks which cause permanent damage and weakening of the rope. If kinks should form, or if rope is continually twisted in one direction, as over a winch, remove kinks or restore balance in the rope by throwing in twist in opposite direction.
SPLICE ROPE FOR PERMANENCE. A splice is stronger than a knot. The strongest way to join two ropes, or to make a sling or endless rope, is to splice it correctly. Even the most efficient knots will reduce rope strength to as much as 50%, while a carefully made splice may have up to 95% of the strength of the rope being spliced. A short splice gives the strongest coupling however, it doubles the rope size and is not suitable where rope must run through pulleys or sheaves on a block. For such purposes, a long splice, with up to 90% strength efficiency, is used.
ROPE SLINGS. Small angles increase rope stress. Allow for sling angles. The breaking strength of rope is based on direct pull along a single length of rope. When slings, using two or more legs to carry the load, are properly employed, the rope's safe working load is substantially increased. However, the load factor on each leg of the sling is greatly increased as the sling angle becomes smaller. Therefore, the use of slings requires certain precautions as well as a knowledge of safe working loads permissible. For best results, sling angles should never be more than 90 degrees - rarely less than 45 degrees.
AVOID SUDDEN STRAINS. Jerking or sudden strain may cause failure of a rope normally strong enough to handle the load safety. A steady, even pull will assure full strength from rope. This is especially important when using slings or tackle which may multiply strain and power.