Explosion definition by obzh. General information about the explosion. Steam cloud explosions

release of a large amount of energy in a limited amount in a short period of time. V. leads to the formation of a highly heated gas (plasma) with a very high pressure, which, when expanded, has a mechanical effect (pressure, destruction) on the surrounding bodies. In a solid medium, it is accompanied by its destruction and crushing. V. is carried out most often due to the release chemical energy explosives.

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Explosion

rapid transformation of matter (explosive combustion), accompanied by the release of energy and the formation of compressed gases capable of doing work. A blast wave propagates in the environment. The amount released at c. Energy determines the scale (volume, area) of destruction. The value of energy concentration per unit volume determines the intensity of destruction in the explosion site. Explosion pressure, kpa scale of damage to buildings 100 total destruction of buildings 5350% destruction of buildings 28 medium damage to buildings 12 moderate damage to buildings (damage to internal partitions, frames, doors, etc.) 3 small damage to buildings (broken part of the glazing) damage to a person is taken as a boundary value in determining the category of premises and buildings, outdoor installations. At pressure in Below 5 kPa, a room, building, outdoor installation does not belong to category a or b in terms of fire and explosion hazard. During diffusion combustion of solid and liquid substances (materials) under fire conditions c. Not implemented. However, with the accumulation in a closed volume of products of thermal and thermo-oxidative degradation (hydrogen, methane, carbon monoxide, etc.), V. can occur. An example is in. Silos and bunkers at elevators, feed mills. During self-heating and subsequent spontaneous combustion of plant materials, decomposition products accumulate in burned-out cavities and ignite from vaults when vaults collapse. Designed V. They are used in military affairs, mining, construction, etc.

Public catering enterprises use and process combustible and explosive raw materials in various states of aggregation (essences, organic acids, fats, oils, flour, powdered sugar, etc.). In addition, the production is equipped with vessels and apparatus operating under excessive pressure, including refrigeration units, the refrigerant of which, as a rule, is an explosive gas or ammonia. For heating, drying, frying, cooking, baking, thermal equipment operating on a thermal manifestation is used. electric current, gas, liquid and solid fuels. Based on the properties of circulating substances, the nature of technological processes, food production is classified as explosive and fire hazardous.

Explosion called the rapid release of energy associated with a sudden change in the state of matter, accompanied by the destruction of the environment and the propagation of a shock or explosive wave in it, the transition of the initial energy into the energy of the movement of matter.

During an explosion, pressures of tens and hundreds of thousands of atmospheres develop, and the speed of movement explosive measured in kilometers per second.

Explosives- these are compounds or mixtures capable of rapid, self-propagating chemical transformation with the formation of gases and the release of a significant amount of heat. Such a transformation, having arisen at some point under the influence of an appropriate impulse (heating, mechanical shock, explosion of another explosive), spreads at high speed to the entire mass of the explosive.

The rapid formation of significant volumes of gases and their heating to high temperatures (1800 ... 3800 ° C) due to the heat of reaction explain the reason for the occurrence of high pressure at the site of the explosion.

In contrast to the combustion of conventional fuel, the explosion reaction proceeds without the participation of atmospheric oxygen and, due to the high speeds of the process, makes it possible to obtain enormous powers in a small volume. For example, 1 kg of coal requires about 11 m 3 of air, and approximately 9300 W of heat is released. An explosion of 1 kg of hexogen occupying a volume of 0.00065 m 3 occurs in a hundred-thousandth of a second and is accompanied by the release of 1580 W of heat.

In some cases, the initial energy from the very beginning is the thermal energy of the compressed gases. At some point, due to the removal or weakening of bonds, gases can expand and an explosion will occur. An explosion of cylinders with compressed gases can be attributed to this kind of explosion. Explosions of steam boilers are related to this type of explosions. However, the initial energy of compressed gases in them is only a part of the energy of the explosion; An essential role here is played by the presence of a superheated liquid, which can quickly evaporate when the pressure is reduced.

The causes and nature of the explosion may be different.

chain theory the occurrence of a gas explosion determines the conditions under which chain reactions occur. Chain reactions are chemical reactions in which active substances (free radicals) appear. Free radicals, unlike molecules, have free unsaturated valences, which leads to their easy interaction with the original molecules. When a free radical interacts with a molecule, one of the valence bonds of the latter breaks and, thus, a new free radical is formed as a result of the reaction. This radical, in turn, readily reacts with another parent molecule, re-forming a free radical. As a result, by repeating these cycles, an avalanche-like increase in the number of active explosive centers occurs.

