Water is a universal fire extinguishing agent; in addition, it is very acceptable and is available at any production site in unlimited quantities. So, to extinguish small fires, you can use the nearest water tap. To supply large quantities of water, enterprises create an internal fire water supply system.

The use of water is especially effective when extinguishing solid flammable materials - wood, paper, rubber, fabrics, which are the most frequently burned materials in a fire. It is also good to extinguish flammable liquids that dissolve in it with water - alcohols, acetone, organic acids.

The fire extinguishing properties of water increase sharply if it enters the combustion zone in the form of sprayed jets, which reduces its consumption.

Water is successfully used to localize the source of fire when the fire cannot be quickly extinguished. In this case, water is poured over all flammable substances, materials, structures and installations located in close proximity to the source of fire.

This is exactly what is done in rooms and areas where cylinders with various compressed gases are installed. This technique is successfully used until cylinders or other objects are evacuated into safe place.

Water is very effective in extinguishing fires, but its use in radio electronics enterprises is less often limited. First of all, this is due to the fact that the electrical conductivity of water is quite high, therefore, it cannot extinguish burning electrical equipment that is under voltage.

Also, water cannot be used if there are alkali metals - sodium, potassium - in the fire zone.

It is especially dangerous if water gets into burning oil tanks and other containers with burning liquids or solids that melt when heated, since depending on the amount of water and the temperature of the liquid, it either boils violently or splashes and releases the burning liquid into the room. As a result, the burning intensity increases and the fire area expands. At the same time, the use of sprayed water jets makes it possible to successfully extinguish many flammable liquids, including various oils and kerosene.

4.3.2 Primary fire extinguishing means include:

· boxes with sand;

· felt 1x1 sq.m., asbestos sheet;

· fire extinguishers;

· tap water

Asbestos sheets and felt blankets are used to extinguish substances and materials whose combustion stops without air access. These products completely cover the source of the fire. These products are effective in case of fire that occurs in smooth surface(by floor of the room) and sunbathing area smaller size linens or blankets.

Sand is extinguished or collected small quantities spilled flammable liquids, gases or solids that cannot be extinguished with water.

4.3.3 Fire extinguishers

Currently, the industry produces various hand-held, mobile and stationary fire extinguishers.

In order to successfully fight a fire, you must clearly know the capabilities and areas of application of each fire extinguisher.

Carbon dioxide fire extinguishers OU – 2; OU - 3; OU – 5; OU – 8:

Manual fire extinguishers are steel cylinders with a socket.

To activate the fire extinguisher, you need to remove the fire extinguisher from the bracket, bring it to the fire, break the seal, pull out the pin, move the fire extinguisher bell to a horizontal position, pointing it at the fire, and press the lever.

The stream of liquefied carbon dioxide emerging from the cylinder through the socket is greatly cooled and turns into gaseous state(snow).

The fire extinguishing effect is due to a decrease in oxygen concentration in the combustion zone and cooling of the burning material. All three devices are designed to extinguish initial fires various substances and materials, as well as electrical equipment under voltage up to 1000V.

This is due to the fact that carbon dioxide does not contain water.

OU - cannot be extinguished:

· burning clothing on a person (can cause frostbite)

Use to stop burning alkali metals, as well as substances that continue to burn without access to oxygen from the environment (for example: a composition based on nitrate, nitrocellulose, pyroxylin).

Since carbon dioxide can evaporate from the cylinder, its charge should be controlled by mass and periodically refilled.

Powder manual fire extinguishers: OP – 4(g); OP-5(g); OP-8(g); (gas generator type):

Powder fire extinguishers are designed to extinguish small fires of flammable liquids and electrical installations under voltage up to 1000V.

Manual fire extinguishers consist of a steel body inside which contains a charge (powder) and a cylinder with working gas or a gas generator. Operating principle: when the shut-off and starting device is activated, the plug of the cylinder with the working gas is pierced ( carbon dioxide, nitrogen). Gas enters the lower part of the fire extinguisher body through the supply tube and creates excess pressure. The powder is forced out through a siphon tube into a hose to the barrel. By pressing the barrel trigger, you can feed the powder in portions. The powder, falling on the burning substance, isolates it from oxygen and air.

Powder manual fire extinguishers: OP – 2(z); OP-3(z); OP-4(z); OP – 8(z) (download type):

Manual fire extinguishers consist of a steel body with a charge (powder) inside under pressure. Operating principle: the working gas is pumped directly into the fire extinguisher body. When the shut-off trigger device is triggered, the powder is displaced by gas through a siphon tube into the hose to the barrel-nozzle or nozzle. The powder can be served in portions. When it hits a burning substance, it isolates it from oxygen and air.

