Charging and Measuring Blast holes

All blast holes should be cleaned immediately after the drilling to ensure they are clear and are drilled to the correct depth. This is particularly important in broken and joined ground which falls in easily. Blast holes should be plugged immediately after drilling to prevent water, rocks and drill cuttings from entering the hole. Drill cuttings and rock may need to be cleared from around the collar to prevent these from falling into the blast hole during charging

All blstholes must have their depth measured and recorded immediately before charging. Short blastholes can lead to over charging toe, and digging problems, while overcharged blast holes cause fly rock hazards, noise, and reduce the effectiveness of the explosives.

Blast holes which are too deep must to back filled to the correct depth to prevent excessive vibration and damage drilled are also caused by excessive blast hole depth on upper benches. Bore hole charging, any blocked blast holes should be cleared with a charging pole or steel bar. It may be necessary to bring a drill back to the blast to clear, or re-drill some blast holes. A torch or mirror is often useful to examine the blast hole for blockages, cavity or rough sections before charging. 

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The bottom primer should be lowered until it just rests on the bottom of the blast holes. If ANFO or Energan explosives are being used, pull the primer up at least 1m. When charging Powergel, leave the primer on the bottom of the blast hole until after pumping of the charge has commenced then lift it out of any mud on the bottom. Secure the down line at the collar of the blast hole.


The technique for positioning top primer depends on the explosive type being charged. In blast holes charged with ANFO or Energan Gold, top primers can be lowered into the blast hole before charging commences. Alternatively, the primer may be lowered to the correct location as the blast hole is being charged. Secure the down line at the collar, and ensure it cannot be pulled into the blast hole as charging continues. 

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A Crying Boy. 1955 PhotoN G Nair Kerala travel 2010Ever since my early childhood days in Vaikom Kottayam Dist. Kerala (where I grew up in a rural village) called thottakom I had been fascinated by the monsoon rainsBorn as the son of teacher at Thottakom Vaikom, Kottayam District. Kerala State Mountain ranges in Kerala consisting of the highland area of the Western Ghats

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