Thermal energy proceeds from the conditions of violation of thermal equilibrium, in which the heat input due to the reaction becomes greater than the heat transfer. The heating that occurs in the system additionally affects the reaction. As a result, a progressive increase in the reaction rate occurs, leading under certain conditions to an explosion. When exposed to heat, an explosion of high power and relatively slow combustion can form.

Explosion on impact is associated with the action of local microscopic heating, which is especially strong due to the presence of very high pressure upon impact. Local heating covers a huge number of molecules and, under certain conditions, leads to an explosion.

The compression and movement of the environment (air, water, soil) arising from the explosion are transmitted to more and more distant layers. A special kind of perturbation propagates in the medium - a shock, or explosive, wave. When this wave arrives at any point in space, the density, temperature and pressure increase abruptly and the substance of the medium begins to move in the direction of wave propagation. The speed of propagation of a strong shock wave, as a rule, significantly exceeds the speed of sound. As it propagates, this speed decreases, and eventually the shock wave turns into an ordinary sound wave.

Near the source of the explosion, the speed of air movement can reach thousands of meters per second, and the kinetic energy of the moving air is equal to 50% of the total energy of the shock wave.

When a shock wave propagates not in an inert medium, but, for example, in an explosive, it can cause its rapid chemical transformation, which propagates through the substance at the speed of a wave, supports the shock wave and does not allow it to fade. This phenomenon is called detonation, and the shock wave that contributes to the rapid reaction is called the detonation wave.

As a rule, any explosion causes fires. Combustion is a complex physical and chemical process of interaction between a combustible substance and an oxidizing agent. Oxidants in the combustion process can be oxygen, chlorine, bromine and some other substances, such as nitric acid, berthollet salt and sodium peroxide. A common oxidizing agent in combustion processes is oxygen in the air. The oxidation reaction can self-accelerate under certain conditions. This process of self-acceleration of the oxidation reaction with its transition to combustion is called self-ignition. The conditions for the occurrence and course of combustion in this case are the presence of a combustible substance, atmospheric oxygen and an ignition source. A combustible substance and oxygen are reacting substances and constitute a combustible system, and an ignition source causes a combustion reaction in it.

Combustible systems can be chemically homogeneous and heterogeneous. Chemically homogeneous systems include systems in which the combustible substance and air are evenly mixed with each other, for example, mixtures of combustible gases, vapors or dusts with air.

Chemically heterogeneous systems include systems in which a combustible substance and air have interfaces, for example, solid combustible materials and liquids, jets of combustible gases and vapors entering the air. At. In the combustion of chemically inhomogeneous combustible systems, air oxygen continuously diffuses through the combustion products to the combustible substance and then reacts with it.

The heat released in the combustion zone is perceived by the combustion products, as a result of which they are heated to a high temperature, which is called the combustion temperature.

Kinetic combustion, i.e., the combustion of a chemically homogeneous combustible mixture of gases, vapors or dust with air, proceeds differently. If the combustible mixture comes at a certain speed from the burner, then it burns with a steady flame. The combustion of the same mixture that has filled a closed volume can cause a chemical explosion.

Kinetic combustion is possible only at a certain ratio of gas, vapors, dust and air. The minimum and maximum concentrations of combustible substances in the air that can ignite are called the lower and upper concentration limits of ignition (explosion).

All mixtures whose concentrations are between the flammable limits are called explosive and flammable.

Mixtures whose concentrations are below the lower and above the upper flammability limits are not capable of burning in closed volumes and are considered safe. However, mixtures whose concentration is above the upper limit of ignition, when leaving a closed volume of air, are capable of burning with a diffusion flame, that is, they behave like vapors and gases that are not mixed with air.

Flammable concentration limits are not constant and depend on a number of factors. The power of the ignition source, the admixture of inert gases and vapors, the temperature and pressure of the combustible mixture have a great influence on the change in the ignition limits.

An increase in the power of the ignition source leads to an expansion of the ignition (explosion) area with a decrease in the lower limit and an increase in the upper limit of ignition.

When non-combustible gases are introduced into the explosive mixture, a sharp decrease in the upper flammability limit and a slight change in the lower limit occur. The ignition area is reduced and at a certain concentration of non-combustible gases, the mixture ceases to ignite.

With an increase in the initial temperature of the explosive mixture, its ignition gap expands, while the lower limit decreases, and the upper one increases.

