21/10/2025
🕵🏻♂️⁉️How Did They Calculated the Safe Working Load or SWL of a Lifting/ Rigging Equipment and What is Safety Factor
🏋️♂️SWL- It is simply the MAXIMUM weight you are allowed to lift SAFELY with that equipment.
Two words:
👉 Maximum, but
👉 Safe
Example: A sling might be able to break at 100 tones, but we never lift anywhere close to that!
A safety factor is applied (say 5), FoS values (4, 5, 7, etc.) are defined in lifting standards
👷 What is a Safety Factor or Factor of Safety (FoS)
✳️ these are whole numbers or factors applied to the breaking strenght of a material, as defined in lifting appliances standards either by US or European Standard
Calculate/ Formula:💁🏻♂️
SWL = Sling breaking strength / FoS
SWL = 100tons / 5 = 20 tons
✳️ Purpose of Safety Factor or Factor of Safety (FOS)
👍 it creates a margin for uncertainties in case of unexpected excess forces or malfunction. We calculated this characteristic by the structural strength divided by the minimum structural strength required.
🧐💭Remember this:
🔖The Greater the safety factor, the lower the likelihood of structural damage is and the more stress the structure can take.
Therefore, the safety factor serves to determine the maximum load that lifting equipment can withstand safety when in use and ensures safe operations.
✳️Understand The Factor of Safety (FoS) represented as a RATIO
example,
if your equipment needs to lift 2,000 kg, and its safety factor is 4:1, the equipment will be designed up to 8,000 kg.
This equipment has a Breaking Strenght of 8000kg, divide by Factor of Safety as 4, therefore the SWL = 2000kg
😊Very safe to use right?, even if you lift the maximum SWL weight, but still it will not break because its BS is 4x the SWL
🚢⛴️🛳️
The factor of safety depends on the materials and the use of equipment.
When designing any lifting solution, equipment makers need to calculate the forces to be applied to the equipment to establish safety limits.
📚📖🏋️The legal requirements for safety factors for lifting equipment
🇺🇸In the US and the 🇪🇺EU, it has to be the following FoS is required:
☑️Rigging Equipment:
between 4:1 and 7:1
☑️Hoisting Device:
between 2:1 and 3:1
🧔🏻Conclusion:
Next time you see markings of Safety Factor in your Lifting Equipment, auch as Chain blocks, do not be afraid to see the SWL, check first for the factor, by then you will know the Breaking Strenght of that device is far more than the SWL, but of course it is safer not to exceed the SWL.
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