The main disadvantage of water as a fire extinguishing agent. Fire extinguishing agents: chemical properties, types. mechanical stripping of the flame by exposing the combustion source to a strong jet of gas or water

3.4.1. What fire extinguishing agents exist and what are their advantages and disadvantages?

1. WATER . Mainly it has a cooling effect. Additional advantage: Oxygen is displaced when large volumes of water vapor are generated. Evaporation of 1 liter of water produces 1.7m³. saturated steam. Water is ideal for cooling many flammable substances.

Benefits:

· The sea provides an unlimited supply of water; high level heat absorption; versatility; has a low viscosity, the jet can penetrate deeply into the fire and create a film on the surface of the burning liquid (light water);

Spraying to cool large areas or cool the boundaries of a fire;

● turning into steam, displaces air (volumetric quenching).

Disadvantages:

· Possible impact on the stability of the vessel;

· Extinguishing burning liquids with water can spread the fire;

· Water is not suitable for extinguishing fires in the presence of electrical equipment or in the presence of live cables near the fire;

· Water reacts with some substances, forming poisonous vapors, and interaction with calcium carbide, sodium leads to an explosion.

· Water causes some cargo to swell (spoils the cargo).

2. CARBON GAS (CO 2). On ships, carbon dioxide CO2 is used to extinguish fires in engine rooms, cargo rooms, storerooms, and is effective for extinguishing electrical and electronic equipment using stationary installations and fire extinguishers.

At a temperature of O 0 C and a pressure of 36 kg / cm 2 CO 2 passes into a liquid state. From one liter of liquid CO 2, when expanded, 500 liters of gas are obtained. Carbon dioxide on ships is stored in pressurized cylinders. When fed into the room, it passes into a gaseous state with rapid expansion, which leads to hypothermia. As a result of supercooling, gas is emitted from the installation (fire extinguisher bell) in the form of freeze-dried snow flakes (" artificial ice») With a temperature of minus 78.5 0 С. Getting into the combustion center, СО 2 passes from a solid state to a gaseous one.

Carbon dioxide is 1.5 times heavier than air and therefore gradually concentrates in the lower part of the protected area. Extinguishing with carbon dioxide takes time and the required concentration with a volumetric extinguishing method. Combustion can be stopped when it is concentrated indoors in the range of 30-45% by volume.

Benefits:

· Inertia; relatively low cost; does not damage the cargo, does not leave marks, does not conduct electricity;

Does not form poisonous or explosive gases when in contact with most substances.

Disadvantages:

· Limited stock; does not have a cooling effect in the volumetric method; creates a risk of suffocation at a concentration of 15 - 30% in the air;

· Is not very effective when applied outdoors;

· When extinguishing magnesium, it reacts with it (oxygen is released).

3. FOAM. Suppresses fire by forming an airtight layer. This layer does not allow flammable vapors to escape from the surface, and oxygen to penetrate to the combustible substance. This prevents ignition over the foam cover. As a result of heating, the foam bubbles burst, forming a water mist that turns into steam. All this together stops the combustion process.

Advantages:

· Freely and quickly covers the surface; extinguishes burning oil products, alcohols, ethers, ketones. Due to the water contained in the solution, it has a cooling effect (extinguishing class A fires);

· Is used in conjunction with fire extinguishing powders;

· Foam creates a vapor barrier that prevents vapor from escaping to the outside;

· To obtain foam fresh, outboard or soft water is used;

· Economical water consumption, does not cause overload of fire pumps;

· Foaming agents are lightweight, the systems do not require a lot of space (compact).

Disadvantages:

· Conducts electricity; can not be used to extinguish combustible metals; limited stock; does not extinguish gases.