When the pressure of the combustible mixture decreases below normal, the ignition area decreases. At low pressure, the mixture becomes safe.

At the lower ignition limit of the mixture, the amount of heat generated is insignificant and therefore the pressure during the explosion does not exceed 0.30 ... 0.35 MPa. With an increase in the concentration of a combustible substance, the explosion pressure increases. It is 1.2 MPa for most mixtures.

With a further increase in the concentration of a combustible substance, the explosion pressure decreases and at the upper ignition limit becomes the same as at the lower one.

The explosive properties of mixtures of vapors with air do not differ from the properties of mixtures of combustible gases with air. The concentration of saturated vapors of a liquid is in a certain relationship with its temperature. These temperatures are called the temperature limits of ignition (explosion).

upper temperature limit called the highest temperature of the liquid at which a mixture of saturated vapors with air is formed, which is still capable of igniting, however, above this temperature, the resulting vapors mixed with air in a closed volume cannot ignite.

lower temperature limit called the lowest temperature of a liquid at which a mixture of saturated vapors with air is formed, capable of igniting when an ignition source is brought to it. At a lower liquid temperature, the mixture of vapors with air is not capable of igniting.

The lower temperature limit of ignition of liquids is otherwise called the flash point, which is taken as the basis for classifying liquids according to their degree of fire hazard. So, liquids with a flash point up to 45 ° C are called flammable, and above 45 ° C - combustible.

At food enterprises, many technological processes are accompanied by the release of fine organic dust (flour, powdered sugar, starch, etc.), which, at a certain concentration, forms an explosive dust-air mixture.

Dust can be in two states: suspended in the air (aerosol) and settled on walls, ceilings, structural parts of equipment, etc. (aerogel).

Airgel is characterized by an autoignition temperature that differs little from the autoignition temperature of a solid.

The autoignition temperature of an aerosol is always much higher than that of an airgel, and even exceeds the autoignition temperature of vapors and gases. This is explained by the fact that the concentration of a combustible substance per unit volume of an aerosol is hundreds of times less than that of an airgel; therefore, the rate of heat release can exceed the rate of heat transfer only at a significantly high temperature.

In table. the self-ignition temperatures of airgel and aerosol of some dusts are given.

As with gas mixtures, ignition and flame propagation throughout the aerosol volume occur only if its concentration is above the lower ignition limit.

As for the upper flammability limits of aerosols, they are so high that in most cases they are practically unattainable. For example, the concentration of the upper flammable limit of sugar dust is 13500 g/m 3 .

The auto-ignition temperature of combustible substances is varied. For some, it exceeds 500 ° C, for others it is within the limits of the environment, which on average can be taken as 0 ... 50 ° C.

For example, yellow phosphorus at a temperature of 15°C self-heated and ignited. Substances capable of self-ignition without heating present a great fire hazard and are called spontaneously igniting, and the process of their self-heating to the stage of combustion is defined by the term spontaneous combustion. Spontaneous substances are divided into three groups:

substances that ignite spontaneously from exposure to air (vegetable oils, animal fats, brown and black coals, iron sulfides, yellow phosphorus, etc.);

substances that ignite spontaneously from exposure to water (potassium, sodium, calcium carbide, alkali metal carbides, calcium and sodium phosphorous, quicklime, etc.);

substances that ignite spontaneously when mixed with each other (acetylene, hydrogen, methane and ethylene mixed with chlorine; potassium permanganate mixed with glycerin or ethylene glycol; turpentine in chlorine, etc.).

A great explosion and fire hazard at food enterprises is a mixture of organic dust with air.

According to the fire hazard, all dusts, depending on their properties, are divided into explosive in the aerosol state and fire hazardous in the airgel state.

The first class of explosiveness includes dust with a lower flammability (explosive) limit of up to 15 g/m 3 . This class includes dust of sulfur, rosin, powdered sugar, etc.

The second class includes explosive dust with a lower flammability (explosive) limit of 16 ... 65 g / m 3. This group includes dust of starch, flour, lignin, etc.

Dusts in the airgel state are also divided into two classes according to fire hazard: the first class is the most flammable with a self-ignition temperature of up to 250 ° C (for example, tobacco dust - 205 ° C, grain dust - 250 ° C); the second class - flammable with a self-ignition temperature above 250 ° C (for example, sawdust - 275 ° C).

Explodes within 0.0001 seconds releasing 1.470 calories of heat and approx. 700 liters of gas. Cm. Explosives.

The article reproduced the text from the Small Soviet Encyclopedia.

