Preparation of charge
- The charge for blasting a hole may consist of one or more explosive cartridges.
- One of the cartridges should have a detonator inshearted into it,such cartridge is known as priming cartridge.
- In case of priming,open the cartridge at one end,make hole with s pricker of brass or wood, andinshearted the detonator until it completely entered in the explosives.
- Tie or hitch the lead wire of detonator around the cartridge to prevent the detonator being withdrawal accidentally during charging.
- After placing the explosive cartridge in the drill hole the primer cartridge pushed last of all,so that the business end of the detonator face towards the main body of the drill hole.This position of the primer catridge is known as direct initiation.
- When the primer cartridge is placed fast of all in side the drill hole and the business end of the detonator face toward front of the hole and this position is called inverse initiation.
- After explosive catridges are place in the hole,the hole is stemmed with stemming material keeping the end of the lead wire of detonator out of the hole.
- The stemming material consist of sand and clay in the ratio of 3:1.
- The stemming material is of 150mm to200mm long and 20 to 30mm diameter.
- The first two or thre catridge should be tamped lightly by a stemming rod other stemming material should be tamped hard.
Complete procedure of shot firing by short firer
- The whole procedure which the shotfirer has to follow is mentioned below.
- Test the hole for break if a crack is found the hole shalln't be changed.
- Test for gas(CH4) From the hole with in 8m of the hole.
- Mark direction of drill hole on the roof and side where practicable.
- Charge the hole with explosive catridges and primer cartridge.
- Stem the hole upto its mouth by the use of stemming material.
- Spry stone dust or water in 18m of the area.
- Warn the worker to clearup and place themselves suitable at lest 27m away in any approach road.
- Lay out the shotfirer cable.
- Test again for ges with in 18m
- Connect the one end of the shotfiring cable to the lead wire of the detonator and another end to the exploder.
- Take shelter.
- Shout a warning ⚠️ again to ansure that workers have taken shelter.
- Fired the hole by a sharp twist of the exploder key.
- Allow the fume and gas to clear .
- Returned to the face to examing the roof and support etc.
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