An explosive is any chemical compound that is capable of undergoing instantaneous detonation under the supply of an impulse (high VOD shock wave) like fire, lightening, heat, friction, shock. Such compound at the point of detonation releases high energetic shock and gas energy which result into Explosion (increase in volume) under an exothermic reaction. Explosive energy can be hazardous big not properly managed. Explosives are only design for war (military) and peace (Mining) other usage (terrorist) is assumed to be illegal.
Explosive in 1627 was know only within the use of black powder for the fragmentation of rock mass into smaller size. The idea of breaking rock with Explosive was start in Hungary in year 1627 February.
Rock mass is a solid mineral Resources containing various mineral grains bonded together by cementing minerals like calcite, gypsum, quartz. This high strength bond between rock grains makes it more difficult to fragment in the 1500s. Thou inventory of Explosive into mining for blasting diver ways of rock breaking was identified with the Egyptians in Bible story.
The use of thermal expansion principle, use of impact load, chiseling approach and collision were some of the ways Stone age miners gets their rock mass fragmented. Even biblically during the building of Solomon temple in the city of Jerusalem, the king assign strong men to the quarry to get boulders for the building foundation.Therefore, use of Explosive as a means of breaking rock appears as a great solution to humanity problem. Explosive genealogy was traced from black powder which was claimed to be first used in China for fire walks to pulminating gold, pulminating mercy.
Then down to the Liquid Explosive called Nitroglycerin (NG). This NG is a liquid Explosive with high sensitivity. It sensitive to shock and therefore highly dangerous. During the time of Nitroglycerin Explosive various scholars like Alfred Nobel and others alongside with his brother work on how to make this Explosive chemical industrially safe for usage, handling, and transportation. During one of those days, Nobel brother ?Emil) alongside with others were killed by explosion accident on the base of Nitroglycerin Explosive in one of Alfred Nobel Laboratory.
At that period, charge drill hole with NG is something done with great fear and trembling. A view on how this was done shows that, the Nitroglycerin Explosive (in a bottle) is lower gently into the how with a thread or rope. Any mistake of suddenly drop of the bottle result into instantaneous detonation which will factually claim the life of the blasters men. This becomes a great challenge to the mining Engineers, a great challenge to the Explosive producing companies and a great issue to blasters.
Thou after black powder was used in mining industry for 227 years, due to it limit in shock wave energy, gun gotten was invented in 1854 but the use was stopped immediately.Nitroglycerin was invented by Sobrero in 1846 as a medicine for Angina pectoris, before Alfred Nobel decided to work on combining Nitroglycerin with Kieselguhr to produce Nitroglycerin dynamite in sweden year 1865. Later Alfred Nobel further his research on gun cotten by combining gun cotten and Nitroglycerin to produce Gelatin Dynamite Explosive. These Explosive products then we're highly expensive and was weathering mining profit margin.
In 1950's ANFO (Ammonium Nitrate and Fuel oil) was invented. This was a great move in mining industry phase as the challenge of cost implication on Explosive was solved and lighten. The only issue was the water resistance challenge. ANFO become insensitive and become hazardous (possiblity of misfire) when use in a watery environment. From year 1979 to 1980's, the invention of other Explosives like slurries and water gel Explosive were achieved to solve the problem of water resistance.
Many life's have been claimed by Explosive inventory from 1627 to 1980's.
For the sake of people who are not associated with mining field. Blasting is done by drilling a hole, charging the hole with a specified Explosive quantity, connecting the blastholes with shock sensitive connecting cortex cords. After which shock wave from surface (cap and fuse for NONEL or exploder for electric) is release to initiate the downline Explosive primer and column charge.
The major challenge in 1969's was how to initiate the Explosive after loading it into the drill holes. The Explosive is highly sensitive, it detonates instantaneously, it requires specified shock energy to distinguished detonation from burning.
Thou many approaches were used earlier but all were lacking high confidence in safety.
This call for the invention of Blasting accessories by Alfred Nobel in 1960's.
Although before then the Explosives have been worked on a bit to sensitize division into low and high Explosive. This brought about the classification of Explosive into those that are highly sensitive to impulse and those that are not.
This classification was done base on the Velocity of detonation of each Explosive which dictates the gas pressure release at initiation. All this was done to ensure safety is garantee.
After the incident that lead to the death of Nobel's brother during the invention of Nitroglycerin in 1840's, the idea of limiting the sensitivity of high VOD Explosive to specified shock energy and it distinct classification becomes interesting so as to aid SAFETY level at storage, usage and transportation. Most precautions attached to Explosive storage, transportation and handling were discovered through experiences that lead to lost of many innocent life. Let take a brief look at the classification breakdown and see the key elements that support the classification.
High and low Explosive: well I'm fully aware that this classification was done in a bit to ensure instant Explosion of Explosive material at drop, accidental throw is controlled. NG the killer Explosive during inventory left many scary experience like accidental drop during mixture, packing, transportation, storage which claim many life. Highly sensitive Explosive (primary Explosive rich chemicals) were not just sensitive to small shock but can accommodate and amplify small shock. The fact that at the encounter of primary Explosive with infinitesimal shock energy can produce magnified explosion makes inventors to call for a new way of ensuring safety.
Differentiation between High and low Explosive
High Explosives are those with high Velocity of detonation, highly sensitive to shock energy or friction (undergo detonation), at destination release larhe amount of shock energy wave faster than the speed of sound (1200-9000 meters per second). This type of Explosive are known to be supply high detonation pressure than the low Explosive.
Prove:
Detonation pressure=(Explosive density*VOD^2)/4
Example of high Explosive are; Nitroglycerin, TNT, PETN.
Low Explosives are those with low VOD which at initiation with less shock undergo deflagration (burning) rather than detonation. Low Explosives are characterised by the release of only gas pressure at initiation. They released wave with speed lesser than the speed of sound (less than 2000 meters per second).
Example of low Explosive is ANFO, thou in most critical time, scholars tend to classify ANFO as blasting agent, but still is still year back to low Explosive.
Another thing that differentiate low and high Explosive is the ability of high Explosive to detonate under the shock wave supply by cap number 8 containing (0.125g lead azide and 0.78g PETN).
Blasting Accessories in view
These accessories are additional materials use along side with exploy to achieve blasting. The accessories are subordinate agents that create the required atmosphere needed for Explosive to function in the loop of explosion.
This was started by Alfred Nobel in 1960's after inventing his first Nitroglycerin dynamite. He make use of pan and black powder to create the first cap with the intention of creating means to have a safe distance between the time of initiation and detonation.
He invented safety fuse and cap for mining purpose in 1960's.
This tend to solve the issue of instantaneous detonation which limited the extent to which Explosive can be use for mining purpose. With this safety fuse and cap, large charged holes can be detonated at a safe time without the fire man appearance at the blast site.
The safety fuse recieve impulse from the fire person, take sufficient time to transmit the impulse to the cap which detonation (0.125-0.2g) of primary Explosive for the release of shock energy about 3200+ m/s to the primer and column charge through the detonating cord.
The invention of safety fuse, cap/detonator, connecting cords was a new phase of development in 1957-1970's.
Other blasting accessories use in blasting are: cortex cord, shock tube, surface delay, electric detonator, electronic detonator, exploder, clips, booster, to mention few.
My next article will cover safety Tips in Explosive handling, transportation, storage and usage.
You can access the video clip on my Facebook page (Mining Knowledge/Experience: GIANT MINER).
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