Working load limit
Working Load Limit (WLL), also rated capacity or maximum working load is a measure of the load-bearing capacity or for the permissible working load , z. B. for ropes or load straps. WLL is a specification defined by the manufacturer.
To determine the WLL, the breaking strength is usually measured and then divided by a safety factor (SF):
The safety factor (utilization coefficient) is 4: 1, 5: 1, 7: 1 or, for mountain railways, for example 10: 1 or 12: 1. The WLL is therefore always significantly lower than the breaking load or minimum breaking load (MBL), i.e. the load at which a component (or rope ) breaks.
The WLL is indicated on a nameplate on many products or stamped on metallic objects ( snap hooks, etc.) . For slings (lifting belt, tension belt , chain , rope, snap hook, shackle, etc.), the specifications of the WLL are prescribed.
It should be noted that the specified WLL only applies under ideal conditions, for example new component, suitable operating temperature , no sharp edges, no adverse environmental influences, etc. and that the load is only vertically and statically attached to the component. For other applications, separate information is often given, e.g. for the U-shaped use of a lifting sling (see picture).
When using several interdependent parts, the lowest WLL is decisive for the total load capacity; what matters is “the weakest link in a chain”. A WLL is also specified for systems such as lifting cranes , i.e. the load that can be lifted with the system.
literature
- Linden tree: knots, stitches, bundles and slings. Hüthig Jehle Rehm, Heidelberg et al. 2011, ISBN 978-3-609-62402-0 , pp. 69-71 ( lifting accessories ) - Google Books