Explosion, the process of releasing a large amount of energy in a limited amount in a short period of time. As a result of vacuum, the substance that fills the volume in which energy is released turns into a highly heated gas with very high pressure. This gas acts with great force on the environment, causing it to move. An explosion in a solid medium is accompanied by its destruction and crushing.

The movement generated by the explosion, in which there is a sharp increase in pressure, density and temperature of the medium, is called blast wave. The blast wave front propagates through the medium at high speed, as a result of which the area covered by the movement expands rapidly. The occurrence of a blast wave is a characteristic consequence of V. in various media. If there is no medium, that is, an explosion occurs in a vacuum, the energy of V. passes into the kinetic energy of V. products flying in all directions at high speed. By means of an explosive wave (or V. products flying in a vacuum), V. produces a mechanical effect on objects located on at various distances from location B. As the distance from the explosion site, the mechanical effect of the blast wave weakens. The distances at which blast waves create the same impact force at V. of different energies increase in proportion to the cube root of the energy of V. Proportionally to the same value, the time interval for the impact of the blast wave increases.

Various types of explosions differ in the physical nature of the energy source and the way it is released. Typical examples of explosives are explosions of chemical explosives. Explosives have the ability for rapid chemical decomposition, in which the energy of intermolecular bonds is released in the form of heat. Explosives are characterized by an increase in the rate of chemical decomposition with increasing temperature. At a relatively low temperature, chemical decomposition proceeds very slowly, so that the explosive may not undergo a noticeable change in its state for a long time. In this case, between the explosive and environment thermal equilibrium is established, in which continuously released small amounts of heat are removed outside the substance through heat conduction. If conditions are created under which the released heat does not have time to be removed outside the explosive, then due to an increase in temperature, a self-accelerating process of chemical decomposition develops, which is called thermal decomposition. Due to the fact that heat is removed through the outer surface of the explosive, and its release occurs in the entire volume of the substance, thermal equilibrium can also be disturbed with an increase in the total mass of the explosive. This circumstance is taken into account when storing explosives.

Another process for the implementation of the explosion is possible, in which the chemical transformation propagates through the explosive successively from layer to layer in the form of a wave. The leading edge of such a wave moving at high speed is shock wave- a sharp (jump-like) transition of a substance from its initial state to a state with very high pressure and temperature. The explosive material, compressed by the shock wave, is in a state in which chemical decomposition proceeds very quickly. As a result, the region in which the energy is released is concentrated in a thin layer adjacent to the surface of the shock wave. The release of energy ensures that the high pressure in the shock wave is maintained at a constant level. The process of chemical transformation of an explosive, which is introduced by a shock wave and is accompanied by a rapid release of energy, is called detonation. Detonation waves propagate through the explosive at a very high speed, always exceeding the speed of sound in the original substance. For example, detonation wave velocities in solid explosives are several km/sec. A ton of solid explosive can be converted in this way into a dense gas with very high pressure in 10 -4 seconds. The pressure in the resulting gases reaches several hundred thousand atmospheres. The effect of a chemical explosive explosion can be enhanced in a specific direction by the application of specially shaped explosive charges (see below). Cumulative effect).

Explosions associated with more fundamental transformations of substances include nuclear explosions. In a nuclear explosion, the transformation atomic nuclei the initial substance into the nuclei of other elements, which is accompanied by the release of binding energy elementary particles(protons and neutrons) that make up the atomic nucleus. Nuclear V. is based on the ability of certain isotopes heavy elements uranium or plutonium to fission, in which the nuclei of the original substance decay, forming nuclei of lighter elements. In the fission of all the nuclei contained in 50 g of uranium or plutonium, the same amount of energy is released as in the detonation of 1000 tons of trinitrotoluene. This comparison shows that nuclear transformation is capable of producing B. great strength. The fission of the nucleus of an atom of uranium or plutonium can occur as a result of the capture of one neutron by the nucleus. It is essential that as a result of fission several new neutrons are produced, each of which can cause the fission of other nuclei. As a result, the number of divisions will increase very quickly (according to the law of geometric progression). If we assume that with each fission event the number of neutrons capable of causing the fission of other nuclei doubles, then in less than 90 fission events such a number of neutrons is formed that is sufficient to fission the nuclei contained in 100 kg of uranium or plutonium. The time required for the division of this amount of matter will be ~10 -6 sec. Such a self-accelerating process is called a chain reaction (cf. Nuclear chain reactions). In reality, not all neutrons produced in fission cause the fission of other nuclei. If the total amount of fissile matter is small, then most of the neutrons will escape the matter without causing fission. A fissile substance always has a small amount of free neutrons, however, a chain reaction develops only when the number of newly formed neutrons exceeds the number of neutrons that do not produce fission. Such conditions are created when the mass of the fissile material exceeds the so-called critical mass. V. occurs when the individual parts of the fissile material (the mass of each part is less than the critical one) are quickly combined into one whole with total weight exceeding the critical mass, or under strong compression, which reduces the surface area of ​​the substance and thereby reduces the number of neutrons escaping. To create such conditions, V. is usually used as a chemical explosive.

