One of the most important parts of an electric chain hoist to inspect carefully is the lifting chain. Most hoist lifting chains are “case hardened”, meaning that the surface coating of the chain is very hard while the inner metal of the chain is much softer and less resistant to wear. Once the chain has worn through the “case” material, the chain can wear through to failure very quickly. That is why the daily/shift inspection and detailed documented monthly inspection of hoist chains is so critical.
The lifting chain may be single fall (1 parts) or multi fall depending on the capacity and reeving requirement. In a single fall application, the chain only goes over the hoist lifting wheel or sprocket. In multi fall applications, the chain also goes through lower chain sprockets as well. The more pivoting of the chain under load, the more opportunity for wear.
Improper lubrication of the load chain is the biggest contributor to rapid chain wear. It does not take a tremendous number of cycles of bare chan over the bare chain to wear through the very thin “case” hardening.
Hoist Chain Inspection
Prior to inspecting the chain, clean off heavy dirt and grease that impedes proper visual inspection
If the chain is dirty, it may be difficult to inspect. Therefore, it is important to make sure the chain is clean, so you can see any damage. Inspect as much chain as you can. On hoists hung from overhead trolleys and beams, you will not be able to inspect the entire length of the chain during a daily/shift inspection. Checking the entire length of the chain will be part of a documented inspection monthly or periodic inspection.
When conducting the hoist chain inspection, you should look for:
1) Inner link wear, gouges, nicks, and twists: Inner link wear is difficult to see without moving links and is covered in detail during the Periodic Inspection. However, if something looks wrong, have someone check the chain in more detail.
2) Bent or broken links
3) Chemical damage or corrosion
4) Stretch: Hoist chain does not stretch like lifting chain. it can be difficult to determine if the chain is stretched without measuring it. Full measurements are completed during the Periodic Inspection. However, if something looks wrong or out of proportion, take the time to measure the links. Chain sizes vary from hoist to hoist so you will need to refer to the product’s O&M manual to verify chain measurements.
Finally, check for proper lubrication.
Lubrication is important to extend the life of the chain and the hoist. It helps wear and helps the chain articulate properly. After you clean it for the inspection, make sure it is properly lubricated.
Here are some extreme examples of chain damage. Often wear will not be this apparent.
Important note to the stretched links image:
Hoist chain is not designed to stretch.
If you see anything of concern, take the hoist out of service and bring it to the attention of a trained hoist inspector for further evaluation.
For additional assistance, please call your inspection experts at CRANE 1.