Explosive primer redirects here.
A blasting cap is a small explosive device generally used to detonate a larger, more powerful explosive such as dynamite. An explosive material is a material that either is chemically or otherwise Energetically unstable or produces a sudden expansion of the material usually accompanied For the Ratt album see Detonator (album A detonator is a device used to trigger an Explosive device. An explosive material is a material that either is chemically or otherwise Energetically unstable or produces a sudden expansion of the material usually accompanied Dynamite is an explosive based on the explosive potential of Nitroglycerin, initially using Diatomaceous earth (kieselgur US Spelling kieselguhr
Blasting caps come in a variety of types, some of which are: non-electric caps, electric caps and fuse caps. They are used in commercial mining and are set off by a dynamo device which generates a short burst of current in a line long enough to ensure safety. Mining is the extraction of valuable Minerals or other geological materials from the earth usually (but not always from an Ore body A dynamo, originally another name for an Electrical generator, now means a generator that produces Direct current with the use of a commutator.
The need for blasting caps arises due to sensitivity issues of an explosive compound. All explosive compounds have a certain amount of energy required to create detonation. If an explosive is too sensitive, it may go off unexpectedly, and so the most practical explosive compound is one that is safe to handle and won't explode if accidentally dropped or mishandled. However, such explosives are hard to initiate intentionally as well. A blasting cap contains an easy-to-ignite explosive that provides the initial activation energy to start a detonation in a more stable explosive. In Chemistry, activation energy, also called midnight energy, is a term introduced in 1889 by the Swedish scientist Svante Arrhenius, that is defined
Most blasting caps contain what is called a primary explosive. Primary and secondary are the two distinct classifications of Explosives. A primary explosive is a high explosive compound that will explode from flame, heat or shock. An explosive material is a material that either is chemically or otherwise Energetically unstable or produces a sudden expansion of the material usually accompanied A blasting cap may also contain a booster – another explosive to make the cap more powerful, and thus more reliable for detonating secondary explosives. An explosive booster acts as a bridge between a low energy Explosive and a low sensitivity (but typically high energy explosive
Explosives commonly used in blasting caps include mercury fulminate, sodium azide, lead azide, and tetryl. Mercury(II fulminate, Hg(CNO2 is a Primary explosive. It is highly sensitive to Friction and shock. Sodium azide is the Chemical compound with the formula NaN3 This colourless Azide salt is a common reagent in Organic Lead azide ( Pb ( N 32 is an Explosive and Toxic crystalline compound Tetryl is a sensitive Explosive compound used to make Detonators and Explosive booster charges
Because of their size and appearance, blasting caps are sometimes not recognized as explosives, leading to injuries.
Contents |
Types of Blasting Caps
Pyrotechnic Fuse Blasting Caps
The oldest and simplest type of cap, fuse caps are a metal cylinder, closed at one end. From the open end inwards, there is first an empty space into which a pyrotechnic fuse is inserted and crimped, then a pyrotechnic ignition mix, a primary explosive, and then the main detonating explosive charge. Primary and secondary are the two distinct classifications of Explosives.
The primary hazard of pyrotechnic blasting caps is that for proper usage, the fuse must be inserted and then crimped into place by crushing the base of the cap around the fuse. If the tool used to crimp the cap is used too close to the explosives, the primary explosive compound can detonate during crimping. A common hazard is unsafe blasters crimping caps with their teeth; an accidental detonation can cause serious or fatal injuries to the mouth and head. Proper recommended procedure is to position the crimping tool and tighten it up, then hold it behind oneself slightly below waist level while actually crimping. While embarrassing, minor injuries to the buttocks are the location least likely to cause serious or permanent incapacitation.
Fuse type blasting caps are still in active use today. They are the safest type to use around certain types of electromagnetic interference, and they have a built in time delay as the fuse burns down.
Solid Pack Electric Blasting Cap
Solid pack electric blasting caps use a thin bridge wire in direct contact (hence solid pack) with a primary explosive, which is heated by electric current and causes the detonation of the primary explosive. That primary explosive then detonates a larger charge of secondary explosive.
