[RIGGER’S CORNER] ASK AN EXPERT
Q. A typical chain sling assembly contains connecting links, what is the best way to inspect the connecting links during chain sling inspection to ensure the condition of the locking pins that are normally invisible?
A. Chain Slings are required by the OSHA 1910.184 and the ASME B30.9 specifi cations to undergo frequent inspections to assess the condition and ensure safety for use. A good rule of thumb for inspecting connecting links is to make sure that they swivel freely and that there is no excessive wear at the pivot points. If the connecting links do not pivot freely, there is a good chance that the sling has been overloaded and the connecting link is deformed.
Master Link (Upper End Component/Fitting)
B
Length (Reach) = A + B A
Master Coupling Link Coupling Link
Chain Coupling Link
Lower End Components (Fittings)
(a) Quadruple-Leg Bridle Sling Components
Disassembly would be the only way to actually see the pins on mechanical coupling links and hooks, but this is not practical and may not even be a recommended practice for some components. Specifi cally for mechanical coupling link pins and retainers, the inspection process would be to make sure that there doesn’t seem to be damage to the retainer, and that the pin is still engaged properly in the link. Follow these basic rules of thumb for chain sling inspection. First, ensure the sling is clean and there is enough space and lighting for inspection. Hang the sling vertically or lay the chain out on a level surface and measure from the bearing point of the master link (upper end fi tting) to the bearing point of the hook (lower end fi tting) to compare these lengths with previous recorded lengths. An increase in length may indicate that the chain has been overloaded and stretched.
76 JANUARY-FEBRUARY 2012 T en, make a link-by-link inspection and discard if:
• Wear exceeds 10% of original dimension- Campbell does off er a set of go / no-go gages for chain. T ese gages are quick and easy to use. T e gage has an opening set at the minimum thickness dimension. If the gage can go over any part of the chain, it is excessively worn and should be removed from service.
• Excessive wear, Nicks or Gouges- It is very important to examine the bearing areas (link ends), as this is a prime location for wear. T e sharpness, depth and direction of nicks and gouges are all factors to consider. Sharp or deep cuts in the chain across the chain are more serious than shallow rounded grooves running in the wire direction.
• Cracked or Broken Links or Components: T e presence of cracks or broken components on a sling are rejectable conditions.
• Bent, Twisted, or Deformed Chain or Components: chain links or other sling components that are bent, twisted or deformed are evidence that the chain sling has been overloaded or abused in some manner, and are rejectable.
• Stretched or Elongated Chain
Note that this link is longer and narrower than the original link (open arrows).
• Discoloration due to heat, Welding, Chemicals
• Corrosion or Rust
• Locked-up Condition: All components of a sling should be able to freely move and hinge.
For more information on chain sling safety, please visit Apex Tool Group, Campbell Chain at:
www.apextoolgroup.com. ❙
WIRE ROPE EXCHANGE
Photograph showing the diff erence between wear and elongation. An original chain link is shown in the center. A link showing extreme wear is on the left. Note the material reduction at the link ends (solid arrows), which increased the link’s inside length but did not change the outside length. The link on the right has been elongated 15%.
Brian Todd, Manager, Quality & Metallurgical Services for Campbell Chain, Apex Tool Group, located in York, PA.
Brian has 26 years of expertise with chain and chain fi ttings covering design, testing, quality assurance, heat treatment, manufacturing operations, metallurgy, and failure analysis. Brian serves on the ASME B30.9 subcommittee on Slings and the B30.26 subcommittee on Rigging Hardware. Brian also is the chairman of the American Society for Testing and Materials (ASTM) A01.27 subcommittee on Steel Chain, is the chairman of the National Association of Chain Manufacturers (NACM) Technical Committee, and is the chairman of the Chain Subcommittee on the Associated Wire Rope Fabricators (AWRF) Technical Committee.
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