Complete Guide to Lifting Slings: Types, Capacities, and Safety

Lifting slings are among the most versatile and widely used tools in material handling. Whether you're lifting a delicate machine part, a concrete pipe, or a steel beam, the right sling can make the job safer, faster, and more efficient.

In this comprehensive guide, we'll cover everything you need to know about lifting slings: types, capacity ratings, color coding, inspection, and safe usage practices.

What is a Lifting Sling?

A lifting sling is a flexible device used to attach a load to a lifting hook or crane. Unlike chains or wire ropes, slings are soft and conform to the shape of the load, distributing pressure evenly and avoiding damage to the lifted object.

Types of Lifting Slings

1. Round Slings

Round slings are endless-loop slings made from high-tenacity polyester fibers encased in a protective tubular cover. They are the most popular type of sling for general lifting because of their flexibility, strength, and load-protective properties.

• Infinite adjustment: Can be wrapped around any shape
• Flexible: Conforms to irregularly shaped loads
• Non-marring: Will not scratch or damage painted or polished surfaces
• Lightweight: Easy to carry and position

2. Webbing Slings

Webbing slings are flat-woven polyester straps with sewn eyes at each end. They offer better stability for certain loads and are commonly used in construction and heavy rigging.

• Stable load control: Wide flat surface prevents load rotation
• Easy inspection: Flat surface makes wear visible
• Standard lengths: Available in fixed lengths with eye ends

International Colour Coding System

Webbing slings (EN 1492-1) and round slings (EN 1492-2) share a standard colour code tied to the working load limit. It exists so an operator can identify a sling’s capacity at a glance, without reading a label in poor light.

Two cautions about the colour code. First, the colour states the limit for a single vertical lift — it says nothing about what the sling can carry in a choke hitch or at an angle, which is covered below. Second, there is no standard colour above 10,000 kg; larger slings are identified by their label alone. And a colour is not a substitute for the label: if the label is missing or illegible, the sling should be taken out of service regardless of what colour it is.

Rigging Configuration & Effective Capacity

A sling’s rated capacity only applies to one specific arrangement: a single vertical lift. Change the hitch, or use more than one leg, and the effective capacity changes. The multiplying figures are called mode factors, and they are the numbers that catch people out.

Two things follow from this table, and both matter more than they look.

• A choke hitch reduces capacity, it does not add it. The sling is bent sharply around the load and the load is carried on a fraction of the sling’s width, so a green 2-tonne sling choked becomes a 1.6-tonne sling. The same sling in a basket hitch genuinely doubles, because the load is shared across two thicknesses of sling.
• Wider leg angles reduce capacity, not increase it. This is the counter-intuitive one. Splaying two legs wide feels as though it should spread the load and make the lift easier. In fact the tension in each leg rises sharply as the angle opens, which is why the mode factor falls from 1.4 to 1.0 as the included angle passes 45°. A two-leg sling used at a wide angle can be loaded well beyond its rating while looking perfectly normal on the hook.

Use the capacity chart on your own sling’s label as the authority, not a table from an article. Mode factors vary slightly between standards and between manufacturers, and the label that came with the sling you are holding is the figure that applies to it.

The Angle Effect, in Plain Numbers

If you take one thing from this guide, take this. As the angle between sling legs widens, the tension in each leg grows — and it grows faster than most people expect.

At a 120° included angle, each leg carries the entire weight of the load rather than half of it. Keep included angles at or below 60° wherever the rigging allows, and treat anything past 90° as a configuration to be re-planned rather than merely accepted. Longer slings, or a spreader beam that takes the angle out of the equation entirely, are the usual fixes.

Reading a Sling Label

A compliant sling carries a label with more information than most operators realise. Before using an unfamiliar sling, check it for:

• Working load limit, and the mode factors for the configurations it is approved for
• The standard it is made to — EN 1492-1 for webbing, EN 1492-2 for round slings, or ASME B30.9 in North America
• Material, usually polyester (PES), nylon (PA) or polypropylene (PP)
• Length and colour, so the sling can be identified from the ground
• Manufacturer and traceability reference, which matters if a batch is ever recalled
• Date of manufacture, since slings have a service life as well as a condition requirement

A sling with a missing or unreadable label should be withdrawn from service. Without the label there is no way to know its capacity, and an unmarked sling in a rigging store is a hazard waiting for someone to guess.

