What Are the Different Grades of Chain?

Thursday, 29 July 2021

What is a lifting chain? How can I identify a load rated chain that is suitable for lifting? What do the letters and numbers mean? Why should I choose one grade of chain over another?

Understanding what exactly are the different grades of chain is essential knowledge if you are looking for lifting, or looking at using lifting chains for other purposes.

 

What is, and what is not a lifting chain?

Lifting chains can fall into several categories, but they all have some essential things in common:

  • They have a known strength performance.
  • They reliably achieve their strength.
  • A load rating expressed in terms of a Working Load Limit (WLL) can be determined.
  • They have traceability – i.e. markings which match a physical piece of chain to its manufacturing and test documentation.
  • Their ultimate performance characteristics make them safe for a lifting application.

 

What does a lifting chain look like? 

This is a question which should be easy, but there are a couple of exceptions which we should all be aware of.

Why do we say ‘should be easy’? Well, that’s interesting because there’s one good reason why this should be the case, and three main reasons why it isn’t.

Anyone who walks out into an industrial workplace and has seen ordinary lifting chains has probably noticed something – and that is how they pretty much all look the same.

Why is that?

Well, when we talk about lifting chains, we are usually describing two main things:

  • Medium tolerance, short link chains for slings, or
  • Fine tolerance, short link chains for hoists.

The key thing here is the ‘short link’.

All of these chains have a nominal pitch length (inside length) that is about 3 times the nominal diameter of the chain and this is what gives them their distinct look.

Normal lifting chains have distinctive proportions.

 

What makes this only partially helpful are the exceptions, and the major one is lashing chain for transport. This chain is ‘grade 70’ and in Australia this usually (but not always) has a gold passivated surface finish.

Grade 70 transport lashing chain (Left), A variety of lifting sling chain grades (Right).

This chain is a bit like the lifting chain that never made it to the big time. It looks pretty similar, but doesn’t have the same manufacturing controls or strength as most lifting chains.

It is very important that grade 70 transport chain is not substituted into grade 80 and higher chain slings, or reeved into a hoist.

We did say there were other exceptions.

The first of these is a simple one to beware of, and that is a simply untraceable chain.

Unfortunately, there is no restriction on making chains that have the same shape and colour as ordinary lifting chains. This may or may not be a lifting chain, but it cannot be identified and is therefore unsafe.

The second exception is all of the lifting chains that fall into some kind of special circumstance category, these might be chains which are hand forged and engineered from specialised materials, or they might be the chains which do a lifting job sometimes, but by nature of their extreme size are the only option. Large stud link chains used to lift ships anchors might be an example of this, but there are numerous others. These are not lifting chains found in everyday workplaces.

 

The great divide - sling chain and host chain. 

Amongst lifting chains, the most major distinction is between the chain we use for slings, and the chain we use for hoists.

The chain for slings must be: tough and ductile.

This makes it safe for such things as being wrapped around loads, run across hooks in a choke hitch, and all of the dynamic rough and tumble events in a properly used chain sling’s existence.

Chain slings for hoists must be: precise, and hard wearing.

The hoist chain is only ever allowed to be pulled in a straight line, over or between the support given by the load chain wheels built into the hoist. To work with those load chain wheels, however, the chain must be made to an extra precise size and pitch, otherwise, it may bind, skip, jump and even throw sparks during operation. For some hoists, surface hardening is also applied to keep it precise – but this is only permitted in certain hoists because it reduces the chain’s toughness.

Hoist chain is lifting chain, but not for use in slings.

 

How can we tell which chain is which? 

This is another one of those – ‘should have been simple’ things.

Within the ISO standard, the hoist chain is marked with letters denoting the grade and sling chain numbers.

Unfortunately, though, there is also historical use of letters and in Australia particularly, grade T as a designation for sling chain is very common. There are also brand name designations that make things less simple.

To this day, our Australian Standards allow for letters on sling chains. The latest editions adding V200 and V400 as versions of grade 100 using both letters and numbers.

Within the numbering system itself there is confusion, so grade 10 usually means grade 100 and is a higher grade than grade 30.

