Rigging
WLL vs SWL
01 — Definition
Two terms for rated capacity that are no longer interchangeable in modern practice. The WLL (Working Load Limit) is the manufacturer's rating, fixed by design and safety factor. The SWL (Safe Working Load) was the older term, one a competent person could reduce for specific conditions — wear, angle, environment. Modern standards favour the WLL, and where an SWL still appears it may already have been derated below the WLL.
02 — In the field
Treat the WLL as the ceiling and any stated SWL as a possibly lower, situation-specific limit. Never load to the WLL assuming the SWL is the same: the SWL may have been derated for a reason you cannot see on the sling.