MISFIRES IN OPEN PIT MINING

The unlucky instances in open pit blasting are misfires. The instances of misfire can be all but eliminated if well-trained, careful blasting crews and blasters are employed. When a blaster checks his blast area and states that a misfire does occur, the one who conduct the blasting activity (or the supervisor) has to still ask all blockers staying on position to block human and light vehicles.

In most instances, misfires are not a result of poor product. Instead, they occur because of:

1) the negligent use,

2) cut-off of the surface delay,

3) defective product, or

4) ignorance in the proper use of the product.

 

When a misfire does occur, the degree of hazard depends on the the type of explosives used in the blasthole. In the general cases, if the blastholes are relatively intact, the explosive should be shot in place. Shooting in place is the least hazardous method of handling the misfire.

However if the blasthole is broken away and in-hole delay can not be connected again with the initiator, you can make a new borehole with radial distance 3 m of the misfired blasthole. Ather that, fill it out with explosives and detonate it.