Alloy chain slings are one of the most durable riggings out there. They are used in crane rigging for lifting loads, in heavy goods transport to tie down the loads, and in industries like power, manufacturing, mining, and petroleum, among others.

These slings are available in different grades and usage specifications. As they are robust, it is not uncommon to use alloy chain slings for more than a decade or even 20-30 years. However, they do require frequent inspection and proper care to ensure the safety of rigging operators.

A. How Often Should Chain Slings Be Inspected?

Regular chain sling inspection is critical to ensure safety. Usually, there are three types of chain inspections that a qualified person should perform.

  • Initial Inspection

As the name suggests, you need to perform this chain inspection after you have bought a new alloy chain sling. You need to check everything from the identification tags to rated capacity and specifications. A visual link-by-link inspection can also help to identify any manufacturing defects.

  • Frequent Inspection

You can ask a competent person on your rigging staff, preferably someone with years of industry experience, to conduct frequent inspection. Make sure the person follows a standardized alloy chain sling inspection procedure to check all elements of the sling for damages or deformities. You can plan for a daily inspection. However, it better to inspect the chain sling before each job.

  • Periodic Inspection

A certified person, usually a rigging inspector, will perform the periodic chain sling inspection. According to American Society of Mechanical Engineers (ASME ), you have to consider factors like the frequency of use, severity of work conditions, nature of lifting, and the service life of chain slings used in similar applications to determine how frequently you need periodic inspection.

  • Normal Service – Once a year
  • Severe Service – Once a quarter or a month
  • Special Service – As recommended by a certified expert

B. Chain Sling Inspection Checklist

You will need to make a list of things you have to check before use. This chain sling inspection checklist will make sure you don’t miss any vital elements during the inspection.

  • Missing or illegible identification tags
  • Cracks or breaks
  • Excessive wear and tear
  • Nicks and gouges
  • Elongated or stretched chain links or components
  • Potential heat damage
  • Excessive pitting or corrosion
  • Lack of free hinging of the chain or its components
  • Weld splatter
  • Inspect hooks as per ASME B30.10 rules
  • Inspect rigging hardware as per ASME B30.26 rules
  • Any other visible damage that warrants immediate removal of chain sling

C. Understanding the Alloy Chain Sling Inspection Procedure

If you want to ensure the highest level of safety on rigging jobs, you need to develop an in-depth alloy chain sling inspection procedure. Although it may take a while to set up the process, it will be worth the efforts.

Usually, a comprehensive inspection process includes the following five steps.

1. Twisting and Bending

When using alloy chain slings, you need to adjust and use them as per manufacturer’s recommendations. You must avoid twisting and bending at all costs. When evaluating a chain sling, manufacturers apply loads in a pure tensile link-end-to-link-end fashion and rate the sling accordingly.

However, if you don’t use proper padding or the recommended D/d ratio for the chain, the links will be twisted and bent, altering the link stress. Once the link stress changes, the sling becomes prone to failure during rigging. The ASME B30.9 standards (released in 2018) have adopted the reductions in working load limits based on the tests by the National Association of Chain Manufacturers (NACM).

The following chart describes the reduction (percentage) in working load limits based on the D/d ratio for alloy chains rigged around an edge or a corner. Make sure to follow these recommendations when using alloy chain slings. If you find any twisted or bent links during your alloy chain sling inspection, discontinue using them immediately.

 

D/d Ratio
Rated capacity (%)
Less than 2
Not recommended
3
60
4
70
5
80
6 and above
100

Source

2. Nicks and Gouges

The next step is to look for nicks and gouges. The outer and inner sides of chain links often develop nicks and gouges due to friction and stress. However, the chain links are designed to protect their tensile stress areas from the damage caused by external factors.

The tensile stress areas are present on the outside of a chain link body and also the insides of the straight barrels. When interconnected, chain links protect tensile stress areas on the outside of a link body. On the other hand, the design itself protects tensile stress areas insides of the straight barrels of a chain link.

Unfortunately, when nicks or gouges develop in these areas, especially perpendicular to the direction of stress, they can compromise your safety. In other words, the location of a nick or gouge will determine how harmful it is. For example, a deep transverse nick in the area of maximum tensile stress is more harmful than a longitudinal nick in the area of compressive stress.

Depending on the location of the nick, filling out a nick or gouge can work. Although the resulting cross-sectional area will be smaller, the chain link will be stronger as filling out will remove the increased stress levels. However, you will need to refer to the Wear Allowances Table when making these repairs. If your alloy chain sling inspection reveals that nick or gouge is too deep, you need to replace the sling immediately.

3. Wear and Corrosion

Looking for wear and corrosion is an essential step in the alloy chain sling inspection procedure. The corrosion and wear will weaken the chain links, which results in unsafe lifting and rigging conditions. Using such alloy chain slings can lead to potentially fatal accidents.

a) Wear and Tear

Physical contact with the load and interlinked chain links can result in wear and tear over time. For example, dragging chains under the load can cause significant wear and tear.

The two primary areas prone to wear and tear are –

  • The bearing points where chain links are interconnected
  • The outer surface of the straight side barrels which come in contact with the load or foreign objects

b) Corrosion

Usually, when the alloy chain sling gets exposed to water, moisture, and harsh chemicals, corrosion will occur. Although you can take precautions to avoid corrosion, when you use chain links in harsh environments, it is challenging to prevent both wear and corrosion.

Visual chain inspection is probably the best way to identify the extent of wear and corrosion. You can continue to use the chain if the damage is not small.

You can do the following –

  • Use a Caliper to measure the diameter of the worn-out section. If the diameter is smaller than the recommended size, remove the chain sling from use immediately.
  • If the corrosion is minimal, you can clean and oil the chain before using it. However, if you see pitting after oiling, stop using the chain.

4. Stretch and Chain Elongation

Prolonged use will also cause chain links to stretch, especially when you overload chains frequently. Careful visual alloy chain sling inspection can help you identify dangerously elongated chain links.

However, inspecting the overall chain length is usually not enough because it often fails to identify considerable elongation in a few links. As a result, you need to conduct a link-by-link inspection. The most common sign of stretch is the loss of clearance or binding at the points where links interconnect.

Most alloy chain slings have an acceptable stretch limit of up to 20%. However, you should check with your manufacturer to be 100% sure. If the elongation is large, remove the chain from use immediately. To lower the risk of chain elongation, you will also need to prevent overloading.

5. Refer to the OSHA Chain Sling Inspection Guidelines

First published in 1975, the OSHA Chain Sling Inspection section offers insightful guidelines for alloy chain sling inspection procedures. As OSHA inspectors often refer to these guidelines, following them during your sling inspection can help a lot. You will need to refer to the Code of Federal Regulations (29 CFR 1910.184), available on the OHSA website, among other online resources.

Conclusion

Alloy chain slings are essential for virtually all heavy-duty riggings, especially in harsh environments. That’s why it is necessary to ensure proper care and follow chain sling inspection requirements to ensure safety. Hopefully, this post will help you understand how to perform chain inspection and how frequently you should do it. If you need help inspecting alloy chain slings, reach out to our team at Holloway Houston Inc. Our experts will help you ensure legal compliance and safety effortlessly.