What Is Working Load Limit - WLL?
An example of working load limit and the requirements of your tie-down system.
Working Load Limit (WLL) is the maximum load a component or assembly should be subjected to during routine use. These values apply to new products in normal working conditions and are marked by the manufacturer on the synthetic web tie down assembly or other cargo securement system.
U.S. Department of Transportation regulations subchapter B-Motor Carrier Safety Regulations, 49 CFR, Part 393, Paragraph 393.102(b) requires that: "The aggregate working load limit of the tie down assemblies used to secure an article against movement in any direction must be at least 1/2 times the weight of that article."
Example of Working Load Limit and Determining Tie Downs Needed
- Weight of article being secured is 24,000 LB
- Working Load Limit of the synthetic web tie down is 3,333 LB
- Required aggregate Working Load Limit is: 1/2 x 24,000 LB = 12,000 LB
- Minimum number of tie downs: 12,000 LB / 3,333 LB = 4 tie downs
In the above example only the weight of the object is in consideration. Other factors also determine the number and location of tie downs.
Weakest Point of the System Effects Working Load Limit
Caution: the component with the lowest working load limit capacity of the entire system determines the strength. All components should be regularly inspected for wear and replaced as necessary.