A Safe Working Load (SWL) as defined by the United Kingdom’s Health and Safety Executive (HSE) as “a value or set of values based on the strength and/or stability of the equipment when lifting.” (HSE – Lifting Operations and Lifting Equipment Regulations 1998)
It also states a piece of equipment can have more than one SWL depending on the lift configuration used. A SWL is expressed as the maximum load a piece of equipment can safely lift in a predefined configuration. A SWL is calculated using an equipment’s Minimum Breaking Load (MBL) divided by an appropriate safety factor (FoS) for that piece of equipment. The Factor of Safety (FoS) used depends its construction, risk to life and expected working conditions (wear, corrosion, dynamic loads, inspection periods).
Unless otherwise stated, a SWL should be considered as the maximum safe load that can be lifted under the optimum configuration for that piece of equipment. e.g. straight line lift with a minimal lift radius, unextended telescopic boom, no fly jib, counter weights fitted, out riggers fully extended etc. (these are just some examples). Any suboptimal configuration for any lift equipment will require its SWL to be verified for that lift configuration.
The weakest SWL for any component (or combined components) within a lift configuration at any point along a loads predicted path determines the overall lift SWL. Whether it is the SWL for a crane at its maximum lift radius, or the center anchor point for a side loaded lift, the lowest SWL becomes the SWL for the complete lift.
The use of SWL by notable standards bodies around the world has been deprecated since the mid 1990s in favour of Rated Capacity for lifting equipement (eg. mobile cranes) and Working Load Limit (WLL) for lift accessories (eg. hooks, slings, beams). For more information read our article on “What is Rated Capacity and Working Load Limit”