Some solid pack fuses incorporate a small pyrotechnic delay element, up to a few hundred milliseconds, before the cap fires.
Match or Fusehead Electric Blasting Cap
Match type blasting caps use an electric match (insulating sheet with electrodes on both sides, a thin bridgewire soldered across the sides, all dipped in ignition and output mixes) to initiate the primary explosive, rather than direct contact between the bridge wire and the primary explosive. The match can be manufactured separately from the rest of the cap and only assembled at the end of the process.
Match type caps are now the most common type found worldwide.
Exploding Bridgewire Detonator or Blasting Cap
This type of detonator was invented in the 1940s as part of the Manhattan project to develop nuclear weapons. The exploding-bridgewire detonator ( EBW, also known as exploding wire detonator) was invented by Luis Alvarez and Lawrence Johnson for the The World War II Manhattan Project developed the first Nuclear weapon (atomic bomb The design goal was to produce a detonator which acted very rapidly and predictably. Both Match and Solid Pack type electric caps take a few milliseconds to fire, as the bridge wire heats up and heats the explosive to the point of detonation. Explosive bridgewire or EBW detonators use a higher voltage electric charge and a very thin bridge wire (1 mm long, 0. 04 mm diameter). Instead of heating up the explosive, the EBW detonator wire is heated so quickly by the high firing current that the wire actually vaporizes and explodes due to electric resistance heating. That electrical driven explosion then fires the detonator's initiator explosive (usually PETN). Pentaerythritol tetranitrate ( PETN, also known as pentrite, or rarely and primarily in German as nitropenta) is one of the most powerful high explosives
Some similar detonators use a thin metal foil instead of a wire, but operate in the same manner as true bridgewire detonators.
In addition to firing very quickly when properly activated, EBW detonators are safe from stray static electricity and other electrical current. Enough current and the bridge wire may melt, but it is small enough that it cannot detonate the initiator explosive unless the full, high voltage high current charge passes through the bridgewire. EBW detonators are used in many civilian applications where radio signals, static electricity, or other electrical hazards might cause accidents with conventional electric detonators.
Slapper Detonator or Blasting Cap
Slapper detonators are an improvement on EBW detonators. A slapper detonator is a relatively recent kind of a Detonator developed in Lawrence Livermore National Laboratory. Slappers, instead of directly using the exploding foil to detonate the initiator explosive, use the electrical vaporization of the foil to drive a small circle of insulating material such as PET film or kapton down a circular hole in an additional disc of insulating material. Biaxially-oriented Polyethylene terephthalate (boPET Polyester film is used for its high Tensile strength, Chemical and dimensional Stability Kapton ® is a Polyimide film developed by DuPont which can remain stable in a wide range of temperatures from -269 °C to +400 °C (4 K - 673 K At the far end of that hole is a pellet of conventional initiator explosive.
The conversion efficiency of energy from electricity into kinetic energy of the flying disk or slapper can be 20-40%.
Since the slapper impacts a wide area (roughly one mm across) of the explosive, rather than a thin line or point as in an exploding foil or bridgewire detonator, the detonation is more regular and requires less energy. Reliable detonation requires raising a minimum volume of explosive to temperatures and pressures at which detonation starts. If energy is deposited at a single point, it can radiate away in the explosive in all directions in rarefaction or expansion waves, and only a small volume is efficiently heated or compressed. The flyer disc loses impact energy at its sides to rarefaction waves, but a conical volume of explosive is efficiently shock compressed.
Slapper detonators are used in nuclear weapons. A nuclear weapon is an explosive device that derives its destructive force from Nuclear reactions either fission or a combination of fission and fusion. These components require large quantities of energy to initiate, making them extremely unlikely to accidentally discharge.
