All chains used regularly should be thoroughly inspected link-by-link at least once per month. Under no circumstances should a chain be used for hoisting unless it has been closely examined for defects or wear.
Whenever a chain is subjected to shock or impact loads, it must be immediately inspected before being put back into service
Every chain should carry a small metal identification tag bearing a serial number and its safe working load. A log book should also be kept for the chain, identifying its characteristics and setting up an inspection schedule.
When inspecting chain, closely examine each link. One bad link can cause the chain to fail.
- Look for elongated or stretched links. When the links are severely stretched, they tend to close up. Thus links that bind or a chain that will not hang perfectly straight may indicate stretch.
- Elongation should be determined by measuring with a caliper all new chains in sections of 1 to 3 feet and re-measuring them during inspection. If the inspection reveals a stretch of more than 3%, take the chain out of service.
- Look for bent, twisted or damaged links that often occur when the sling is used to lift a load having unprotected sharp edges.
- Look for cracked links. The presence of a crack of any size means the chain is unsafe and must be removed from service.
- Look for gouges, chips, scores or cuts in each link. If they are deep or large in area, the chain should be removed from service.
- Look for small dents, peen marks and bright polished surfaces on the links. These usually indicate that the chain has been work hardened or fatigued.
- Look for lifted fins at welds. They are evidence of severe over-loading, and the chain should be destroyed.
- Look for severe corrosion resulting in measurable material loss or severe pitting.
- Be particularly careful in determining link wear at the point where the links bear on each other. A caliper should be used for measuring and the degree of wear at the must worn link must be determined during the inspection.