There is another type of nuclear reaction - the reaction of the fusion of light nuclei, accompanied by the release of a large amount of energy. The repulsive forces of the same electric charges (all nuclei have a positive electric charge) prevent the fusion reaction from proceeding, therefore, for an effective nuclear transformation of this type, the nuclei must have high energy. Such conditions can be created by heating substances to very high temperatures. In this regard, the fusion process, which proceeds at high temperature, is called thermonuclear reaction. During the fusion of deuterium nuclei (an isotope of hydrogen ²H), almost 3 times more energy is released than during the fission of the same mass of uranium. The temperature required for fusion is reached in a nuclear explosion of uranium or plutonium. Thus, if a fissile substance and isotopes of hydrogen are placed in the same device, a fusion reaction can be carried out, the result of which will be a V. of enormous force. In addition to a powerful blast wave, a nuclear explosion is accompanied by intense emission of light and penetrating radiation (see Fig. Damaging factors of a nuclear explosion).

In the types of explosions described above, the released energy was initially contained in the form of molecular or nuclear communications in substance. There are wind turbines in which the released energy is supplied from an external source. An example of such a voltage is a powerful electric discharge in any medium. Electric Energy in the discharge gap is released in the form of heat, turning the medium into an ionized gas with high pressure and temperature. A similar phenomenon occurs when a powerful electric current flows through a metal conductor, if the current strength is sufficient to quickly turn the metal conductor into steam. The phenomenon of V. also occurs when a substance is exposed to focused laser radiation (see. Laser). As one of the types of explosion, one can consider the process of rapid release of energy, which occurs as a result of the sudden destruction of the shell that held the high-pressure gas (for example, the explosion of a cylinder with compressed gas). B. can occur in a collision solids moving towards each other at high speed. On collision kinetic energy bodies are transformed into heat as a result of the propagation of a powerful shock wave through the substance that occurs at the moment of collision. The velocities of the relative approach of solid bodies, necessary for the substance to completely turn into vapor as a result of a collision, are measured in tens of kilometers per second, and the pressures developing in this case amount to millions of atmospheres.

Many different phenomena occur in nature, which are accompanied by V. Powerful electrical discharges in the atmosphere during a thunderstorm (lightning), sudden volcanic eruption, large meteorites are examples of different types of V. As a result of the fall Tunguska meteorite() V. occurred, equivalent in terms of the amount of energy released V. ~ 10 7 tons of trinitrotoluene. Apparently more large quantity energy was released as a result of the explosion of the Krakatoa volcano ().

Huge explosions are chromospheric flares in the sun. The energy released during such flashes reaches ~10 17 J (for comparison, we point out that at V. 10 6 tons of trinitrotoluene, an energy equal to 4.2·10 15 J would be released).

The nature of giant explosions occurring in outer space are flares new stars. During flashes, apparently within a few hours, an energy of 10 38 -10 39 J is released. Such energy is emitted by the Sun in 10-100 thousand years. Finally, even more gigantic V., going far beyond the limits of human imagination, are flashes supernovae, at which the released energy reaches ~ 10 43 J, and V. in the nuclei of a number of galaxies, the energy estimate of which leads to ~ 10 50 J.

Explosions of chemical explosives are used as one of the main means of destruction. They have great destructive power nuclear explosions. Explosion of one nuclear bomb can be equivalent in energy to V. tens of million tons of chemical explosive.

Explosions have found wide peaceful application in scientific research and in industry. V. allowed to achieve significant progress in the study of the properties of gases, liquids and solids at high pressures and temperatures (see. High pressure). The study of explosions plays an important role in the development of the physics of nonequilibrium processes, which studies the phenomena of mass, momentum and energy transfer in various media, mechanisms phase transitions substances, the kinetics of chemical reactions, etc. Under the influence of V., such states of substances can be achieved that are inaccessible with other methods of research. Powerful compression of the channel of an electric discharge by means of a chemical explosive makes it possible to obtain, within a short period of time, magnetic fields huge tension [up to 1.1 Ha/m (up to 14 million Oe), see A magnetic field. The intense emission of light during the V. of a chemical explosive in a gas can be used to excite an optical quantum generator (laser). Under the action of high pressure, which is created during the detonation of an explosive, explosive stamping, explosive welding and explosive hardening of metals are carried out.

