Figure 6-18. - Determination of single-basket hitch sting capacity.
bulge on the side or end of the link. Chain size refers to the diameter, in inches, of the wire used to fabricate the chain.
In the NCF, never use a chain when it is possible to use wire rope. Chain does not give any warning that it is about to fail. Wire rope, on the other hand, fails a strand at a time, giving you warning before failure actually occurs.
NOTE: Although chain gives no warning of failure, it is better suited than wire rope for some jobs. Chain is more resistant to abrasion, corrosion, and heat. Additionally, use chains to lift heavy objects with sharp edges that could cut wire or are hot. When chain is used as a sling, it has little flexibility but grips the load well.
First, you must be aware that chains normally stretch under excessive loading and individual links will be bent slightly. Therefore, bent links are a warning that the chain has been overloaded and may fail suddenly under load. 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 is negatively affected when it has been knotted, overloaded, or heated to temperatures above 500°F.
Figure 6-19. - Determination of double-basket hitch sling capacity.Continue Reading