What is an explosion? This is the process of instantly transforming the state of an explosive, in which a significant amount of thermal energy and the gases that form the shock wave are released.
Explosives are compounds with the ability to undergo changes in the physical and chemical state as a result of external exposure with the formation of an explosion.
Explosion Type Classification
1. Physical - explosion energy is the potential energy of a compressed gas or vapor. Depending on the magnitude of the internal energy pressure, an explosion of various powers is obtained. The mechanical effect of the explosion is due to the action of the shock wave. Shell debris causes an additional damaging effect.
2. Chemical - in this case, the explosion is caused by almost instantaneous chemical interaction of the substances in the composition, with the release of a large amount of heat, as well as gases and steam with a high degree of compression. Explosions of these types are characteristic, for example, for gunpowder. Substances arising as a result of a chemical reaction acquire a lot of pressure when heated. An explosion of pyrotechnics also belongs to this species.
3. Atomic explosions are lightning-fast reactions of nuclear fission or fusion, characterized by a huge power of released energy, including thermal. The colossal temperature in the epicenter of the explosion leads to the formation of a zone of very high pressure. The expansion of the gas leads to the appearance of a shock wave, which is the cause of mechanical damage.
The concept and classification of explosions allows you to act correctly in an emergency.
Action type
Explosives by type of action are classified into the following types:
- condensed;
- voluminous.
The first type is such compounds, which, being under normal conditions in a solid or liquid state of aggregation, can, under external influence, begin the transformation reaction, accompanied by the appearance of superheated vapors and gases with the formation of a stable high-pressure zone. A sharp expansion of the gaseous medium leads to shock. Such reactions are called explosive transformation.
To start the reaction, it is necessary to give explosives some initial energy of a mechanical, thermal, electrical, chemical or other type.
Explosive groups
There are three main groups of condensed explosives.
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The properties |
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I |
Particularly dangerous explosives. They are prone to conversion reactions, unstable. The danger is even in small quantities. Examples: copper (I) acetylenide, nitrogen trichloride. |
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II |
Primary explosives. More stable compared to group I. Easily detonated from mechanical or thermal effects from the outside. Often used in detonators. Examples: lead azide, mercury (II) fulminate. |
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III |
Secondary explosives. The initiation of an explosion occurs only with a strong external impact, for example, from detonation. Relatively stable and provide long-term storage, possibly warehousing. Examples: dynamite, TNT. |
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IV |
Powder Explosions are very stable, react poorly to external mechanical stress. Initiated by heat. Depending on the environmental conditions, they may burn or explode (in the case of a closed loop). |
Distinctive features
Explosions vary depending on the ongoing chemical reactions:
- Decomposition is characteristic of a gaseous medium.
- Redox processes imply the presence of a reducing agent with which oxygen in the air will react.
- The reaction of mixtures.
Volumetric explosions include dust explosions, as well as explosions of steam clouds.
Dust explosions
They are characteristic of closed dusty structures, such as mines. A hazardous concentration of explosive dust occurs during mechanical work with bulk materials that produce a large amount of dust. Working with explosive substances requires a thorough knowledge of what an explosion is.
For each type of dust there is a so-called maximum permissible concentration, above which there is a danger of spontaneous explosion, and this amount of dust is measured in grams per cubic meter of air. The calculated concentration values are not constant values and should be adjusted depending on humidity, temperature and other environmental conditions.
Of particular danger is the presence of methane. In this case, there is an increased probability of detonation of dust mixtures. Already a five percent methane vapor content in the air threatens to explode, due to which ignition of the dust cloud and increased turbulence follow. There is a positive feedback, leading to an explosion of high energy. Scientists are attracted to such reactions, the explosion theory still haunts many.
Safety when working in confined spaces
When working in confined spaces with a high dust content in the air, the following safety rules must be followed:
- dust removal by ventilation;
- fight against excessive air dryness;
- dilution of the air mixture with inert gases to reduce the concentration of explosives.
Dust explosions are characteristic not only of mines, but also of buildings and granaries.
Steam cloud explosions
They are reactions of a lightning-fast state transition, generating the formation of a blast wave. Occur in the open air, in a confined space due to the ignition of a combustible vapor cloud. Typically, this occurs with a leak of liquefied gas.
For safety reasons, it is recommended that you carefully observe the following precautions:
- refusal to work with combustible gas or steam;
- rejection of ignition sources capable of causing a spark;
- avoidance of confined spaces.
It is necessary to understand soundly what an explosion is, what danger it carries. Failure to comply with safety rules and the illiterate use of certain items leads to disaster.