4 ... EXTINGUISHING POWDERS . Fire-extinguishing substances in the form of powders are divided into two groups - these are general-purpose fire-extinguishing powders - for extinguishing fires of classes A, B, C, E and special-purpose fire extinguishing powders that are used to extinguish only combustible metals. Typically, sodium bicarbonate is used as a dry powder with various additives that improve fluidity, mutual miscibility with foam, water resistance and shelf life. Ammonium phosphate, potassium bicarbonate, potassium chloride, etc. are also used as dry powder.

Dignity. The dry powder quickly knocks down the flame. The powder cloud, getting into the combustion zone, inhibits the combustion reaction. In addition, burning substances are diluted with non-combustible gases emitted as a result of thermal decomposition of powder particles. The powders used are not toxic, however, it is recommended to protect the respiratory tract when extinguishing. The powders are not harmful to the ship's equipment.

Disadvantages.Limited supply, irritating respiratory tractlead to damage to the electronics. They have a low cooling effect. They do not have penetrating power.

5 ... REFRIGERANTS, (FREONS). Freons, halons, (freons) - halogenated hydrocarbons consist of carbon and one or more halogens: fluorine, chlorine, bromine and iodine. Fire extinguishing with freons is based on chemical inhibition of the combustion reaction, i.e. binding of active centers of atoms and radicals.

Evaporating easily, the vapors of these liquids fill the entire volume of the burning room. When they reach the source of the fire, they slow down the combustion reaction and cut it off, as a result of which the fire stops.

Benefits:

· Used in small quantities; shoot down fire very quickly, do not spoil cargo and equipment; in gas injection systems, they form a homogeneous gas environment; "Penetrating" gas, spreads throughout the room, suitable for extinguishing fires with electrical equipment.

Disadvantages:

● limited stock, relatively high cost. No cooling effect, reduced visibility. When used at very high temperatures (500 ° C), the formation of toxic by-products (i.e. high toxicity) is possible. Not effective for deep-seated fires (eg mattresses, wool bales, etc.). Breathing in gallons will cause dizziness and poor motor coordination. Destroy the ozone layer.

In Russia, the most widespread are freons 13В1, 12В1, freon 114-B2, as well as a mixture of ethyl bromide (73%) and freon 114-B2 (27%) for extinguishing solid and liquid combustible substances. When the vapors in the emergency room reach 215 g per 1 cm3. free volume, the chain reaction of combustion stops. Efficiently extinguish smoldering materials. Further deliveries of these types of freons are prohibited, as they destroy the ozone layer.

6. REFRIGERANT SUBSTITUTES (GALON ). After the Montreal Protocol banned the use and production of ozone-depleting halones, an intensive search for alternative bulky extinguishing agents began. Both in our country and abroad, the latest fire extinguishing systems are manufactured and installed on ships, using finely sprayed water, aerosol generators, inert gases and non-destructive ozone layer of freons. At present, gas extinguishing systems have been created using freon FM - 200 (heptofluoropropane). Approved for use in fire extinguishing systems to protect both inhabited and uninhabited premises. To stop the fire, a low concentration of freon (7.5%) is required, which does not affect the human respiratory system.

7 ... INERT GASES (IG). Inert gases are gases or mixtures of gases that do not contain enough oxygen to support combustion.

IGs are obtained from the combustion of fossil fuel in marine boilers, and separate gas generators on diesel fuel. Nitrogen generators produce IG - NITROGEN out of thin air. The fire extinguishing effect of IG is reduced to a decrease in the oxygen concentration in the combustion center. They are used to fill the free space of tanks, holds to protect against fires and explosions, as well as to extinguish fires in holds. Nitrogen (N) - widely used in inert gas systems for inerting tanks on chemical tankers and gas tankers. For effective use of the system, the oxygen content in the IG should be no more than 5% at a gas temperature of no more than 40˚С. When unloading oil products, the supply of gases to the tanks must exceed the maximum unloading speed by 25%.

8 ... FINE SPRAY WATER . Water mist is an effective and promising extinguishing agent. It is recommended for extinguishing powdered solids, fibrous materials and flammable liquids.

