OHS Code Explanation Guide

Published Date: July 01, 2009
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Part 6 Cranes, Hoists and Lifting Devices

Section 101 Limit devices

Subsection 101(1)

Limit devices are not to be used as operating “stops”. An operator must not operate a crane in which jumpers or by-passes have been installed in any limiting device, except under the supervision of a competent person and with the express authorization of the crane supplier.

Subsection 101(1)(a)

The overload device should be a hoist cable overload “cutout” that is set to cut out at no more than 5 percent suspended load. See Figure 6.37.

Figure 6.37 Examples of hoist cable overload cutouts

Subsection 101(1)(b)

“Movement“ means a tendency to produce motion about a point of axis. The movement overload limit device senses the tension in the jib pendants, support cables, etc. This tension increases as the load moves out on a jib or as heavier loads are lifted. It must be set to “cutout” at no more than 5 percent overload. This device must also “cutout” the trolley as it is possible to overload the crane within the rated capacity at close radius simply by moving the trolley out along the boom. See Figures 6.38 and 6.39.

Figure 6.38 Examples of location of moment overload cutout switch and switch performance

Figure 6.39 Example of travel limit switch performance

Subsection 101(1)(c)

A height limit switch causes the hoist drum to stop whenever the load hook reaches a predetermined maximum height position. See Figure 6.40.

Figure 6.40 Example of height limit switch

Subsection 101(1)(d)

Trolley travel limit devices automatically prevent the trolley from running into either end of the track (see Figure 6.41).

Figure 6.41 Trolley travel limits

Subsection 101(2)

“Sealing” limit switches means to ensure that only authorized workers can adjust them. The employer can choose the most effective method as long as it does not conflict with the manufacturer’s specifications.