Materials and What They Tolerate

All three are damaged by the same things in practice: heat, sharp edges, and chemicals. A sling that has been glazed, melted, stiffened or faded has lost strength even if it looks structurally intact, and the melting or glazing point is exactly where it will fail. Store slings away from sunlight and from anything that off-gasses or drips.

Sharp Edges and Edge Protection

The most common way to destroy a sling is also the most avoidable. A loaded polyester sling pulled across a sharp corner will cut, and it will cut at a fraction of the load it would otherwise carry. If there is any edge in the lift that would mark your hand when you run it along, it needs protection.

• Use edge protectors, sleeves or corner guards at every contact point with a sharp or machined edge
• Never drag a sling across a floor, edge or another sling under load
• Reduce the load further for any lift on an edge that cannot be protected — do not simply accept the standard mode factor
• Inspect the contact area after every lift for cuts, abrasion and pulled yarns, not just before

Inspection & Retirement Criteria

Lifting slings must be inspected before each use. Remove from service immediately if you see:

• Cut or torn core yarns (visible through the cover)
• Frays, cuts, or worn areas on the webbing
• Heat or chemical damage (melted, glazed, or hardened areas)
• Missing or illegible capacity tag
• Knots or kinks in the sling body
• Broken or deformed fittings (eyes, rings, hooks)

Storage & Care

• Store slings in a cool, dry place away from direct sunlight
• Hang slings on racks — do not pile them on the floor
• Avoid contact with acids, alkalis, and harsh chemicals
• Clean with mild soap and water; dry before storing

Sling, Chain or Wire Rope?

Soft slings are not always the right answer. The choice between a sling, a chain sling and a wire rope sling is decided by the load’s surface, the environment, and the temperature.

In practice most workshops need both: soft slings as the everyday option and chain slings for anything hot, abrasive or rough-edged. The mistake to avoid is using a soft sling on a hot or sharp load because it happens to be the one hanging on the hook.

Common Questions

How often should slings be inspected?

Two levels. The operator inspects before every use — a visual check of the whole sling and the label, which takes seconds. On top of that, a documented periodic inspection by a competent person is normal practice, with the interval set by how hard the sling works: a sling used daily on abrasive loads needs far more frequent formal inspection than one used occasionally in a clean workshop.

Do slings have a shelf life?

There is no fixed expiry date; condition decides. A sling stored correctly and used lightly can give many years of service, while one used on sharp edges in sunlight may be finished in months. The label’s date of manufacture is there so an inspection regime can take age into account, not as an automatic discard date.

Can I shorten a sling by tying a knot in it?

Never. A knot concentrates stress, reduces capacity severely, and can slip or come undone under load. If a sling is too long, use a shorter one, or take a wrap around the load, or use a suitable shortening clutch designed for the purpose.

Can I use two slings of different capacities together?

It is not good practice. The assembly is limited by the weaker sling, and load sharing between legs is rarely as even as it looks — one leg almost always takes more. Use matched slings from the same batch and the same material where you can.

Are round slings better than webbing slings?

They suit different jobs rather than one being better. Round slings conform to awkward shapes and resist abrasion well, since the load-bearing yarns are protected inside the cover. Webbing slings are flatter and more stable on regular loads, and their wear is easier to see because the load-bearing surface is exposed. Many rigging stores keep both.

What temperature can a polyester sling take?

Roughly 100°C as a working ceiling, and considerably less before it starts to suffer. A sling that has been glazed, stiffened or discoloured by heat has lost strength even if the fibres are still intact. For hot work, switch to a chain sling rather than pushing a soft sling closer to its limit.

Choosing slings for a specific lift, or need a quote on round or webbing slings in a particular capacity and length? Tell us the load and the configuration and we will confirm the capacity you need — or see the range on our lifting sling product page.

Browse our complete range of lifting slings for more details.