Different Types of Detonators Used in Mining
A detonator is a fuse or a device used to make a substance or a bomb explode. When explosives were in its early development stage, burning fuses were used to delay the ignition of the explosive until the person lighting the fuse could get to a safe distance.
Detonators are also known as blasting caps, which have evolved into many 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 explosives product used during the considered period. Miners’ safety has always been one of the main objectives of blasting accessories development.
Black powder is traditionally believed to be a Chinese invention. Despite the use of black powder-based “Greek-fires” in ancient battles,1380 is a commonly acknowledged date for the first uses of black powder. German Franciscan Monk, Berthold Schwarts, developed gunpowder from the antique formula. The first recorded use of black powder for rock blasting dates back to 1627, in Hungary.
It's unreliable burning speed nevertheless made black powder extremely dangerous and resulted in many accidents and deaths. The dangerous ignition process was overcome with the introduction the "Miners Safety Fuse" in 1831, which is a rope with a strand of yarn infused with black powder.
Nitroglycerin was discovered in 1846 and was the first explosive that was more powerful than black powder. However, it was extremely dangerous until 1863 when Alfred Nobel unveiled his "practical detonator." The detonator was a metal shell containing a wooden plug of black powder placed in a charge of liquid nitroglycerin. Eventually, Nobel developed a mercury blasting cap. Mercury is highly sensitive to friction and heat and acts as a primary explosive to ignite a substance such as black powder.
Fuse caps are relatively inexpensive and as a result, are still widely used today in the mining industry, especially in developing countries. Fuse caps are also, by design, insensitive to electromagnetic fields.
Electric blasting caps are similar to fuse caps, but with two insulated electric wires protruding from one end, instead of the fuse. With an electric detonator, a small charge is sent to the detonator cap through a small cord and ignites an explosive material.
Instantaneous electric detonators allow the ignition through a mercury fulminate mixture, a high-resistance platinum bridge wire, and a sulfur plug. 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 therefore, the creation of initiation sequences, opening doors to more controlled shots but limited to a finite number of combinations.
Electric detonators are sensitive to heat, shock, static electricity, radio frequency energy, and electromagnetic radiation.
Total non-electric initiation systems were introduced to offer all the advantages of electric initiation but adding safety benefits including insensitivity to electricity, radio frequency energy, and electromagnetic radiation. Non-electric detonators also improved operational flexibility because of their easier to design larger initiation sequences, theoretically with an unlimited number of delays.
This initiation system is composed of shock tubes connected to down-the-hole detonators and surface connectors. Though their coating of reactive powders and thanks to a starter, shock tubes transmit shock waves to the non-electric detonators. Non-electric detonators are used worldwide.
Electric detonators use a microchip, which is located in the plug and when triggered electronically, the energy from the capacitor ignites the fuse head.
The electronic developments make the creation of a sequential blasting machine possible. The sequential blasting machine delivers electronically adjustable timed bursts of energy to a number of lead wires, dramatically increasing the maximum number of electric detonators. The blasters can connect and therefore increase the number of potential combinations.
Enormous research and development has been conducted to develop pre-programmed or programmable electronic detonators. Programmable electronic detonators represent a step ahead in the logic, offering amazing flexibility in the choice of initiation timing. This flexibility together with the electronically controlled accuracy opens doors for short delays complex initiation sequences that have since demonstrated significant benefits (nuisance reduction, productivity increase) to mining stakeholders. Numerical simulation software tools have been developed to help mining engineers to deal with such a huge number of possibilities in the design of their shots.
Despite a higher market price, electronic detonators steadily spread on the market during the 2000s. A strong merger and acquisition stage has resulted in the disappearance of a large portion of the manufacturers. Nowadays, only 5 or 6 manufacturers remain active in this market.
Each brand can be programmed only by its own specifically designed blasting machine. Due mainly to different communication protocols, none of these machines can be used to initiate several brands of detonators. Consequently, none of these brands can be mixed in a single shot.
The first wireless blasting machine appeared on the market in 2000, allowing the initiation of bigger shots from a safer distance. Wireless initiation has become a standard on the market. Electronic detonators are still based on electrical wiring to conduct the initiation signal energy source. Wireless detonators aim to improve on the operational weaknesses of electronic detonators such as potential leakage, shorts, cut-off, and electromagnetic sensitivity. With each development in detonator technology, mine safety, productivity, and profitability is likely to improve.