OHS Code Explanation Guide

Published Date: July 01, 2009
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Part 23 Scaffolds and Temporary Work Platforms

Section 351 Boatswain’s chairs

Subsections 351(1) and 351(2)

A boatswain’s chair raised and lowered by manually powered hoisting equipment, or used with a “descent only” rigging arrangement, should be designed to support a minimum load of 113.7 kilograms (250 pounds). Generally, the chair will have a minimum 19 millimetre (¾ inch) thick plywood seat, attached at four corners by minimum 13 millimetre (½ inch) diameter nylon rope to a master link, or be constructed to provide a equivalent strength, and have a lap belt to secure the chair to the worker. Various designs of boatswain’s chairs are shown in Figure 23.36.

Figure 23.36 Various designs of boatswain’s chairs

A powered (motorized) boatswain’s chair is a powered platform and must meet the requirements of CSA Standard CAN3-Z271-M98 (R2004), Safety Code for Suspended Powered Platforms.

Subsection 351(3)

While the anchor to which the rope is attached must have a strength of 22 kilonewtons (5000 pounds-force), the rope must have a strength of 27 kilonewtons (6000 pounds-force). The “breaking strength” of rope means the manufacturer’s specified minimum (or nominal) strength of new rope under a straight pull test condition. The 5 kilonewton difference between rope strength and anchor strength is to allow for losses in rope strength due to factors such as the rope termination (such as knots or splices), the rope running over pulleys or other small radius surfaces, wear within generally accepted limits, and deterioration in the rope from regular use up to the time when rejection criteria require the rope to be removed from service.

Subsection 351(4)

No explanation required.