To obtain finely sprayed water, screw and vortex atomizers are required at a water pressure in the line of 25-30 kg / cm 2. In this case, water particles are obtained with a size of 0.1 mm to 0.5. Such finely sprayed water in a flame turns into steam, having previously removed a significant part of the heat from the fire, and the steam, diluting the oxidizer in the fire zone, contributes to the cessation of combustion.

The required dispersion of the spray depends on the nature of the burning substances. For example, for extinguishing gasoline and dusty substances, the droplet diameter should be no more than 0.1 mm, for alcohols - 0.3 mm, for flammable liquids such as transformer oil and fibrous materials - 0.5 mm.

Finely sprayed water is now more often used in stationary installations for extinguishing fires in municipalities, incinerators, separator rooms, and automatically, since it is not dangerous to humans.

9. WATER STEAM. Water vapor for extinguishing fires is supplied to the combustion zone through special pipelines from a steam power plant. Saturated steam has the best fire-extinguishing properties. Fire extinguishing concentrations of water vapor depend on the type of combustible materials and do not exceed 35% by volume. The use of steam for extinguishing fires is effective in rooms with a volume of up to 500m 3. High temperature, danger to personnel, low rates of filling the emergency room limit the use of water vapor as a fire extinguishing agent. Steam cannot be used to extinguish heated iron up to 700 0 С and burning soot, because there is an increase in combustion and the possibility of an explosion of released hydrogen.

10. FIRE-EXTINGUISHING AEROSOLS. The principle of action of fire extinguishing aerosols is based on the inhibition of redox reactions by finely dispersed products (aerosol) of salts and oxides of alkali and alkaline earth metals formed during the combustion of an aerosol-forming charge located in the generator case and capable of being in suspension for 30-50 minutes.

The gas-aerosol mixture released when the generator is triggered is toxic, has an irritating effect on the mucous membranes of the respiratory system, therefore, you can enter the room in which the generators were used no earlier than after 30 minutes. after the termination of their work in respiratory protection or after ventilation.

11. COMBINED EXTINGUISHING MEDIA .

Combined gas-powder fire extinguishing is a new promising direction in the development of automatic protection. The principle of such extinguishing is as follows: a jet consisting of a mixture of carbon dioxide and a finely dispersed powder based on ammonium phosphate is fed into the protected volume at a high speed. This suspension, falling into the zone of the gas-phase flame, extinguishes it due to the dilution of the oxidizer with gas and the absorption of the active centers of the flame by powder particles. Powder particles that have gone through the gas phase of the flame fall on the surface of the material and block the processes of evaporation and sublimation, forming a dense glassy phosphate film on the surface, i.e. the powder works in two zones, therefore such modules were called "Bison" (two zones). The Bizon fire extinguishing module is located on the bulkhead (wall) of the protected volume at a height of up to 3.5 meters.

1) Water has high heat capacity (4187 J / kg deg) under normal conditions and high heat of vaporization (2236 kJ / kg), therefore, getting into the combustion zone, on a burning substance, water takes away from burning materials and combustion products a large number of warmth. At the same time, it partially evaporates and turns into steam, increasing in volume 1700 times (from 1 liter of water during evaporation, 1700 liters of steam are formed), due to which the reactants are diluted, which in itself contributes to the cessation of combustion, as well as the displacement of air from the zone the source of the fire.

2) Water has high thermal stability ... Its vapors only at temperatures above 1700 0 C can decompose into oxygen and hydrogen, thereby complicating the situation in the combustion zone. Most of the combustible materials burn at temperatures not exceeding 1300-1350 0 С and extinguishing them with water is not dangerous.

3) Water has low thermal conductivity , which contributes to the creation of reliable thermal insulation on the surface of the burning material. This property, in combination with the previous ones, makes it possible to use it not only for extinguishing, but also for protecting materials from ignition.

