Triggering sequence
Encyclopedia
A triggering sequence, also called an explosive train, is a sequence of events that culminates in the detonation
of explosives. For safety reasons, most widely used high explosives are difficult to detonate. A primary explosive of higher sensitivity is used to trigger a uniform and predictable detonation of the main body of the explosive. Although the primary explosive itself is generally a more sensitive and expensive compound, it is only used in small quantities and in relatively safely packaged forms. By design there are low explosives and high explosives made such that the low explosives are highly sensitive (i.e. their 'Figure of Insensitivity' is low) and high explosives are comparatively insensitive. This not only affords inherent safety to the usage of explosives during handling and transport, but also necessitates an explosive triggering sequence or explosive train. The explosive triggering sequence or the explosive train essentially consists of an 'initiator', an 'intermediary' and the 'high explosive'.
For example, a match will not cause plastic explosive
to explode, but it will light a fuse which will detonate a primary explosive that will shock a secondary high explosive and cause it to detonate. In this way, even very insensitive explosives may be used; the primary detonates a "booster" charge that then detonates the main charge. Triggering sequences are used in the mining industry for the detonation of ANFO
and other cheap, bulk, and insensitive explosives that can not be fired by only a blasting cap
or similar item.
and dynamite
) or three-step (e.g., detonator, booster
of primary explosive, and main charge of secondary explosive).
Detonators are often made from tetryl
and fulminate
s.
Examples of bursting charges are
The most significant tertiary material in wideaspread use is ANFO
.
Detonator
A detonator is a device used to trigger an explosive device. Detonators can be chemically, mechanically, or electrically initiated, the latter two being the most common....
of explosives. For safety reasons, most widely used high explosives are difficult to detonate. A primary explosive of higher sensitivity is used to trigger a uniform and predictable detonation of the main body of the explosive. Although the primary explosive itself is generally a more sensitive and expensive compound, it is only used in small quantities and in relatively safely packaged forms. By design there are low explosives and high explosives made such that the low explosives are highly sensitive (i.e. their 'Figure of Insensitivity' is low) and high explosives are comparatively insensitive. This not only affords inherent safety to the usage of explosives during handling and transport, but also necessitates an explosive triggering sequence or explosive train. The explosive triggering sequence or the explosive train essentially consists of an 'initiator', an 'intermediary' and the 'high explosive'.
For example, a match will not cause plastic explosive
Plastic explosive
Plastic explosive is a specialised form of explosive material. It is a soft and hand moldable solid material. Plastic explosives are properly known as putty explosives within the field of explosives engineering....
to explode, but it will light a fuse which will detonate a primary explosive that will shock a secondary high explosive and cause it to detonate. In this way, even very insensitive explosives may be used; the primary detonates a "booster" charge that then detonates the main charge. Triggering sequences are used in the mining industry for the detonation of ANFO
ANFO
ANFO is a widely used bulk industrial explosive mixture. It consists of 94 percent porous prilled ammonium nitrate , that acts as the oxidizing agent and absorbent for the fuel — six percent Number 2 Fuel Oil...
and other cheap, bulk, and insensitive explosives that can not be fired by only a blasting cap
Blasting cap
A blasting cap is a small sensitive primary explosive device generally used to detonate a larger, more powerful and less sensitive secondary explosive such as TNT, dynamite, or plastic explosive....
or similar item.
Low Explosive Train
An example of a low-explosive train is a rifle cartridge, which consists of- a primer consisting of a small amount of primary high explosive which initiates the explosive train
- an igniter which is initiated by the primer and creates a flame that ignites the propellant
- a propellantPropellantA propellant is a material that produces pressurized gas that:* can be directed through a nozzle, thereby producing thrust ;...
consisting of a secondary low explosive that emits a large amount of gas as it deflagratesDeflagrationDeflagration is a term describing subsonic combustion that usually propagates through thermal conductivity; hot burning material heats the next layer of cold material and ignites it. Most "fire" found in daily life, from flames to explosions, is deflagration...
.
High Explosive Train
High-explosives trains can be either two-step (e.g., detonatorDetonator
A detonator is a device used to trigger an explosive device. Detonators can be chemically, mechanically, or electrically initiated, the latter two being the most common....
and dynamite
Dynamite
Dynamite is an explosive material based on nitroglycerin, initially using diatomaceous earth , or another absorbent substance such as powdered shells, clay, sawdust, or wood pulp. Dynamites using organic materials such as sawdust are less stable and such use has been generally discontinued...
) or three-step (e.g., detonator, booster
Explosive booster
An explosive booster acts as a bridge between a low energy explosive and a low sensitivity explosive such as TNT. It increases the explosive shockwave from an initiating explosive to the degree sufficient to detonate the secondary charge.Unlike C4 plastic explosive, not all explosives can be...
of primary explosive, and main charge of secondary explosive).
Primary components
A high explosive train includes three primary high explosive components which are used to initiate explosives:- FuseFuse (explosives)In an explosive, pyrotechnic device or military munition, a fuse is the part of the device that initiates function. In common usage, the word fuse is used indiscriminately...
or fuzeFuzeFuze Beverage, commercially referred to as just Fuze , is a manufacturer of teas and non-carbonated fruit drinks enriched with vitamins. Currently the brand consists of five vitamin-infused lines: Slenderize, Refresh, Tea, Defensify, and Vitalize... - Primer
- DetonatorDetonatorA detonator is a device used to trigger an explosive device. Detonators can be chemically, mechanically, or electrically initiated, the latter two being the most common....
Detonators are often made from tetryl
Tetryl
2,4,6-Trinitrophenylmethylnitramine commonly referred to as tetryl is a sensitive explosive compound used to make detonators and explosive booster charges....
and fulminate
Fulminate
Fulminates are chemical compounds which include the fulminate ion. The fulminate ion, is a pseudohalic ion, acting like a halogen with its charge and reactivity. Due to the instability of the ion, fulminate salts are friction-sensitive explosives. The best known is mercury fulminate, which has...
s.
Secondary components
In an explosive train there are two secondary high explosive components:- BoosterExplosive boosterAn explosive booster acts as a bridge between a low energy explosive and a low sensitivity explosive such as TNT. It increases the explosive shockwave from an initiating explosive to the degree sufficient to detonate the secondary charge.Unlike C4 plastic explosive, not all explosives can be...
s - Bursting charges, also known as main charges
Examples of bursting charges are
- TNT
- Composition BComposition BComposition B, colloquially "comp B", is an explosive consisting of castable mixtures of RDX and TNT. It is used as the main explosive filling in artillery projectiles, rockets, land mines, hand grenades, sticky bombs and various other munitions...
- RDXRDXRDX, an initialism for Research Department Explosive, is an explosive nitroamine widely used in military and industrial applications. It was developed as an explosive which was more powerful than TNT, and it saw wide use in WWII. RDX is also known as cyclonite, hexogen , and T4...
- PETNPETNPentaerythritol tetranitrate , also known as PENT, PENTA, TEN, corpent, penthrite , is the nitrate ester of pentaerythritol. Penta refers to the five carbon atoms of the neopentane skeleton.PETN is most well known as an explosive...
Tertiary compments
In some cases, the main charge is so insensitive that using typical primary materials becomes impractical due to large amount required. Thus, an explosive booster is used to deliver sufficient shockwave to the main charge.The most significant tertiary material in wideaspread use is ANFO
ANFO
ANFO is a widely used bulk industrial explosive mixture. It consists of 94 percent porous prilled ammonium nitrate , that acts as the oxidizing agent and absorbent for the fuel — six percent Number 2 Fuel Oil...
.