Chain

Equipment Operator Basic - Beginning construction equipment operators manual
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If an inspection discloses any unsatisfactory conditions in a line, see that the line is destroyed or cut into small pieces as soon as possible. This precaution prevents the defective line from being used for hoisting. CHAIN In the NCF, never use a chain when it is possible to use wire rope. The reason for this is because, unlike wire rope, chain does not have reserve strength and does not give any warning that it is about to fail; therefore, you will not be alerted of a potentially hazardous condition. Chain is better suited than wire rope for some jobs because it is more resistant to abrasion, corrosion, and heat. When chain is used as a sling, it has no flexibility and grips the load well. CHAIN GRADES It is difficult to determine the grade of some types of chains by looking at them. Most chains used by the NCF are class A chain. If you are uncertain of the class or size of a chain, ask your supervisor. CHAIN STRENGTH Before lifting with a chain, make sure the chain is free from twists and kinks. A twisted or kinked chain placed under stress could fail even when handling a light load. Additionally, ensure that the load is properly seated in the hook (not on the point) and that the chain is free from nicks or other damage. Avoid sudden jerks in lifting and lowering the load, and always consider the angle of lift with a sling chain bridle. The strength of any chain will be affected when it has been knotted, overloaded, or heated to temperatures above 500°F. HANDLING AND CARE OF CHAIN When hoisting heavy metal objects using chain for slings, you should insert padding around the sharp corners of the load to protect the chain links from being cut. Store chains in a clean, dry place where they will not be exposed to the weather. Before storage, apply a light coat of lubricant to prevent rust. Do NOT perform makeshift repairs, such as fastening links of a chain together with bolts or wire. When links become worn or damaged, cut them out of the chain, then fasten the two nearby links together with a connecting link. After the connecting link is closed, welding makes it as strong as the other links. For cutting small-sized chain links, use bolt cutters. To cut large-sized links, use a hacksaw. Inspect the chain to ensure it is maintained in a safe, operating condition. A chain used continuously for heavy loading should be inspected frequently. Chain is less reliable than manila or wire rope slings because the links may crystallize and snap without warning. Examine the chain closely link by link and look for stretch, wear, distortion, cracks, nicks, and gouges. Wear will usually be at the ends of the links where joining links rub together. If you find wear, lift each link and measure its cross section. NOTE: Remove chains from service when any link shows wear more than 25 percent of the thickness of the metal. Replace any link that shows cracks, distortion, nicks, or cuts; however, if a chain shows stretching or distortion of more than 5 percent in a five-link section, discard and destroy the entire chain. Remove chains from service when links show any signs of binding at the juncture points of the links. This condition indicates collapse in the sides of the links has occurred as a result of stretching. Before lifting with a chain, first place dunnage between the chain and the load to provide a gripping surface. For hoisting heavy metal objects with a chain, always use chafing gear around the sharp corners on the load to protect the chain links from being cut. As chafing gear, use either planks or heavy fabric. In handling rails or a number of lengths of pipe, make a round turn and place the hook around the chain, as shown in figure 13-29. Figure 13-29.—Chain sling. 13-15

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