4) Low viscosity and incompressibility of water allow feeding it along the sleeves over considerable distances under high pressure.

5) Water capable of dissolving some vapors, gases and absorbing aerosols ... This means that water can precipitate combustion products on fires in buildings. For these purposes, sprayed and atomized jets are used.

6) Some flammable liquids (liquid alcohols, aldehydes, organic acids, etc.) are soluble in water, therefore, when mixed with water, they form non-flammable or less flammable solutions.

7) Water with the absolute majority of flammable substances does not enter into a chemical reaction .

Negative properties of water as a fire extinguishing agent:

1) The main disadvantage of water as a fire extinguishing agent is that due to high surface tension (72.8 · 10 -3 J / m 2) she poorly wetting solid materials and especially fibrous substances ... To eliminate this disadvantage, surfactants (surfactants), or, as they are called, wetting agents, are added to water. In practice, surfactant solutions are used, the surface tension of which is 2 times less than that of water. The use of solutions of wetting agents allows to reduce the consumption of water for extinguishing a fire by 35-50%, to reduce the extinguishing time by 20-30%, which provides extinguishing with the same volume of extinguishing agent over a larger area. For example, the recommended concentration of wetting agent in aqueous solutions for extinguishing fires:

Ø Foam concentrate PO - 1.5%;

Ø Foam concentrate PO-1D - 5%.

2) Water has relatively high density (at 4 ° C - 1 g / cm 3, at 100 ° C - 0.958 g / cm 3), which limits and sometimes excludes its use for extinguishing petroleum products with a lower density and insoluble in water.

3) The low viscosity of water contributes to the fact that a significant part of it escapes from the fire without significantly affecting the process of stopping combustion. If the viscosity of water is increased to 2.5 · 10 -3 m / s, then the extinguishing time will significantly decrease and the coefficient of its use will increase by more than 1.8 times. For these purposes, additives from organic compounds are used, for example, CMC (carboxymethyl cellulose).

4) Metallic magnesium, zinc, aluminum, titanium and its alloys, thermite and electron during combustion create a temperature in the combustion zone that exceeds the thermal resistance of water, i.e. more than 1700 0 С. Their extinguishing with water jets is unacceptable.

5) Water electrically conductive , therefore, it can not be used to extinguish electrical installations under voltage.

6) Water reacts with certain substances and materials (peroxides, carbides, alkali and alkaline earth metals, etc.) which therefore cannot be extinguished with water.

44. Fire extinguishing properties of water. Using water to extinguish a fire

Water is one of the most readily available, cheap and widespread extinguishing media, suitable for fighting both small and large fires. The fire-extinguishing properties of water lie in the fact that it has a high heat capacity, is able to take away a significant amount of heat from burning substances, reducing those

the temperature of the source of combustion to the point at which combustion becomes impossible. Water cannot be used:

· To extinguish substances that react with it, for example, the metals potassium and sodium. The evolved hydrogen, when mixed with air, forms an explosive mixture.

· When extinguishing electrical installations under voltage, as well as when extinguishing calcium carbide due to the possibility of an explosion of acetylene released during this.

For fire extinguishing, water is used in the form of compact jets, in an atomized state, in a finely dispersed state, as well as in the form of air-mechanical foam. It is impossible to use compact jets when extinguishing burning flammable liquids, since this is the spreading of liquid that floats to the surface of the water, which contributes to an increase in the combustion zone.

If water is used in a sprayed state, in the form of fine particles, when most of the sprayed water droplets have a size of less than 0.1 mm, then the surface of contact of water with burning substances increases, which contributes to a more intensive removal of heat by water from the combustion site and the formation of steam. promoting extinguishing. The spray water jet during indoor fires can be used to reduce temperature and smoke deposition. Water in the atomized state can be used to extinguish burning oil products with a flash point above 120 ° С. AAAAAAAAAAAAAAAAAAAAAAAAAAA

The addition of 0.2-2.0% (by weight) of foaming agents to water helps to lower the surface tension, as a result of which its fire-extinguishing properties are improved, water consumption is reduced by 2-2.5 times, and the extinguishing time is reduced.