Laser Ordnance Initiators
Another type of initiator that is rarely seen requires the use of a laser to initiate a carbon-doped explosive via a fiber optic. A laser is a device that emits Light ( Electromagnetic radiation) through a process called Stimulated emission. An optical fiber (or fibre) is a Glass or Plastic fiber that carries Light along its length These initiators are highly reliable, and offer a number of advantages, primarily in that unintentional initiation is made very difficult. Without the correct laser initiation system, or a completely independent initiation system, these components are not capable of being controlled remotely.
History
The first blasting cap or detonator was demonstrated in 1745, when a Dr. Year 1745 ( MDCCXLV) was a Common year starting on Friday (link will display the full calendar of the Gregorian calendar (or a Watson of the Royal Society showed that the electric spark of a Leyden Jar could ignite black powder. The Royal Society of London for the Improvement of Natural Knowledge, known simply as The Royal Society, is a Learned society for science that was founded in 1660 The Leyden jar is a simple device that "stores" static electricity in large amounts
In 1750, Benjamin Franklin in Philadelphia made a commercial blasting cap consisting of a paper tube full of black powder, with wires leading in both sides and wadding sealing up the ends. Year 1750 ( MDCCL) was a Common year starting on Thursday (link will display the full calendar of the Gregorian calendar (or a Benjamin Franklin ( April 17 1790 was one of the Founding Fathers of the United States of America. Gunpowder is a an explosive mixture of Sulfur, Charcoal and Potassium nitrate (also known as saltpetre/saltpeter that burns rapidly producing volumes The two wires came close but did not touch, so a large electric spark discharge between the two wires would fire the cap.
In 1822 the first hot wire detonator was produced by Dr Robert Hare. Year 1822 (MDCCCXXII was a Common year starting on Tuesday (see link for calendar of the Gregorian calendar (or a Common year starting on Sunday of the Using one strand separated out of a multistrand wire as the hot bridge wire, this blasting cap ignited a pyrotechnic mixture (believed to be potassium chlorate/arsenic/sulphur) and then a charge of tamped black powder.
In 1864, Alfred Nobel introduced the first Pyrotechnic Fuse blasting cap, using mercury fulminate to detonate dynamite. Year 1864 ( MDCCCLXIV) was a Leap year starting on Friday (link will display the full calendar of the Gregorian Calendar (or a Leap year (21 October 1833 Stockholm, Sweden – 10 December 1896 Sanremo, Italy) was a Swedish chemist engineer innovator armaments manufacturer Mercury(II fulminate, Hg(CNO2 is a Primary explosive. It is highly sensitive to Friction and shock. Dynamite is an explosive based on the explosive potential of Nitroglycerin, initially using Diatomaceous earth (kieselgur US Spelling kieselguhr In 1868, H. Year 1868 ( MDCCCLXVIII) was a Leap year starting on Wednesday (link will display the full calendar of the Gregorian Calendar (or a Leap Julius Smith introduced a cap that combined a spark gap ignitor and mercury fulminate, the first electric cap able to detonate dynamite.
In 1875, Perry "Pell" Gardiner and Smith independently developed and marketed caps which combined the hot wire detonator with mercury fulminate explosive. Year 1875 ( MDCCCLXXV) was a Common year starting on Friday (link will display the full calendar of the Gregorian calendar (or a Common These were the first generally modern type blasting caps. Modern caps use different explosives and separate primary and secondary explosive charges, but are generally very similar to the Gardiner and Smith caps.
Electric match caps were developed in the early 1900s in Germany, and spread to the US in the 1950s when ICI International purchased Atlas Powder Co. Imperial Chemical Industries ( ICI) is a British chemical subsidiary of a Dutch conglomerate and one of the largest chemical producers These match caps have become the predominant world standard cap type.
External links
- Blaster Exchange Explosives Industry Portal
- Old safety film for children on the dangers of blasting caps from Prelinger Archives
References
Cooper, Paul W. The Prelinger Archives is a collection of Films relating to U , Explosives Engineering, New York: Wiley-VCH, 1996. ISBN 0-471-18636-8
Dapyx Software network: MP3 Explorer | Ebook Manager | Zenithic