What does SWL mean?
SWL stands for Safe Working Load. It is the maximum mass that lifting equipment or lifting tackle is rated to lift, lower or suspend under normal working conditions. The figure is set by the manufacturer and is derived from the equipment’s breaking strength divided by a safety factor.
Internationally, SWL has largely been phased out because the word “safe” implied that any load below the figure was safe in every situation – which isn’t true. In South Africa, however, SWL is still widely used on site and in the Driven Machinery Regulations, so you will see both terms.
What does WLL mean?
WLL stands for Working Load Limit. It is the maximum load the manufacturer permits the equipment to carry in a specified configuration – for example, a sling used in a straight vertical lift. WLL is the term now used on most new slings, shackles, hooks and chain components.
For cranes and hoists, where capacity changes with boom length, radius and configuration, you will usually see Rated Capacity or Manufacturer’s Rated Capacity (MRC) instead, read off the crane’s load chart.
SWL vs WLL: is there a difference?
In day-to-day practice, SWL and WLL refer to the same number for a given item used as the manufacturer intended. The differences are in wording and emphasis:
| Rating | What it means | Where you’ll see it |
| MBL – Minimum Breaking Load | The load at which a new item is expected to fail in testing. Never a working figure | Manufacturer certificates, wire rope and chain specifications |
| WLL – Working Load Limit | Maximum load allowed in a specified configuration (MBL ÷ safety factor) | Tags on slings, shackles, hooks, chain; modern certificates |
| SWL – Safe Working Load | Older term for the same maximum working load | SA regulations (DMR 18), older equipment, test certificates |
| Rated Capacity / MRC | Maximum gross load for a crane or hoist in a particular configuration | Crane load charts, hoist data plates |
The key point: WLL may need to be reduced further on site depending on how the equipment is used — the sling angle, the type of hitch, sharp edges, temperature and shock loading all lower what the gear can safely carry. That reduced figure is sometimes still called the SWL “for that lift”.
How is SWL or WLL calculated?
The formula is simple:
WLL (or SWL) = Minimum Breaking Load ÷ Safety Factor
Example: a wire rope sling has an MBL of 25 tonnes. With a 5:1 safety factor, its WLL is 25 ÷ 5 = 5 tonnes.
Safety factors differ by material and by the standard the item is manufactured to. As a general guide, typical factors are:
- Alloy chain slings (Grade 80/100): around 4:1
- Wire rope slings: around 5:1
- Shackles: typically 5:1 or 6:1, depending on the manufacturer
- Polyester webbing slings and round slings: around 7:1.
Always use the figure on the equipment’s tag and certificate rather than working it out yourself – the manufacturer has already applied the correct factor for that product.
What does “SWL 1000 kg” mean?
A marking of SWL 1000 kg (or WLL 1 t) means the item may lift a maximum of 1,000 kg in its rated configuration. It does not mean it fails at 1,001 kg – it means anything above 1,000 kg eats into the safety margin that protects against wear, dynamic loading and hidden damage. That margin is not spare capacity, and using it is a breach of the equipment’s rating.
Why sling angles change the real working load
This is where many lifts go wrong. When you lift with a multi-leg sling, the legs are pulled outward as well as upward. The wider the angle between the legs, the more tension each leg carries — even though the load hasn’t changed.
Here is the tension in each leg of a two-leg sling lifting a 10-tonne load:
| Angle between the two legs | Angle of each leg from vertical | Tension in each leg |
| 0° (legs vertical) | 0° | 5.0 t |
| 60° | 30° | 5.8 t |
| 90° | 45° | 7.1 t |
| 120° | 60° | 10.0 t |
At a 120° included angle, each leg carries the full weight of the load. That is why sling manufacturers publish reduced ratings for different angles, and why most rigging practice limits the included angle to 90° (45° from vertical) wherever possible, and never above 120°. Choke hitches and lifting over sharp edges reduce capacity further. Planning these angles is a core part of any rigging plan.
What South African law requires: DMR 18
In South Africa, lifting machines and lifting tackle are governed by Regulation 18 of the Driven Machinery Regulations, 2015, under the Occupational Health and Safety Act. In summary:
- Marking: lifting machines must be clearly marked with the maximum mass load they are designed to carry, and lifting tackle must be identifiable with its rating.
- Lifting tackle inspections: slings, shackles and similar tackle must be examined by a competent person at intervals not exceeding three months, with results recorded in a register.
- Lifting machine examinations: cranes and other lifting machines require a thorough examination and performance test by a registered Lifting Machinery Inspector (LMI) or Lifting Machinery Entity (LME) at intervals not exceeding 12 months.
- Load testing: where no manufacturing standard sets the test, installations are typically load tested at 110% of the SWL.
- Records: a register of tests, examinations, modifications and repairs must be kept on the premises.
Equipment that is unmarked, untagged, out of inspection date or visibly damaged must be taken out of service – regardless of what it is rated for. Our lifting equipment inspection checklist covers what to look for, and our guide to rigging team certifications explains who is qualified to sign off.
Five rules for working with load ratings on site
- Know the load weight – confirm it from drawings, data plates or a load cell, never by guesswork.
- Use the lowest-rated component – a lift is only as strong as its weakest shackle, sling or hook.
- Apply angle and hitch reductions before you choose the sling, not after it’s rigged.
- Check tags and inspection dates on every item before each lift.
- Allow for dynamic loads – snatching, swinging and sudden stops can momentarily exceed the static weight.
For more on choosing the right gear, see how to choose the right rigging equipment and our list of common rigging mistakes.
Need a lift planned and rigged correctly?
Reef Rigging plans and executes heavy lifts, machinery moves and installations across South Africa, with certified riggers and inspected, tagged equipment on every job. If you’re unsure whether your lift is within the ratings of your gear, contact our team or call +27 82 659 3315 to talk it through.
Frequently asked questions
What does SWL stand for in lifting?
SWL stands for Safe Working Load – the maximum load a piece of lifting equipment is rated to carry under normal working conditions, calculated as the minimum breaking load divided by a safety factor.
What is WLL?
WLL is the Working Load Limit: the maximum load a manufacturer allows on lifting equipment in a specified configuration. It is the modern replacement for the term SWL.
Are SWL and WLL the same?
For the same item used as the manufacturer intended, yes – they describe the same maximum load. WLL is the current international term; SWL is still common in South African regulations and on older equipment.
How is SWL calculated?
SWL or WLL equals the Minimum Breaking Load divided by the safety factor. For example, a sling with a 25 tonne breaking load and a 5:1 safety factor has a working load of 5 tonnes.
How often must lifting tackle be inspected in South Africa?
Under DMR 18, lifting tackle must be examined by a competent person at least every three months, and lifting machines need a thorough examination and performance test at least every 12 months.
Can you exceed the SWL if the load is only slightly heavier?
No. The margin between the SWL and the breaking load exists to cover wear, shock loading and hidden damage. Exceeding the rating – even slightly – is unsafe and non-compliant.