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Safety is of the utmost importance whenever an operation requires lifting or securing a heavy object. In many cases, you will use a rigging chain. However, you need to use one with a suitable grade. Otherwise, you, your employees, and passersby are at risk of severe injury and possibly death.
Read on for a comprehensive explanation of chain grades and their applications.
Grades are the standard method for showing a chain’s tensile strength or breaking strength. The higher the grade, the stronger it is. The equation for calculating it is as follows:
Chain grade = maximum tensile force in Newtons/area of two cross-sections of a single chain link
or
Chain grade = N/mm2
Keep in mind that a chain’s grade is not equal to its working load limit. That’s determined by a combination of the grade and the width of the links. This is why chains of the same grade can differ in working load limits by several thousand pounds and why a lower-grade chain can carry more than a thinner, higher-grade chain.
There are currently seven chain grades used in rigging and lifting. The most common of them are 30, 43, 70, 80, and 100.
Grade 50 and 63 stainless steel chains are approved for overhead lifting, but they’re not used as often since grade 80 and 100 alloy steel chains are much stronger. There are also grade 120 chains, but they’re relatively new and hard to find.
Carbon steel chains consist of grades 30, 43, and 70 chains. They are for general use, such as tying down heavy cargo, container securement, and towing. Take a look at how they differ:
Working load limit: 1,300 - 6,900 lbs
Grade 30 chains are economical, general-purpose chains used in various applications, including light construction, agriculture, and the marine industry. You can use them in guard rails, swing sets, and other everyday needs.
Working load limit: 2,600 - 13,000 lbs
Grade 43 chains are used in more demanding applications. These include towing, construction, and trucking. They’re often used interchangeably with grade 30 chains unless an application exceeds the grade 30 chains’ working load limit.
Working load limit: 3,150 - 15,800 lbs
Among the carbon steel chains, grade 70 is the strongest in the market due to the heat treatment used in manufacturing it. They’re usually coated in yellow chromate, giving them the appearance of gold or brass.
Grade 70 chains are the standard for tying down heavy loads and towing, which may be why they’re also often called transport chains. Still, it’s not suitable for overhead lifting. For that, you would need a stronger material than carbon steel.
Any graded chain can be used for cargo securement as long as they follow the Federal Motor Carrier Safety Association’s regulations, so carbon steel chains are cost-effective options. However, you can’t use them in overhead lifting applications.
For overhead lifting applications, alloy steel chains are the only graded chains OSHA recommends for rigging. You can use them to construct chain sling assemblies in addition to all the various securement and towing applications that carbon steel chains are capable of. They’re much stronger and have a higher resistance to bending or breaking when overloaded or sustaining impacts.
These are the most commonly used types of alloy steel chains:
Working load limit: 3,500 - 18,100 lbs
Both grade 80 and 100 steel alloy chains are suitable for heavy-duty lifting and towing applications. Since grade 100 chains are stronger, you might be wondering why you would use grade 80 chains.
Grade 80 chains are preferable and often mandated in high-heat environments such as steel mills. They’re tempered at a higher temperature than grade 100 chains. This makes them more resistant to degradation caused by extreme heat.
Working load limit: 4,300 - 22,600 lbs
Grade 100 chains are the strongest among readily available chains. Their strength-to-weight ratio is about 25% higher than grade 80 chains’.
Most of the time, a grade 80 will suffice. However, you may need a grade 100 if the chain’s application is heavily concerned with the strength-to-weight ratio.
Compared to carbon steel chains, alloy steel chains have a higher strength-to-weight ratio. They also have a much higher maximum elongation percentage of 20% before breaking. That said, it’s advisable to replace it before it reaches that point.
Lastly, there are the stainless steel chains. While their working load limits are relatively low compared to the other graded chains, they have high resistance to degradation.
Working load limit: 660 - 11,000 lbs
Grade 50 chains are made of type 316 stainless steel. Though relatively uncommon, they’re the only stainless steel chains OSHA approves of for overhead lifting applications when properly tagged.
Grade 63 chains are used in applications involving chemical exposure, such as food processing. This is because they have high resistance to heat, rust, chemicals, and saltwater.
Southeast Rigging provides a wide variety of high-quality rigging chains and hooks. Find the right hardware for your project with the help of our expert sales representatives.
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