The experimental study of explosives consists in measuring the velocities of propagation of explosive waves and the velocities of the movement of matter, measuring rapidly changing pressure, the distributions of density, intensity, and spectral composition of electromagnetic and other types of radiation emitted during explosives. These data make it possible to obtain information about the speed of various processes, accompanying V., and determine the total amount of released energy. The pressure and density of matter in a shock wave are connected by certain relationships with the velocity of the shock wave and the velocity of the matter. This circumstance makes it possible, for example, to calculate pressures and densities on the basis of velocity measurements in cases where their direct measurement is inaccessible for some reason. To measure the main parameters that characterize the state and speed of movement of the medium, various sensors are used that convert a certain type of impact into an electrical signal, which is recorded using oscilloscope or other recording device. Modern electronic equipment makes it possible to register phenomena occurring during time intervals of ~ 10 -11 sec. Measurements of the intensity and spectral composition of light radiation using special photocells and spectrographs serve as a source of information about the temperature of a substance. High-speed photography, which can be carried out at a speed of up to 10 9 frames per second, is widely used for recording the phenomena that accompany shooting.

In laboratory studies of shock waves in gases, a special device is often used - a shock tube (see Fig. Aerodynamic tube). A shock wave in such a pipe is created as a result of the rapid destruction of the membrane separating the high-pressure and low-pressure gases (this process can be regarded as the simplest type of blowing). When studying waves in shock tubes, interferometers and penumbral optical devices are effectively used, the operation of which is based on a change in the refractive index of a gas due to a change in its density.

Explosive waves propagating over long distances from their place of origin serve as a source of information about the structure of the atmosphere and the inner layers of the Earth. Waves at very large distances from the place of V. are recorded by highly sensitive equipment, which makes it possible to record pressure fluctuations in the air up to 10 -6 atmospheres (0.1 n / m²) or soil movements ~ 10 -9 m.

Literature:

• Sadovsky M.A., Mechanical action of air shock waves of an explosion according to experimental data, in the collection: Physics of the explosion, No. 1, M., 1952;
• Baum F. A., Stanyukovich K. P. and Shekhter B. I., Fizika vzryva, M., 1959;
• Andreev K. K. and Belyaev A. F., Theory of explosives, M., 1960:
• Pokrovsky G. I., Explosion, M., 1964;
• Lyakhov G. M., Fundamentals of explosion dynamics in soils and liquid media, M., 1964;
• Dokuchaev M. M., Rodionov V. N., Romashov A. N., Ejection explosion, M., 1963:
• Cole R., Underwater explosions, trans. from English, M., 1950;
• Underground nuclear explosions, trans. from English, M., 1962;
• Action of nuclear weapons, trans. from English, M., 1960;
• Gorbatsky V. G., Space explosions, M., 1967;
• Dubovik A.S., Photographic registration of fast processes, M., 1964.

K. E. Gubkin.

This article or section uses text

physical explosion - caused by a change in the physical state of matter. chemical explosion- is caused by the rapid chemical transformation of substances, in which the potential chemical energy is converted into thermal and kinetic energy of expanding explosion products. Emergency, this is an explosion that occurred as a result of a violation of production technology, errors of maintenance personnel, or errors made during the design.

Explosive "medical environment" - is a part of the room in which an explosive atmosphere can occur in small concentrations and only for a short time due to the use of medical gases, anesthetics, skin cleansers or disinfectants.

The main damaging factors in an explosion are an air shock wave, fragmentation fields, propelling effects of surrounding objects, a thermal factor (high temperature and flame), exposure to toxic products of explosion and combustion, and a psychogenic factor.

Explosive injury occurs when the impact of an explosion on people in a confined space or in an open area, as a rule, is characterized by open and closed wounds, injuries, contusion, hemorrhages, including in the internal organs of a person, ruptures of the eardrums, bone fractures, skin burns and respiratory tract, asphyxiation or poisoning, post-traumatic stress disorder.

