Failure Force of Webbing Sling & Roundsling

The failure force, also known as the ultimate tensile strength or breaking strength, refers to the maximum amount of force or load that a material or object can withstand before it fails or breaks. It is a critical measure of the material's or structure's strength and durability.

In the context of lifting slings like webbing slings and roundslings, the failure force is the maximum load that the sling can support before it breaks. This load is determined by the materials used in the sling's construction, its design, manufacturing quality, and other factors as mentioned in the previous response.

For example, if a webbing sling has a specified failure force of 10,000 pounds, it means that the sling can handle loads up to 10,000 pounds before it reaches a point of failure, assuming all conditions are ideal and within the manufacturer's guidelines.

According to European Standard EN 1492-2:2000, the minimum failure force for the roundsling core in straight pull shall be such that it will sustain a force equivalent to 7 times the WLL when the sling is tested in accordance with EN 1492-2,  but during the test the cover shall not rapture at a force equipvalent to less than 2 times the WLL. The roundsling shall not be pre-loaded prior to testing, unless all roundslings of the same type are subjected to identical pre-loading.

It's important to emphasize that when using lifting equipment like slings, working loads should always be well below the specified failure force to ensure safety and prevent accidents. 
Manufacturers provide working load limits and safety factors to account for uncertainties and potential variations in real-world conditions. Always follow the manufacturer's recommendations and industry standards when working with lifting equipment.