LIFTING ATTACHMENTS
related to safety for ‘hoist chain, Grade T (type T quenched and tempered and types DAT and DT case hardened), for use in chain hoists, whether manual or powered’. Type DAT and type DT hoist chains possess surface
hardnesses greater than core hardness. In other words, they are harder at the edge than in the middle. They are used for power driven chain hoists to offer greater resistance to wear. Type DT hoist chain differs from DAT hoist chain in having higher surface hardness and/or greater depth of hardness to optimise wear resistance still further. To answer why lifting and rigging demand different types of chain, a load chain (also known as a lifting chain) passes over sprockets – teeth – in the hoist. Therefore, it must be manufactured to precise tolerances to fit the teeth exactly, and it must not stretch or deform when it is under load. If it does, it will jam in the teeth, which could be disastrous. Also, the full weight of the load is being transmitted from the teeth to the surface of the chain; the two are rubbing against each other under great pressure. The chain surface will be abraded and wear away unless it is specially hardened.
Consequently, typical load chains are manufactured
to have hard-wearing surfaces, and to stretch only by about 5–7% at full working load. It is the opposite with rigging chains. They are designed to stretch and to deform. It is a safety measure. Rigging chains, and chain slings especially, are frequently used at an angle, as when lifting a beam by a chain between both ends. Sling angles should be at least 30 degrees; angles of 60 degrees are to be preferred. The reason is that small sling angles greatly increase the tension in the chain; it is, therefore, relatively easy to overload a rigging chain, especially in complex lifts where multiple rigging chains or slings are employed. If a rigging chain has been overloaded, a permanent stretch will be a visible warning of the fact and a strong indication that the chain should be discarded.
Overload is of course possible with load chains
too; but they are used vertically only, so stresses are easier to calculate and the hoist itself, if it is in any way up to date, will have overload sensors and audible warnings built in, thus providing an alternative route to safety. Rigging chains, therefore, are required to stretch a minimum of 20% (the ASTM requirement) before failure. For load chains, as we have seen, the figure is 5–7%.
Choosing the right tool Chain slings of course are not the only option for rigging below the hook. The wire rope sling is another and synthetic slings a third. All have their advantages and drawbacks; all have applications that best suit them. Chain slings are hard-wearing, long-lasting and
strong. They resist impacts, cuts and abrasions, and if they are damaged a link can often easily be replaced. UV light does not affect them, nor do most chemicals; they can be used in dirty, oily or many hazardous environments; and it is easy to adjust their length to
A two-leg chain sling from Lifting Equipment Store.
www.hoistmagazine.com | July/August 2026 | 29
fit the job in hand. They are heavy – sometimes very heavy – and this can make them awkward to transport, and hard to manipulate and fix in place. They are also the most expensive of the three options – though that is offset by their longer working life.
Chain slings are available from many manufacturers – Pewag, Columbus McKinnon, William Hackett, among others. They come ready-assembled with shackles and master links in single, double or quad-leg formats, and in different (but, as above, suitable) steels for different applications. For example, Grade 6 stainless steel chain slings are highly resistant to corrosion and are most commonly used in marine and food- processing environments. Higher grades such as Grade 8 provide superior strength and wear resistance for heavier-duty lifts.
Pewag LINX-8 Grade 8 chain slings for example
are available in chain sizes from 6mm to 32mm and fully conform to EN818-4 (the chain to EN818-2, the components to EN1677). There is a complication here. Grade 8 chain slings
are often casually referred to as Grade 80, and many in the industry consider the terms interchangeable. They are not. It is true that Grade 80 chain slings are rated with the same working load limits (WLL) as G8 slings. However, their steel may be different: Grade 80 slings may be manufactured using boron alloy steel, which is not allowed for G8, and a boron alloy chain will not perform equally under some extreme conditions such as high shock loads or severe temperatures when
A Green Pin shortening clutch.
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