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Alloy chain possesses excellent ductile properties typical of most rigging hardware. The links actually stretch a little when overloaded. This deformation is a warning sign, cautioning the user that the chain has been overloaded and its capacity reduced. Deformed chains must be removed from service. Chains that are not made of alloy steel don't have good ductile properties. they can fail without warning. For this reason, non-alloy chains are prohibited fro overhead hoisting. The disadvantage of chain is that it is only as strong as its weakest link. When wires break in a wire rope sling under load, it doesn't necessarily translate into an accident. But when one link in a chain fails, the load will come down. While regular inspection is essential to all rigging operations, it is especially critical where chain slings are being used.
Tackle
Regulations, Part IV, Cargo Gear, 21(8): All chains......and
all rings, hooks, shackles, swivels and pulley blocks shall be
inspected by a competent person immediately before each occasion on
which they are used in hoisting or lowering, unless they have been
inspected within the preceding three months. |
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A Few Tips: - Hose off the deck where you will be working to remove as much grit and abrasive material as possible. - You can use Crack Detector spray. - Inspect every link, including joining apparatus. - Inspect for inner link wear and wear on outside of the link barrels. Manufacturers publish tables of allowable wear for various link sizes. - Check for nicks and gouges that may cause stress concentrations and weaken links. - Renew any tags or stamps that identify the chain. - Ensure the Hammer-Locks move freely and that they are not overly worn. Lubricate them. - This is also an ideal opportunity to take photos of, or sketch, anything unusual. This may be of use in the future. - Make notes of what you found, where you found it and what, if anything, you did about it. - If you replace a Master Link , Hammer Lock, Chain, Hook or any other part, ensure the new part is certified and identified. Better yet, send the entire unit to a test facility for recertification. - If you find a chain that requires recertification, tag it as such and set it aside. Do not use it until it has been recertified. - If you find a chain that requires disposal, chop it up and dispose of it. Do not keep it.
- If in doubt, dispose of the chain.
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Refer to the Construction Safety Association of Ontario
"Rigging Manual", Chapter 3, Chain. |