To activate: remove the fire extinguisher from the bracket, bring it to the fire, break the seal, pull out the pin, point the hose with the nozzle at the fire, press the lever.

It should be taken into account that since powders generally have the ability to slow down the rate of combustion reaction and, to some extent, isolate the combustion site from air oxygen, their cooling effect is small. This can lead to the fact that if the thickness of the powder layer is insufficient due to the small size of the fire extinguisher charges, repeated flashes from objects that are heated during combustion are possible.

Air-foam fire extinguishers: ORP – 5; ORP – 10:

Designed to extinguish small fires of solid and liquid flammable substances and smoldering materials at an ambient temperature not lower than +5°C. It consists of a steel body, inside of which there is a charge - a foaming agent solution and a cylinder with working gas. The principle of operation is based on the displacement of a foaming agent solution overpressure working gas (air, nitrogen, carbon dioxide). When the shut-off and starting device is activated, the plug of the cylinder with the working gas is pierced. The foaming agent is forced out by gas pressure through the siphon tube into the nozzle. In the nozzle, the foaming agent is mixed with the suction air, resulting in the formation of foam. To activate: remove the fire extinguisher from the bracket, bring it to the source of fire, break the seal, pull out the pin, point the foam generator at the source of fire, hit the start button or press the lever. Do not extinguish live electrical wiring or electrical appliances.

Air-emulsion fire extinguishers with a fluorine-containing charge OVE - 5(6) - AB - 03; OVE-2(z); OVE-4(z); OVE-8(z) (fine jet)
The latest, highly efficient, environmentally friendly and safe air-emulsion fire extinguisher (with gas cylinder high pressure) is designed to extinguish fires of solid flammable substances, flammable liquids and live electrical equipment. In air-emulsion fire extinguishers, an aqueous solution of a fluorine-containing film-forming foaming agent is used as a charge, and any water spray is used as a nozzle. The emulsion is formed when drops of a sprayed fire extinguisher charge hit a burning surface, on which a thin protective film, and the resulting foamed layer of air emulsion protects this film from exposure to flame. OVE fire extinguishers can extinguish live electrical wiring and electrical appliances only with a fine spray.

Aerosol generators (aerosol fire extinguishers) - SOT – 1; SOT – 5m; SOT – 5M:

Designed to extinguish fires in confined spaces during the combustion of flammable liquids and gases (petroleum products, solvents, alcohols), solid combustible materials of electrical equipment (including those under voltage).

In a volumetric aerosol fire extinguishing system, the extinguishing agent is an aerosol of salts and oxides of alkali and alkaline earth metals. And in a calm atmosphere, the aerosol cloud persists for up to 50 minutes. Aerosols generated when SOT-1 generators operate; SOT – 5m; SOT – 5M is non-toxic and does not cause property damage. The settled particles can be easily removed with a vacuum cleaner or washed off with water.

At all sites, including educational institutions It is necessary to keep a log of primary fire extinguishing equipment .

The condition of fire extinguishers is monitored in accordance with SP 9.13139.2009. “Fire fighting equipment. Fire extinguishers. Requirements for operation."

Procedure in case of fire

In the event of a fire, the actions of workers must first of all be aimed at ensuring the safety of workers, their evacuation and rescue.

Each employee who discovers a fire or its signs (smoke, smell or smoldering various materials, increase in temperature, etc.), must:

1. Immediately report this by phone 01 (and clearly state the address of the institution, the location of the fire, and also state your position and surname).

2. Activate the fire warning system.

3. Proceed with the evacuation of people from the building to a safe place, according to the evacuation plan.

4. Notify the head of the institution or his replacement employee about the fire.

5. Organize a meeting of fire departments, take measures to extinguish the fire using the fire extinguishing equipment available in the institution.

6. Organize a check of children and workers evacuated from the building according to the available lists.

7. If necessary, call medical and other services to the fire site.

8. Inform the head of the arriving fire department about the presence of people in the building.

9. During evacuation and fire fighting necessary:

· evacuation of people should begin from the premises in which the fire occurred and adjacent premises that are at risk of spreading the fire and its signs of combustion;

· Younger children should be evacuated first;

· thoroughly check all premises to exclude the possibility of staying in danger zone people hiding under tables, in closets and other places;

· refrain from opening windows, doors, as well as breaking glass to avoid the spread of fire and smoke into adjacent rooms;

· When leaving premises or buildings, you should close windows and doors behind you.

Water is the most widely used and effective means extinguishing fires.