Explosions at industrial enterprises: deformation, destruction of technological equipment, power systems and transport lines, collapse of structures and fragments of premises, leakage of toxic compounds and poisonous substances. Explosive technological lines:

Grain elevators: dust,

Mills: flour,

Chemical plants: hydrocarbons, oxidizers. In addition to oxygen, oxygen-containing compounds (perchlorate, saltpeter, gunpowder, thermite) are oxidizing agents, some chemical elements(phosphorus, bromine).

Filling stations and oil refineries: vapors and aerosols of hydrocarbons.

The distance of damage on the example of the explosion of a tanker is 5 tons. Baiker U. 1995) I. Thermal damage from the impact of a fireball: - up to 45 m. Incompatible with life, - up to 95 m. Burns of the III degree. - up to 145 m. Burns of II degree. - up to 150 m. Burns I st. - up to 240 m. Burns of the retina. II. Mechanical damage by a shock wave: - up to 55 m. Incompatible with life, - up to 95 m. Head injury, barotrauma of the lungs and gastrointestinal tract, - up to 140 m. Rupture of eardrums.

The blast shock wave can cause great loss of life and destruction of structures. The size of the affected areas depends on the power of the explosion. The extent to which secondary measures are used depends on the likelihood of a dangerous explosive atmosphere occurring. Hazardous areas are divided into different zones according to the time- and local-dependent probability of the presence of a dangerous explosive atmosphere.

Zone 0. An area in which there is a permanent, frequent or long-term dangerous explosive environment and where a dangerous concentration of dust, aerosols or vapors can be formed. Such as mills, dryers, mixers, silos, production facilities using fuel, product pipelines, supply pipes, etc.

Zone 1. The area in which, due to the concentration of combustible vapors, aerosols, swirling, deposited dust, an accidental occurrence of a dangerous explosive atmosphere can be expected. Close proximity to loading hatches; at the sites of filling or unloading equipment; in areas with fragile equipment or lines made of glass, ceramics, etc.;

Zone 2. An area where a dangerous explosive atmosphere can be expected, but very rarely and for a short time.

Dust explosion risk assessment

In the immediate vicinity of devices containing dust from which it can leak, settle and accumulate in dangerous concentrations (mills). In the case of a dust explosion with a low concentration in the medium, the head compression wave of the explosion can cause a vortex motion of the deposited dust, which gives a high concentration of combustible material. The risk of explosion of a dust mixture is much less than that of a gas, steam or mist. Zones of accidents during volumetric explosions can cover large areas. Accident on a gas pipeline in Bashkiria (June 1989) Q2 km. Dead-871, wounded 339 people. The problem of saving people after an explosion and a fire was that almost all emergency medical equipment burned out in a flame, and about improvised means in such cases, victims and rescuers are almost forgotten.

The main criteria determining the magnitude of sanitary losses are: the type of explosive device, the power of the explosion, the location of the explosion and the time of day. Depending on the number and localization of damage can be isolated, multiple and combined. According to the severity of injuries: light, moderate, severe and extremely severe. Table 4.1. the degree of damage to people depending on the magnitude of excess pressure is presented.

Upon contact with an explosive device, explosive destruction of the outer parts of the body or destruction (detachment) of limb segments occurs. The wound process in this case has a number of features: - Acute massive blood loss and shock; - Contusions of the lungs and heart; - Traumatic endotoxicosis; - The combined nature of the impact of damaging factors.

Explosion- this is a very rapid change in the chemical (physical) state of the explosive, accompanied by the release of a large amount of heat and the formation of a large amount of gases that create a shock wave that can cause destruction with its pressure.

explosives (explosives)- special groups of substances capable of explosive transformations as a result of external influences.
Distinguish explosions :

1.Physical– the released energy is the internal energy of the compressed or liquefied gas (liquefied steam). The strength of the explosion depends on the internal pressure. The resulting destruction can be caused by a shock wave from an expanding gas or fragments of a ruptured tank (Example: destruction of compressed gas tanks, steam boilers, as well as powerful electrical discharges)

2.Chemical- an explosion caused by a rapid exothermic chemical reaction proceeding with the formation of highly compressed gaseous or vaporous products. An example would be an explosion of black powder, in which a rapid chemical reaction occurs between saltpeter, coal and sulfur, accompanied by the release of a significant amount of heat. The resulting gaseous products, heated to a high temperature due to the heat of reaction, have high pressure and, expanding, produce mechanical work.

