OHS Code Explanation Guide

Published Date: July 01, 2009
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Part 21 Rigging

Section 292 Breaking strength

Subsection 292(1)

To guard against failure of a rigging component due to shock load, overload, wear, etc., the load being lifted should not exceed the Safe Working Load (SWL). The SWL is calculated as a fraction of the weakest component’s actual breaking strength. Breaking strength is the measured load required to “break” the component. SWL is calculated by dividing that breaking strength, as identified by the manufacturer or a professional engineer, by a “factor of safety”.

Subsections 292(1)(b) and (c)

“Fatigue” is the tendency of material to break under repeated stress. “Fatigue rating” means that the rigging will provide improved fatigue resistance when rated in accordance with CEN Standard EN 1677-1: 2000, Components for slings – Part 1: Forged steel components grade 8. This standard specifies mechanical properties and test procedures for forged steel components to be “fatigue rated”.

Fatigue rated rigging components can be subjected to increased loads when compared to rigging components that have not been fatigue rated. This provision permits the use of lifting chain and other hardware at a design factor of 25 percent (4:1), provided fatigue testing has been done by the manufacturer according to CEN Standard EN1677-1: 2000 Part 1.

Section 292.1 lists minimum safety factors that apply to specific wire rope rigging components. For all other components, the safety factor is

(a) 20 percent of the component’s ultimate breaking strength if the component is not fatigue rated according to EN standard 1677-1: 2000 – a safety factor of 5:1, or
(b) 25 percent of the component’s ultimate breaking strength if the component is fatigue rated according to EN standard 1677-1: 2000 and not used to raise or lower a worker – a safety factor of 4:1.

Subsection 292(2)

The factors of safety specified in subsection (1) can be modified for a dedicated rigging assembly, the use of which is restricted to a specific lift and is designed and certified by a professional engineer as safe for that lift. Once the specific lift is completed, the dedicated rigging assembly must be re-rated according to subsection (1) if it is to be used again.