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It is impossible to establish hard and fast recommendations regarding working loads due to the wide range of rope use, rope conditions, exposure to several factors affecting rope behavior, and the degree of risk to life and property involved. The tabulations for working loads are based on new, unused rope in excellent condition. These are only guidelines, even when having appropriate splices, and being used in non-critical applications and under normal conditions. If possible injury to people or damage to property exist, working loads should be reduced.
Never increase the working load beyond given guidelines without expert advice as to the conditions and risk involved. It must be determined that the rope is in excellent condition. Figures given as working loads are void if the rope has been subjected to dynamic loading, high temperatures, long periods of load, extreme stress, improper storage or improper use.
Dynamic loading occurs when rope is subjected to sudden or extreme stress such as abrupt starting or stopping of a load. The effect of dynamic loading is greater on low-elongation rope, such as polypropylene than on high-elongation rope, such as nylon. Also the effect is greater on a short rope than on a long rope.
Tensile strengths are determined from tests on new, unused rope in accordance with standard test methods of the Cordage Institute, 994 Old Eagle Schoolhouse Rd., Suite 1019, Wayne, Pennsylvania 19087.
Man made fiber ropes are stronger and more durable than natural fiber ropes. They are generally not affected by rot, mildew or most chemicals and may be stored wet or dry. The service life of synthetic exceeds that of natural fiber ropes and have proven to be more efficient and cost effective.
Nylon is strongest rope we supply. Nylon’s elasticity can absorb shock loads that would break ropes of other fibers. Resistant to abrasion, rot, petroleum products, marine growth and most chemicals, nylon rope will last many times longer than natural fiber ropes. When wet, nylon rope has approximately 15% less strength and this should be considered when selecting nylon rope.
Polyester has less stretch and elasticity than nylon plus greater resistance to ultraviolet degradation from sunlight. Other characteristics of the two fibers are practically the same.
Polypro is extensively used for many applications, polypropylene is a strong, lightweight, floating rope. Resistant to rot, mildew, petroleum products and most chemicals, polypropylene is an excellent all purpose utility rope.
Avoid sudden strain. When a working load has been used to select a rope, the load must be handled slowly and smoothly to minimize dynamic effects and avoid exceeding the provision for them.
All rope will be severely damaged if subjected to rough surfaces or sharp edges. Chocks, 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 the proper size to avoid excessive wear. Keep rope clean. Dirt and grit will act as an abrasive and will damage the rope fibers.
Never stand in line with rope under tension. Should the rope fail, it will recoil with considerable force. This could cause serious injury to persons or property anywhere in the vicinity. This danger can exist from failure of fittings within the rope’s safe working load. Check all fittings, bolts, shackles, splices and so forth before using.
Synthetic ropes can lose up to 50% of their strength when used or stored at temperatures above 140 degrees F. Slippage or surging on a capstan or winch will cause localized overheating, resulting in severe loss of tensile strength. Consult the manufacturer for recommendations as to the size and type of rope for a proposed continuous heat exposure condition.
Tying knots and creating sharp bends can decrease rope strength by as much as 50 percent. Use the manufacturer’s recommended splices and avoid sharp bends for maximum efficiency.
Most synthetic ropes are resistant to oil, gasoline, paint and most chemicals. Natural fiber ropes can be severely damaged by exposure to chemical fumes or actual contact. Consult the manufacturer for specific chemical exposure.
Synthetic ropes may be weakened by prolonged exposure to ultraviolet rays or extreme heat. Store out of direct sunlight in a cool, dry and well ventilated place. Natural fiber ropes should be kept off the floor with ventilation underneath, since they are extremely vulnerable to mildew and decay if stored wet.