3.atomic explosions. Rapid nuclear or thermonuclear reactions (fission reactions or combinations of atomic nuclei), in which a very large amount of heat is released. Reaction products, atomic shell or hydrogen bomb and a certain amount of the medium surrounding the bomb instantly turns into gases heated to a very high temperature, having a correspondingly high pressure. The phenomenon is accompanied by colossal mechanical work.

Chemical explosions are divided into condensed and volumetric explosions.

BUT) Under condensed explosives understood chemical compounds and mixtures that are in a solid or liquid state, which, under the influence of certain external conditions, are capable of a rapid self-propagating chemical transformation with the formation of highly heated and high-pressure gases, which, by expanding, produce mechanical work. Such a chemical transformation of explosives is commonly called explosive transformation.

The excitation of the explosive transformation of explosives is called initiation. To initiate an explosive transformation of an explosive, it is required to inform it with a certain intensity of the required amount of energy (initial impulse), which can be transferred in one of the following ways:
- mechanical (impact, prick, friction);
- thermal (spark, flame, heating);
- electric (heating, spark discharge);
- chemical (reactions with intense heat release);
- explosion of another explosive charge (explosion of a detonator cap or an adjacent charge).

Condensed explosives are divided into groups :

	Characteristic. Substance examples.
	Extremely hazardous substances Unstable. Explode even in the smallest quantities. Nitrogen trichloride; some organic peroxide compounds; copper acetylenide formed when acetylene comes into contact with copper or copper alloy
	Primary explosives Less hazardous substances. Initiating connections. Possess very high sensitivity to hit and thermal effect. They are mainly used in detonator capsules to initiate detonation in explosive charges. Lead azide, mercury fulminate.
	Secondary explosives (blasting explosives) The excitation of detonation in them occurs when exposed to a strong shock wave. The latter can be created in the process of their combustion or with the help of a detonator. As a rule, explosives of this group are relatively safe to handle and can be stored for long periods of time. Dynamites, TNT, hexogen, octogen, centralite.
	Throwing explosives, gunpowder Sensitivity to shock is very small, they burn relatively slowly. Ballistic powders are a mixture of nitrocellulose, nitroglycerin and other technological additives. Ignite by flame, spark or heat. They burn quickly outdoors. They explode in a closed vessel. At the site of the explosion of black powder containing potassium nitrate, sulfur and charcoal in a ratio of 75:15:10, a residue containing carbon remains.

Explosions can also be classified according to the types of chemical reactions:

1. Decomposition reaction - a decomposition process that gives gaseous products
2. A redox reaction is a reaction in which air or oxygen reacts with a reducing agent.
3. The reaction of mixtures - an example of such a mixture is gunpowder.

B) Volumetric explosions are of two types:

• Dust cloud explosions (dust explosions) considered as dust explosions in mine galleries and in equipment or inside a building. Such explosive mixtures arise during crushing, screening, filling, and moving dusty materials. Explosive dust mixtures have a lower explosive concentration limit (NKPV), determined by the content (in grams per cubic meter) of dust in the air. Thus, for sulfur powder, the LEF is 2.3 g/m3. The concentration limits of dust are not constant and depend on humidity, degree of grinding, content of combustible substances.

The mechanism of dust explosions in mines is based on relatively weak explosions of a gas-air mixture of air and methane. Such mixtures are already considered explosive at 5% concentration of methane in the mixture. Explosions of the gas-air mixture cause turbulence in air currents sufficient to form a dust cloud. The ignition of the dust generates a shock wave that raises even more dust, and then a powerful destructive explosion can occur.

Measures applied to prevent dust explosions:

1. ventilation of premises, objects
2. surface moistening
3. dilution with inert gases (CO 2, N2) or silicate powders

Dust explosions inside buildings and equipment most often occur at elevators, where, due to the friction of grains, a large amount of fine dust is formed during their movement.

• Steam cloud explosions- processes of rapid transformation, accompanied by the appearance of a blast wave, occurring in open air as a result of the ignition of a cloud containing combustible vapor.

Such phenomena occur when a liquefied gas leaks, as a rule, in confined spaces (rooms), where the limiting concentration of combustible elements rapidly increases, at which the cloud ignites.
Measures to be taken to prevent vapor cloud explosions:

1. minimizing the use of combustible gas or steam
2. lack of ignition sources
3. location of installations in an open, well-ventilated area

The most common emergencies associated with gas explosions, arise during the operation of municipal gas equipment.

To prevent such explosions, preventive maintenance of gas equipment is carried out annually. Buildings of explosive workshops, structures, part of the panels in the walls are made easily destructible, and the roofs are easily dropped.