Explosives and Blasting
In the US and Canada alone, blasters use more than 6 billion pounds of explosives and 75 million detonators per year. Coal mining accounts for two-thirds of consumed explosives of which more than 80% of it is ANFO.
Today, sophisticated explosive materials and new technologies are being utilized to improve the quality of life for all of us. Computers are used to: drill,log and monitor blastholes — automate blending and delivery with bulk trucks — determine bench heights and face conditions — analyze production efficiency, design blast patterns — and more.
The time line below presents the history of the explosives industry... a tradition of excellence in mining, quarrying, construction, and many other pursuits involving the peaceful use of for explosives inunderground mines.
How Explosives Work
Explosives are chemicals and, like all chemicals, should be treated safely and with respect.
Unlike other chemicals, most explosives detonate rather than burn. A detonation is a very rapid chemical reaction using oxygen that is contained in the material rather than in the air. In a detonation, the chemical reaction releases gases that rapidly expand and giveoff energy as they become hot.
Two Basic Types
Explosives are categorized into two basic types, low explosives and high explosives. Low explosives tend to deflagrate, rather than detonate, which means that they burn at a slower rate and create less pressure than high explosives. Low explosives are often used as propellants to force a bullet out of a gun or send a rocket into space.
For many years, black powder was the most common low explosive used throughout the world. But black powder, or gun powder as it was commonly called, produced a large amount of smoke and was dangerous to use. Today black powder is still used for pyrotechnics (fireworks), special effects, and other specialized work, but it has been replaced in commercial blasting by safer, more productiveexplosive materials.
High explosives create more pressure and burn more quickly, detonating almost instantaneously. The proper use of high explosives by today’s explosives engineer, produces minimal ground vibrations and air overpressure.
The first high explosive used in commercial blasting was nitroglycerine, also called "blasting oil." Nitroglycerine was dangerous to use because itis an unstable chemical. But in the late 1800’s, a Swedish chemist, named Alfred Nobel, invented dynamite by mixing nitroglycerine with a special clay, called kieselghur, and packed it into sticks.
Dynamite became the first safe high explosive used. It can be dropped, hit with a hammer or even burned and will not accidentally explode. There are a number of different types of dynamites being usedtoday, all containing nitroglycerine.
Different Types of Detonators
Blasting caps come in a variety of forms. Fuse caps, electric detonators, non-electric detonators and electronic detonators are the different types of detonators you can find on the market.
The invention of the successive generations of fuse caps aims to answer the hazardous ignition of the explosivesproduct used during the considered period. Miners’ safety has always been one of the main objectives in blasting accessories development.
Being very cheap, fuse caps are still widely used today in the mining industry, especially in developing countries. Fuse caps are also, by design, insensitive to electromagnetic fields.
The first prototypes of detonators usingelectricity as an initiation signal energy source emerged in the late 1880s.
Electric blasting caps are similar to fuse caps, but with two insulated electric wires protruding from one end, instead of the fuse.
The inclusion of a delay powder train allowed the introduction of pre-programmed electric delayed detonators. This technology allows an offset between two consecutive charges and...
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