45. Fire hazard properties of materials and substances. Primary extinguishing media

The main indicators of fire hazard that determine the critical conditions for the onset and development of the combustion process are the autoignition temperature and the concentration limits of ignition.

Autoignition temperature characterizes the minimum temperature of a substance or material at which a sharp increase in the rate of exothermic reactions occurs, resulting in the appearance of flame combustion.

The minimum concentration of flammable gases and vapors in the air at which they are able to ignite and spread a flame is called the lower flammable concentration limit; the maximum concentration of flammable gases and vapors, at which the spread of the flame is still possible, is called the upper concentration limit of ignition. The area of \u200b\u200bcompositions and mixtures of flammable gases and vapors with air lying between the lower and upper ignition limits is called the ignition area.

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 the greatest influence on the ignition limits.

The change in the ignition limits with increasing temperature can be estimated according to the following rule: with an increase in temperature for every 100 °, the values \u200b\u200bof the lower ignition limits decrease by 8-10%, and the upper ignition limits increase by 12-15%.

The concentration of saturated vapors of liquids is in a certain relationship with its temperature.

Using this property, the concentration limits of ignition of saturated vapors can be expressed in terms of the temperature of the liquid at which they are formed.

Dusts of many solid combustible substances suspended in air also have the ability to form high-speed flammable (explosive) mixtures with air. The minimum concentration of dust in the air at which it ignites is called the lower ignition limit of dust. Since it is practically impossible to achieve very high concentrations of dust in suspension, the term “upper flammable limit” does not apply to dusts.

The fire hazard indicators characterizing the critical conditions for the formation of sufficient for combustion of gaseous combustible products of evaporation or decomposition of condensed substances and materials include flash and ignition temperatures, as well as temperature limits of ignition.

Flash point is the lowest (under special test conditions) temperature of a combustible substance at which vapors and gases are formed above the surface that can flash in the air from an ignition source, but the rate of their formation is still insufficient for subsequent combustion. Using this characteristic, all flammable liquids can be divided into two classes in terms of fire hazard:

1) liquids with a flash point of up to 61 ° C (gasoline, ethyl alcohol, acetone, sulfuric ether, nitroenamels, etc.), they are called flammable liquids (flammable liquids);

2) liquids with a flash point above 61 ° C (oil, fuel oil, formalin, etc.), they are called flammable liquids (FL).

Ignition temperature - the temperature of a combustible substance at which it emits combustible vapors and gases at such a rate that after they are ignited from the ignition source, a stable combustion occurs. Temperature limits ignition - temperatures at which saturated vapors of a substance form in a given oxidizing environment concentrations equal to the lower and upper concentration limits of ignition of liquids, respectively.

The fire hazard of substances is characterized by linear (expressed in cm / s) and mass (g / s) rates of combustion (flame propagation) and burnout (g / m2-s or cm / s), as well as the limiting oxygen content at which combustion is still possible. For conventional combustible substances (hydrocarbons and their derivatives), this limiting oxygen content is 12-14%, for substances with a high value of the upper flammable limit (hydrogen, carbon disulfide, ethylene oxide, etc.), the limiting oxygen content is 5% and lower.

In addition to the listed parameters, for assessing fire hazard, it is important to know the degree of flammability (combustibility) of substances. Depending on this characteristic, substances and materials are divided into:

Combustible (combustible),

Hardly combustible (hardly combustible)

· Non-combustible (non-combustible).

Fuels include those substances and materials that, when ignited by an extraneous source, continue to burn even after it has been removed. Hard-combustible substances are those that are not able to spread the flame and burn only at the place of the impulse; non-combustible are substances and materials that are not flammable even when exposed to sufficiently powerful impulses.

