SWL vs MBL
Safe Working Load is the in-service rating; Minimum Breaking Load is the failure load. SWL = MBL / safety factor (typically 5).
In practice
Lifting-equipment register lists SWL of every appliance. The SWL is what crew apply in service; MBL is the test value, never relied upon operationally.
Regulatory detail & full definition
Safe Working Load is the maximum in-service load assigned to a piece of lifting or mooring equipment; Minimum Breaking Load is the load at which failure occurs in test conditions. SWL = MBL divided by a safety factor that depends on equipment type and applicable code — for general lifting under ILO Convention 152 the factor is 5; for mooring lines under OCIMF MEG4 the line design break force concept replaces the simple ratio with a more nuanced approach. Markings on lifting equipment must show the SWL clearly and unambiguously.
Authoritative source: OCIMF MEG4 ↗
Related
Source: ILO Convention 152; OCIMF MEG4
High confidence
Editorial confidence: how we grade.