OHS Code Explanation Guide

Published Date: July 01, 2009
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Part 36 Mining

Section 673 Misfire detonation

Subsection 673(1)

If a misfire has been identified and an effort will be made to detonate it (as compared to washing it out with water), the attempt to detonate the misfire must be done as a single hole blast. No other loaded holes or other misholes should be blasted at the same time.

The object of handling the misfire as a single hole blast is to minimize the potential for further blasting or possible dispersal of undetonated explosive products. An effort must be made to ensure the identified misfire has in fact detonated. This will reduce the hazard associated with inadvertent contact with undetonated explosive products.

Where more than one misfire is identified in the same area or blast pattern, each misfire must be handled independently.

Subsection 673(2)

If the detonation attempt is unsuccessful and the misfire clearly cannot be deactivated using a jet of water, this subsection recognizes another technique. This technique involves the drilling, charging and detonation of a parallel drill hole. Due to the extreme hazard associated with this operation, the minimum precautions that must be taken are specified. In particular, care must be taken to ensure that the drill bit does not encounter undetonated explosives in the hole. If evidence of undetonated explosives becomes apparent, all drilling activity should immediately stop and the operation should be reassessed.

Subsection 673(3)

Due to the sensitive nature of electric detonators in general, any faulty electric detonator must be handled with great care. To minimize the potential for detonation by sources of extraneous electricity, the leg wires of the faulty detonator must immediately be short-circuited. The detonator should then be handled and destroyed according to the manufacturer’s specifications.