The truth is, that identifying the grade is the task of a competent sling and hoist inspector. The end user is directed only to the sling tag or hoist data plate.

With that said, however, we should point out that VH, DAT and DT chains could be particularly bad if found in a sling, and that in general, we should expect to see numbers amongst the grade markings on the sling chain.

 

Where do the numbers come from?  

This is simple to explain in terms of the calculation.

What we imagine is that we’ve cut the chain right across its middle and measured the cross sectional area. This is two circles and the area are easily calculated (in square millimetres). Then we apply this to the maximum force we can apply to the chain at its breaking load (in Newtons). The result if we divide the two is Newtons per square millimetre, or its equivalent value “Megapascals” (MPa).

This number might be 800MPa for example, and depending on what’s convenient to the chain maker

Some zeros might get knocked off that figure to give us either grade 8, 80, or 800 chain – which all mean the same thing.

Actually – the calculation works the other way of course. When a standard is set for a chain, we start with the nominal tensile and then work back to discover the minimum breaking load that will be set for each size of the chain.

Notice that we say ‘nominal tensile’. This is because the calculation is done on the least stressed part of the chain. In order to be strong enough, we have to use steels that are significantly stronger (that means a much higher tensile) than the nominal tensile that gives us the grade number.

By the way, the letter system of grades is remarkably similar – having its origins in the tensile strength delivery ranges from steel standards dating back to the second world war.

 

Sling chain grade numbers 

There are actually lots of legitimate sling chain grades, each with their own pros and cons.

These are:

Grade L, 3, 30 or 300

Grade M, 4, 40 or 400

Grade P, 5, 50 or 500

Grade S, 6, 60 or 600

Grade T, 8, 80 or 800

Grade V, 10, 100 or 1000

Grade 12, 120

And let’s not forget the other lifting chain grades either: which include such things as the stainless grades 4, 4+, 5, 6 & 6+.

Of these, the Australian Standards currently recognise grades 30, 50, 80, 100 and (for stainless) grade 5.

 

So-called 'Commercial' chain.  

If you go searching for each of the standard lifting chain grades, you may come across a couple of ‘phoney’ versions of the lower tensile chain grades. Low tensile lifting chain can be very useful with its extra thickness, environmental resistance and ability to be safely galvanised – but so-called commercial grades that get sold using names like ‘grade 30’ and ‘proof coil’ are not lifting chains. Neither are true AS2321-2014 grade 30 nor suitable for use in a proof tested lifting sling.

Commercial chain comes in many different sizes and finishes but must not be used for lifting

Commercial chain grades are also unsuitable for road transport lashing.

This is usually not a problem when you physically look at the chain. Commercial grades of chain and other non-lifting grades like trailer chains are almost never ‘short link’ and don’t bear the appropriate markings and traceability required in order to assign them a WLL.

 

Think Nobles for lifting chains.  

Nobles is a leading manufacturer of chain slings in Australia. Nobles chains are manufactured to comply with Australian Standard 3775 and all chains manufactured by Nobles are fully proof tested to twice the WLL.

 

NOBLE10 grade 100 lifting chain 

NOBLE10™ Grade 100 chain is stronger and more durable making it ideally suited to the construction, mining, manufacturing and heavy engineering industries. It is offered in pre-assembled or made-to-order slings for Nobles’ customers nationally.  NOBLE10™ chain is a reliable and cost-efficient product that is available in true Grade 100 alloy chains ranging up to 32mm in diameter, together with a choice of fittings.  Noble10TM chain comes painted in blue powder coated finish and is marked with full product traceability code.

 

We can help you choose the right chain 

Nobles is the leading national specialist supplier of lifting and rigging equipment and services to Australia’s mining, resources, industrial, construction, infrastructure, defence and other industries.  Founded in 1911, Nobles have been supplying quality products and services to Australian markets for 110 years. Today Nobles offer its customers complete solutions for: lifting and rigging equipment; technical and crane maintenance services; and engineering design. Nobles has 14 locations around Australia.

If you are interested in learning more or speaking with a Nobles Service Support Team about your chain options, email us at sales@nobles.com.au or phone 1300 711 559!

 

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