Charge Preparation for Blating in Mines

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In this post we will discuss about the Charge preparation for underground blasting...

For blasting, the charging of hole may consist of one or more cartridge and the separation of cartridge should be least as much possible. Among the charged explosive in a hole, it is necessary that a Detonator is inserted in one of the explosive. The cartridge having Detonator in it, called prime cartridge.
To insert Detonator, a hole is maked with a Pricker of brass or wood.

Insert the Detonator until it is completely buried in explosive after that put back the flap of cartridge and bind the cartridge around with wire to prevent the detonator to come out during charging.

Charging of Shot Holes

Proper charging of shot hole is important to get the desire results. We follows two methods to Charge the holes..

1. Direct Initiation

2. Inverse Initiation


Here we will discuss these two methods..
Direct & Inverse Initiation
Preparation of Shot Hole

Direct Initiation

This is the method of Charging of holes in which the primer cartridge is placed after the other cartridge. So that the business end of detonator is points towards the main body of charge. With this charging the detonator's wave passing towards the back of hole, this increases the chance of maximum explosion.

Advantages
• This is best to prevent fire damp explosion.
• Reduces the blow out of shot hole.
• Provides maximum free face.

Inverse Initiation

When detonator is back of the charge and business end points towards the front of hole, then this charging is called inverse Initiation.
This is not practised in coal faces. But somehow adopted to sum ping or tunnelling and also when delay detonators have to fire a round of shots.
After hole is charged with explosives. Now it's time to stem the hole with stemming material. The stemming material should be compact but plastic in nature, made up of sand and clay in ratio 3:1. The dimension of cartridge is 150 mm to 200mm length and Dia. Of 25-30mm. The first 2 to 3 cartridge stemmed light and rest are tightly with stemming rod.

*If you have any suggestions or question.... Please comment below.


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