46. \u200b\u200bAutomatic fire extinguishing installations. Causes of industrial fires

Applied in premises with high fire hazard.

1) spilinker: the outlet of the sprinkler head is closed with plates, cat. when exposed to temperature, they melt and water from the system under pressure comes out of the head hole and irrigates the structures of the room or equipment in the area of \u200b\u200bthe sprinkler head. One head irrigates an area of \u200b\u200b10-12 m.

Along with this, water has properties that limit its scope. So, when extinguishing water, oil products and many other flammable liquids float up and continue to burn on the surface, so water may be ineffective in extinguishing them. The fire extinguishing effect when extinguishing with water in such cases can be increased by supplying it in a sprayed state.

Fire extinguishing with water is carried out with water fire extinguishing installations, fire trucks and water barrels (manual and fire monitors). To supply water to these installations, they use water pipes arranged at industrial enterprises and in settlements.

In case of fire, water is used for external and internal fire extinguishing. Water consumption for external fire extinguishing is taken in accordance with building codes and regulations. Water consumption for fire extinguishing depends on the category of fire hazard of the enterprise, the degree of fire resistance building structures buildings, the volume of the industrial premises.

One of the main conditions that external water pipes must meet is to ensure constant pressure in a water supply network supported by permanent pumps, a water tower or a pneumatic unit. This pressure is often determined from the operating conditions of internal fire hydrants.

In order to ensure extinguishing a fire at the initial stage of its occurrence, in most industrial and public buildings, internal fire hydrants are arranged on the internal water supply network.

According to the method of creating water pressure, fire water pipelines are divided into high and low pressure water pipelines. High pressure fire water pipelines are arranged in such a way that the pressure in the water supply system is always sufficient to directly supply water from hydrants or stationary fire monitors to the fire site. From low-pressure water pipelines, mobile fire-fighting motor pumps or motor pumps take water through fire hydrants and supply it under the required pressure to the fire site.

The fire water supply system is used in various combinations: the choice of one or another system depends on the nature of the production, the territory it occupies, etc.

Water-based fire extinguishing installations include sprinkler and deluge installations. They are a branched, water-filled pipe system equipped with special heads. In the event of a fire, the system reacts (differently, depending on the type) and irrigates the structures of the room and equipment in response to the action of the heads.

Foam

Foams are used to extinguish solid and liquid substances that do not interact with water. The fire-extinguishing properties of foam are determined by its multiplicity - the ratio of the volume of the foam to the volume of its liquid phase, stability, dispersion and viscosity. On these properties of the foam in addition to its physical and chemical properties the nature of the combustible substance, the conditions of the fire and the supply of foam have an influence.

Depending on the method and conditions of obtaining fire extinguishing foams divided into chemical and air-mechanical. Chemical foam is formed by the interaction of solutions of acids and alkalis in the presence of a foaming agent and is a concentrated emulsion of carbon dioxide in an aqueous solution of mineral salts containing a foaming agent.

The use of chemical foam is decreasing due to the high cost and complexity of organizing fire extinguishing.

Foam generating equipment includes air-foam barrels for obtaining low-expansion foam, foam generators and foam sprinklers for obtaining medium-expansion foam.

Gases

When extinguishing fires with inert gaseous diluents, carbon dioxide, nitrogen, flue or exhaust gases, steam, as well as argon and other gases are used. The fire-extinguishing effect of these compounds is to dilute the air and reduce the oxygen content in it to a concentration at which combustion stops. The fire-extinguishing effect when diluted with these gases is due to heat loss due to heating of the diluents and a decrease in the heat effect of the reaction. A special place among fire extinguishing compositions is occupied by carbon dioxide (carbon dioxide), which is used to extinguish flammable liquids warehouses, battery stations,

drying ovens, stands for testing electric motors, etc.

