OHS Code Explanation Guide

Published Date: July 01, 2009
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Part 21 Rigging

Section 292.1 Safety factors

Non-rotating line (often used as a single part hoisting line)Subsection 291.1(1)

The total stress in a wire rope, in service, is composed of several separate elements. These are reduced to a single tensile load value (working load). When this value exceeds the breaking strength of the wire rope, a failure occurs.

The factor to provide a margin of safety between the applied tensile forces and the breaking strength of the rope is defined as the safety factor.
Except as provided in section 292, the safety factor for wire rope used in various applications is as follows:

Running line (also known as hoisting line)
(Running line on overhead cranes is typically 5:1)

3.5 to 1

Non-rotating line (often used as a single part hoisting line)

5 to 1

Tugger lines (lines on a small drum winch), for pulling only
(Tugger lines used for hoisting must be 5:1)

3 to 1

Pendant lines (attached to and support the boom head)
Guy lines (stabilizing structures, etc.)

3 to 1

Winch lines (typically mounted on a truck or crawler tractor)

2 to 1

Subsection 292.1(2)

Impacts or sudden “jolting” when towing can pull rigging components and lines into yield (stretching). Yield reduces ultimate breaking strength which may reduce the factor of safety necessary for lifting service.