Table 1: Comparison of the effectiveness of fire extinguishing agents (FAs)

Fire class	Combustible materials	Water	Foam	Powder		CO 2	Freon CF 3 Br	Other refrigerants
				PSB	PF
A	Solids that form coal (paper, wood, textiles, coal, etc.	4	4	1	3	1	2	1
IN	GZh and flammable liquids (gasoline, varnishes, solvents), melting materials (hydron, paraffin)	4	4	4	4	3	4	4
WITH	Gases (propane, methane, hydrogen, acetylene, etc.)	2	1	4	3	1	3	2
D	Metals (Al, Mg, etc.)	—	—	1	1	—	—	—
E	Electrical equipment (transformers, distribution boards and etc.)	2	—	2	2	3	4	3

As follows from Table 1, water and foam are the most effective means of extinguishing class A and B fires (class B mainly with fine or ultra-sprayed water).

The basis of the fire extinguishing effect of water is its cooling ability, which is due to its high heat capacity and heat of vaporization.

With the highest heat absorption capacity, water is the most efficient natural material for extinguishing fires. Drops of water entering the combustion center undergo two stages of heat absorption: when heated to 100°C and evaporation at a constant temperature of 100°C. In the first stage, 1 liter of water spends 335 kJ of energy, in the second phase - evaporation and transformation into water vapor - 2260 kJ.

When water enters a high-temperature zone or comes into contact with a burning substance, it partially evaporates and turns into steam. During evaporation, the volume of water increases almost 1670 times, due to which the air is displaced by water vapor from the fire source, and, as a result, the combustion zone is depleted of oxygen.

Water has high thermal stability. Its vapors can decompose into hydrogen and oxygen only at temperatures above 1700°C. In this regard, extinguishing most solid materials with water is safe, since their combustion temperature does not exceed 1300 °C.

Water can dissolve some vapors, gases and absorb aerosols. Therefore, it can be used to precipitate combustion products during fires in buildings. For these purposes, finely atomized and ultra-atomized (water mist) jets are used.

Good mobility of water ensures ease of transportation through pipelines. Water is used not only to extinguish fires, but also to cool objects located near the source of fire. Thereby preventing their destruction, explosion and fire.

Mechanism for extinguishing fires with water:

• cooling the surface and reaction zone of burning substances;
• dilution (phlegmatization) of the environment in the combustion zone with steam generated during evaporation;
• isolation of the combustion zone from the air;
• deformation of the reaction layer and flame failure due to the mechanical impact of a water jet on the flame.

When extinguishing burning oil products in tanks with water, the drops supplied to the combustion source are essential. Optimal diameter water drops are 0.1mm when extinguishing gasoline; 0.3 mm - kerosene and alcohol; 0.5mm - transformer oil and petroleum products with a flash point above 60 °C.

High efficiency of extinguishing flammable substances that have a high combustion temperature and create a high flame pressure is achieved through the use of a mixture of small and large water droplets. In this case, small drops, evaporating in the flame combustion zone, reduce its temperature, and large drops, not having time to completely evaporate, reach the burning surface, cool it and, if their kinetic energy by the time they reach the burning surface is high enough, destroy the reaction layer.

Table 2: Areas of water application for different fire classes

Fire class	Subclass	Combustible substances and materials (objects)	Water sprayed by sprinklers	Finely sprayed water	Sprayed water with wetting agent
A	A1	Solid smoldering substances wetted with water (wood, etc.)	3	3	3
	A2	Solid smoldering substances that are not wetted by water (cotton, peat, etc.)	1	1	2
	A3	Solid non-smoldering substances (plastics, etc.)	2	3	3
	A4	Rubber products	2	2	3
	A5	Museums, archives, libraries, etc.	1	1	1
IN	IN 1*	Saturated and unsaturated hydrocarbons (heptane, etc.)	—	2	1
	AT 2*	Saturated and unsaturated hydrocarbons (gasoline, etc.)	—	2	1
	AT 3*	Water-soluble alcohols (C1-C3)	—	2	1
	AT 4*	Water-insoluble alcohols (C4 and higher)	—	2	1
	AT 5**	Acids - sparingly soluble in water	3	3	3
	AT 6**	Ethers and ethers (diethyl, etc.)	3	3	3
	AT 7**	Aldehydes and ketones (acetone, etc.)	3	3	3
WITH,	C1, C2, C3		—	—	—
E***	E1	EVC	1	1	1
	E2	Telephone nodes	2	2	2
	E3	Power plants	1	1	1
	E4	Transformer substations	2	2	2
	E5	Electronics	1	1	1

Note: “1” – suitable, but not recommended; “2” – fits satisfactorily; “3” – fits well; “4” – fits perfectly; “-” - not suitable, “*” - for flammable liquids and gas liquids with a flash point of up to 90 ° C; “**” - for flammable liquids and gases with a flash point of more than 90 °C; “***”—electrical equipment is live.