It should be remembered, however, that carbon dioxide cannot be used to extinguish substances containing oxygen, alkaline and alkaline earth metals, or smoldering materials. To extinguish these substances, nitrogen or argon is used, and the latter is used in cases where there is a danger of the formation of metal nitrides with explosive properties and sensitivity to impact.

Recently, a new method of supplying gases in a liquefied state to the protected volume has been developed, which has significant advantages over the method based on the supply of compressed gases.

With the new method of supply, there is practically no need to limit the size of objects allowed for protection, since the liquid occupies about 500 times less volume than an equal amount of gas by weight, and does not require large efforts to supply it. In addition, during the evaporation of liquefied gas, a significant cooling effect is achieved and the limitation associated with the possible destruction of weakened openings disappears, since when liquefied gases are supplied, a soft filling mode is created without a dangerous increase in pressure.

Inhibitors

All of the extinguishing agents described above have a passive effect on the flame. More promising are fire extinguishing agents that effectively inhibit chemical reactions in a flame, i.e. have an inhibitory effect on them. The greatest application in fire extinguishing has found fire extinguishing compositions - inhibitors based on saturated hydrocarbons, in which one or more hydrogen atoms are replaced by halogen atoms (fluorine, chlorine, bromine).

Halocarbons are poorly soluble in water, but mix well with many organic matter... The fire extinguishing properties of halogenated hydrocarbons increase with an increase in the sea mass of the halogen contained in them.

Halocarbon compounds are convenient for fire extinguishing physical properties... Thus, high values \u200b\u200bof the density of liquid and vapors determine the possibility of creating a fire-extinguishing jet and the penetration of drops into the flame, as well as the retention of fire-extinguishing vapors near the combustion center. Low freezing temperatures allow these formulations to be used at subzero temperatures.

In recent years, powder compositions based on inorganic alkali metal salts have been used as fire extinguishing agents. They are distinguished by their high fire extinguishing efficiency and versatility, i.e. the ability to extinguish any materials, including those not extinguished by all other means.

Powder compositions are, in particular, the only means of extinguishing fires of alkali metals, organoaluminium and other organometallic compounds (they are manufactured by the industry on the basis of sodium and potassium carbonates and bicarbonates, phosphorus-ammonium salts, powder based on griffin for extinguishing metals, etc.) ...

The very first means of fighting fire in history was water. It still remains the most effective means of fire extinguishing. Water fire extinguishing is considered one of the safest for people, which is important, which is why it is used to extinguish fires in movie and concert halls, sports complexes, shopping centers, office buildings, in general, wherever a large crowd of people is constantly present.

Main advantages of water extinguishing

The most important advantage of water is its availability. Even if there is no internal water supply connected to the main line, there are always alternative water reservoirs available. These include rivers, lakes, reservoirs and other reservoirs of both natural and artificial origin.

Water is a fairly effective agent that can quickly extinguish paper, wood, coal, fabrics, rubber or flammable liquids that have the properties of dissolving in water: lower alcohol, acetone, organic acid, and others. It is best to extinguish clothes with a water solution.

The highest quality fire extinguishing occurs with the help of finely atomized droplets, the diameter of which does not exceed 0.8 mm. At the same time, the irrigated surface is significantly increased, the consumption of water is reduced, the cooling effect is increased, which contributes to its saving. Water possesses cooling and wetting properties, and therefore it is used not only to extinguish the source of fire, but also to prevent the spread of fire over large areas.

If extinguishing the flame with primary fire extinguishing means did not bring the desired result, then all material values \u200b\u200blocated in the room are poured abundantly with water, preventing their ignition, if there is no real possibility to take them out of there.

Negative points of water fire extinguishing

Despite the many advantages, water extinguishing not without flaws. First of all, water is an excellent conductor of electrical energy, therefore, in order to avoid a short circuit, which can lead to an increase in fire, it is strictly forbidden to use water to extinguish electrical equipment operating on high voltage.

