OHS Code Explanation Guide

Published Date: July 01, 2009
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Part 36 Mining

Section 679 Secondary blasting

Subsection 679(1)

These are standard procedures commonly used in coal mines. They are legislated to stress the importance and necessity of strict compliance.

For example, the use of larger charges will cause a larger explosion and increase safety hazards. The limit of 0.5 kilograms of explosives is designed to keep the blast to an acceptable size and limit safety hazards for workers.

To minimize the potential for causing a catastrophic methane/coal dust explosion, the area surrounding the “top” charge must be cleared of coal dust and must be adequately rock dusted to within a 10 metre radius of the planned charge.

Subsection 679(2)

This subsection restricts secondary blasting if the methane content in the surrounding area is more than 0.3 percent (6 percent of methane’s lower explosive limit).

Subsection 679(3)

Since the hazards associated with secondary blasting e.g. flyrock, vibration, can be greater than in normal mine blasting, the place of refuge for the blaster must be at least 150 metres from the blast site. This compares to the 75 metres required for normal mine blasting.