Document BM02wj8e5OORXvBmvxjEpGdX

26--Ropes, Chains, and Slings sling should bear a tag indicating its vertical safe load limit Allowances also are recommended for different types of hitches For example, a decrease of 25 percent in safe load limit for a single-leg verbcal sling is made when a choker hitch is used The suitable load for a basket hitch is based on the angle of the legs Special damps are used in the handling of steel plate, flanged castings, and similar shaped products. The horizontal type and the vertical type clamps have the same safe load limit as do the other bridle slings If loads that have sharp edges or sharp comers must be lifted, pads or saddles should be used to protect the ropes or chains For wire rope, the radius of bend should not be smaller than ten times the diameter of the rope For braided, cable-laid, and multi part slings, the radius should not be smaller than twenty times the diameter of the rope If the radius of bend is smaller, a choker hitch rating should be used Thimbles spliced in the ends of slings will materially reduce wear. Inspection Employees should be trained to check slings daily and whenever they may suspect damage after a lift, to report promptly any questionable conditions of the equipment or assembly A thorough inspection by a trained man should be made at least every 6 months Slings that do not meet standard require ments should be promptly withdrawn from service and either discarded or reconditioned m accordance with the recommendations of the manufacturer Chains and Chain Slings Materials Alloy steel chain has become the standard matenal for slings because it is at least twice as strong, size for size, as wiought non chain Alloy steel chain has high lesistance to abra sion and is practically immune to failuie from the cold-workuig of the metal Wrought iron chain (commonly called iron crane or dredge chain) used to be the ac cepted material for slings, hoists, cianes, 730 power shovels, and marine purposes where human life or property would be endangered by failure However, since the introduction of alloy chain in 1933, the use of wrought iron has declined steadily and has nearly dis appeared Because of this lack of commercial importance, it is not considered here Heat-treated carbon steel is sometimes used for sling chains It has high strength, high impact resistance, and good abrasion re sistance Special-purpose alloy chains are made from stainless steel, monel metal, bronze, and other materials They are designed for use where resistance to corrosive substances is required, or where other special properties are desirable Proof coil chain (also known as common or hardware chain) is used for miscellaneous purposes where failure of the chain would not endanger human life or result in senous damage to property or equipment Proof cod chain should never be used for slings Properties of alloy chain Alloy chain is produced from heat-treatable alloy steel in conformance with ASTM speci fications A391-65 Types and amounts of the alloying elements may vary according to requirements of the individual chain manu facturer Chain after heat treatment has typical mechanical properties as follows Tensile Strength Elongation 125,000 psi minimum 15 percent minimum Table 26-J shows the recommended work ing load limits, proof test loads, and the min imum breaking strengths of alloy steel chain The working load limit (safe load strength) is arrived at by dividing the breaking strength (ultimate strength) by a specified safety factor The values, shown in Table 26-J, represent the maximum loads that should ever be ap plied m direct tension to a length of allov chain All alloy chain is tested m direct tension under the proof test loads shown, prior to final inspection and shipment The data foi other types of chain may be obtained from the National Association of Chain Manufac turers' Specification No 3001 Stress on each leg of a multi-branch sling is increased appreciably when the angle be-