Do not use water as a fire extinguishing agent to eliminate the ignition of substances that, when in contact with it, enter into a violent reaction. Aqueous solutions lose their effectiveness when interacting with burning hydrocarbons, as well as other substances that cannot mix with it, if their density does not reach unity.

Under certain circumstances, water not only does not lead to the elimination of the fire source, but also helps the flame to ignite with renewed vigor. This applies to fuels and lubricants, which do not mix with water, but rise to the surface and continue to burn there with a constantly increasing power, occupying ever large territories.

There is enough dangerous situation when water gets into oil-type baths engulfed in a flame, as well as other tanks in which there are burning high-boiling liquids or solids melting when heated. There are frequent cases of people getting terrible burns of open parts of the body when extinguishing oil in a bath with water.

It is also worth noting negative influence aqueous solution for electrical appliances, electrical engineering, paper documentation, objects of history and art. It is not recommended to use water to extinguish fires in libraries, museums, art galleries and exhibitions, archive rooms, server rooms. This can cause irreparable damage, maybe even more significant than fire damage.

Types of water fire extinguishing

Now there are such types of water fire extinguishing:

1. sprinkler systems;
2. sprinkler installations;
3. deluge systems;
4. modular fine spray units.

Sprinkler and deluge systems are a combination of the following elements:

1. pipelines (required to supply water to the combustion site);
2. pumping stations (stabilize the indicator of water pressure in pipelines);
3. sprinklers (contribute to the irrigation of places of fire).

But increasingly popular are modular-type fine-spray fire extinguishing systems. Modular installations are used where the protected object has existed for a long time and it is not possible to determine the exact amount of water for sprinkler and deluge systems, as well as to lay other expensive communication networks.

Sprinkler fire extinguishing

As a rule, these are the most elementary and reliable systems operating in automatic mode, which turn on independently at the time of increase temperature regime indoors to the critical point.

The sprinkler system includes pipes in which water is constantly kept under a certain pressure. The system ends with sprinklers (sprinklers) that are triggered after the thermal lock breaks and spray liquid onto the fire site. Moreover, sprinklers do not work all at once, but only those that are located in a place with a high temperature. The rest of the sprinklers remain unused.

The main substance in a sprinkler system is water, which comes from an ordinary plumbing system. The water pressure must be at a certain level, which is maintained by the shut-off valves. If a breakdown occurs in the pipeline system or it is completely turned off, then the water pressure in the system will be such that the device can initially work.

The advantages of such a system are as follows:

1. automatic control;
2. no need for electricity;
3. no need for complex circuits feedback;
4. long service life;
5. being in constant working capacity.

The disadvantages include the following:

1. inertia;
2. direct dependence on water supply networks;
3. do not extinguish electrical wiring;
4. works only when the temperature in the room rises.

Deluge firefighting

The main difference between drenchers and sprinklers is the lack of a thermal lock in the former, and, as a result, differences in the method of operation. Such a system is not activated when reaching high temperature at the facility, and when receiving an alarm from the central console or from fire alarms. This helps to reduce the response time of the system to a minimum, which significantly increases its efficiency.

Deluge systems can be installed at any facility. At the same time, water can be pumped into the pipelines, so the temperature in the rooms must be positive so that the water in them does not freeze and the pipes do not burst. Air can be pumped into the system, then there is no need for heated rooms.

Design of such systems

Before installing a water fire extinguishing system at an object, it is necessary to develop an appropriate project, in which the following data must appear without fail:

1. specific sources of water supply;
2. water feeders;
3. pipelines;
4. sprinklers.

1. check the compatibility of materials used at the facility with an aqueous solution;
2. define optimal view equipment;
3. determine the intensity of irrigation;
4. calculate the duration of the fire extinguishing process;
5. draw a diagram of the installation of sprinklers.

Only properly designed and professionally installed system water fire extinguishing will be able to fulfill its task - to quickly and effectively cope with a fire, preserving property and not causing harm to human health.