Detonator

top: small nonel detonator with 25ms delay for chaining nonel tubes, middle: class B SPD detonator, bottom: class C SPD detonator

Inserting detonators into blocks of C-4 explosive

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.

The commercial use of explosives uses electrical detonators or the capped fuse which is a length of safety fuse to which an ordinary detonator has been crimped. Many detonators' primary explosive is a material called ASA compound. This compound is formed from lead azide, lead styphnate and aluminium and is pressed into place above the base charge, usually TNT or tetryl in military detonators and PETN in commercial detonators.

Other materials such as DDNP (diazo dinitro phenol) are also used as the primary charge to reduce the amount of lead emitted into the atmosphere by mining and quarrying operations. Old detonators used mercury fulminate as the primary, often mixed with potassium chlorate to yield better performance.

Types

Ordinary detonators

Ordinary detonators usually take the form of ignition-based explosives. Whilst they are mainly used in commercial operations, ordinary detonators are still used in military operations. This form of detonator is most commonly initiated using safety fuse, and used in non time-critical detonations e.g. conventional munitions disposal. Well known detonators are lead azide, Pb(N₃)₂, silver azide (AgN₃) and mercury fulminate [Hg(ONC)₂].

Electrical detonators

There are three categories of electrical detonators: instantaneous electrical detonators (IED), short period delay detonators (SPD) and long period delay detonators (LPD). SPDs are measured in milliseconds and LPDs are measured in seconds. In situations where nanosecond accuracy is required, specifically in the implosion charges in nuclear weapons, exploding-bridgewire detonators are employed. The initial shock wave is created by vaporizing a length of a thin wire by an electric discharge. A new development is a slapper detonator, which uses thin plates accelerated by an electrically exploded wire or foil to deliver the initial shock. It is in use in some modern weapon systems. A variant of this concept is used in mining operations, when the foil is exploded by a laser pulse delivered to the foil by optical fiber.

Non electric detonators

Non electric detonators is a shock tube detonator designed to initiate explosions, generally for the purpose of demolition of buildings and for use in the blasting of rock in mines and quarries. Instead of electric wires, a hollow plastic tube delivers the firing impulse to the detonator, making it immune to most of the hazards associated with stray electric current. It consists of a small diameter, three-layer plastic tube coated on the innermost wall with a reactive explosive compound, which, when ignited, propagates a low energy signal, similar to a dust explosion. The reaction travels at approximately 6,500 ft/s (2,000 m/s) along the length of the tubing with minimal disturbance outside of the tube. The design of Non electric detonators incorporates patented technology, including the Cushion Disk (CD) and Delay Ignition Buffer (DIB) to provide reliability and accuracy in all blasting applications. Non electric detonators was invented by the Swedish company Nitro Nobel in the 1960s and 1970s,[1] under the leadership of Per-Anders Persson,[2] and launched to the demolitions market in 1973.[3] (Nitro Nobel became a part of Dyno Nobel after being sold to Norwegian Dyno Industrier AS in 1986.) Nonel is a contraction of "Non electric detonators".[4]

Electronic detonators

In civil mining, electronic detonators have a better precision for delays. Electronic detonators are designed to provide the precise control necessary to produce accurate and consistent blasting results in a variety of blasting applications in the mining, quarrying, and construction industries. electronic detonators may be programmed in 1-millisecond increments from 1 millisecond to 10 000 milliseconds using the dedicated programing device called the logger.

Benefits:

• 100% verification of reliability of connections in initiation network.
• Delay range of 1- 10 000 ms with an increment of 1 ms. DigiShot delay range is up to 20 000 ms^[1]
• Precision of 0.01% of nominal delay time.
• Safe and reliable initiation of up to 1600 units in one blast per one blasting machine.
• Unique ID in each detonator.
• Multiple verification of detonators prior each blast.

Fictional variations

• G-4 detonator, in Battlestar Galactica
• Ion detonator, in the video game Destroy All Humans!
• Mk2 detonator, in the video game GoldenEye: Rogue Agent
• Thermal detonator, in the film series Star Wars

See also

Wikimedia Commons has media related to Detonators.

References