The maximum load that lifting gear, mooring lines, or deck equipment is certified to bear without risk of failure in normal use.
In practice
SOLAS II-1 and ILO Convention 152 (Occupational Safety and Health in Docks) impose requirements on the testing and certification of lifting appliances. Classification society rules and flag state regulations specify inspection and proof-load testing intervals — typically every five years for cargo gear. Under MLC 2006, shipowners must ensure that equipment is maintained in a safe condition and that seafarers are not required to handle loads beyond certified limits. The bosun and cargo officers are responsible for checking SWL markings before operations and for removing from service any equipment whose marking is missing, illegible, or whose certification has expired.
Regulatory detail & full definition
Safe Working Load (SWL) is the maximum load, expressed in tonnes or kilonewtons, that a piece of lifting equipment, mooring line, wire rope, shackle, block, or other deck fitting is certified to bear under normal working conditions without risk of failure. The SWL is derived from the minimum breaking load (MBL) of the component divided by a specified factor of safety, which varies depending on the application — lifting gear generally requires a higher factor than mooring lines. The SWL must be marked or tagged on the equipment and must not be exceeded.
SOLAS II-1 and ILO Convention 152 (Occupational Safety and Health in Docks) impose requirements on the testing and certification of lifting appliances. Classification society rules and flag state regulations specify inspection and proof-load testing intervals — typically every five years for cargo gear. Under MLC 2006, shipowners must ensure that equipment is maintained in a safe condition and that seafarers are not required to handle loads beyond certified limits. The bosun and cargo officers are responsible for checking SWL markings before operations and for removing from service any equipment whose marking is missing, illegible, or whose certification has expired.