Water should not be used to extinguish the following materials:

• potassium, sodium, lithium, magnesium, titanium, zirconium, uranium, plutonium;
• organoaluminum compounds (reacts explosively);
• organolithium compounds, lead azide, carbides, alkali metals, hydrides of a number of metals, magnesium, zinc, calcium carbides, barium (decomposition with release of flammable gases);
• iron, phosphorus, coal;
• sodium hydrosulfite (spontaneous combustion occurs);
• sulfuric acid, thermites, titanium chloride (strong exothermic effect);
• bitumen, sodium peroxide, fats, oils, petrolatum (intensified combustion as a result of emission, splashing, boiling).

When extinguishing with water, oil products and many other organic liquids float to the surface, as a result of which the area of ​​the fire can increase significantly. For example: in case of fire of petroleum products located in the tank, it is not recommended to extinguish it with water. Oil products float above the water. Water, as a result of heating, turns into steam. Water vapor rises upward in portions, which causes burning oil products to splash out of the tank and makes it difficult for firefighters to access the fire.

Disadvantages of water include heat freezing. To lower the freezing point, special additives (antifreeze), some alcohols (glycols), and mineral salts (K 2 CO 3, MgCl 2, CaCl 2) are used. However, these salts increase the corrosivity of water, so they are practically not used. The use of glycols significantly increases the cost of the fire extinguishing agent.

Foaming agents, antifreeze and other additives also increase the corrosivity and electrical conductivity of water. As protection against corrosion, you can metal parts and pipelines apply special coatings, or add corrosion inhibitors to the water.

Expanding the scope of application of water for extinguishing electrical equipment under voltage is possible when using it in a fine and ultra-sprayed state.

The low wetting ability and low viscosity of water make it difficult to extinguish fibrous, dusty and especially smoldering materials. Materials with a large specific surface area, the pores of which contain the air necessary for combustion, are subject to smoldering. Such materials can burn when the oxygen content in the environment is greatly reduced. Penetration of fire extinguishing agents into the pores of smoldering materials is, as a rule, quite difficult.

When introducing a wetting agent (sulfonate), the water consumption for extinguishing is reduced by four times, and the extinguishing time is reduced by half.

In some cases, extinguishing with water becomes very effective if it is thickened with, for example, sodium carboxymethylcellulose or sodium alginate. Increasing the viscosity to 1-1.5 N*s/m2 allows you to reduce the extinguishing time by about 5 times. The best additives in this case are solutions of sodium alginate and sodium carboxymethylcellulose. For example, a 0.05% solution of sodium carboxymethylcellulose provides a significant reduction in water consumption for fire extinguishing. If, under certain extinguishing conditions with ordinary water, its consumption ranges from 40 to 400 l/m2, then when using “Viscous” water - from 5 to 85 l/m2. The average damage from fire (including as a result of exposure to water on materials) is reduced by 20%.

The most commonly used additives that increase the efficiency of water use are:

• water-soluble polymers to increase adhesion to burning objects (“Viscous water”);
• polyoxyethylene to increase the capacity of pipelines (“slippery water”);
• inorganic salts to increase the efficiency of extinguishing;
• antifreeze and salts to reduce the freezing point of water.

Currently one of the most promising directions in the field of anti fire protection An object for various purposes is the use of finely and ultra-sprayed water as a fire extinguishing agent. In this form, water is capable of absorbing aerosols, precipitating combustion products and extinguishing not only burning solids, but also many flammable liquids.

When water is supplied in a fine or ultra-sprayed state, the greatest fire extinguishing effect is achieved. The use of finely and ultra-sprayed water is especially important at facilities where it is required high efficiency extinguishing, there are restrictions on water supply and minimizing damage from water spills is relevant.

With the help of finely and ultra-sprayed water, the protection of many particularly socially and industrially significant objects can be ensured. These include: residential premises, hotel rooms, offices, educational institutions, dormitories, administrative buildings, banks, libraries, hospitals, computer centers, museums and exhibition galleries, sports complexes, industrial facilities, i.e. such facilities where fire extinguishing must be carried out in initial stage quickly enough and with low water consumption.

Additional benefits of using atomized water compared to a compact jet or spray stream:

• the ability to extinguish almost all substances and materials, with the exception of substances that react with water releasing thermal energy and flammable gases;
• high extinguishing efficiency due to the increased cooling effect and uniform irrigation of the fire with water;
• minimal water consumption - insignificant consumption allows you to avoid significant damage from the consequences of a spill and ensure the possibility of use subject to a water limit;
• radiant shielding thermal radiation— use for the protection of service personnel taking part in fire extinguishing, personnel of fire departments, load-bearing and enclosing structures, as well as nearby material assets;
• dilution of flammable vapors and reduction of oxygen concentration in the combustion zone as a result of intensive formation of water vapor;
• reducing the temperature in rooms during a fire;
• uniform cooling of overheated metal surfaces load-bearing structures due to the high specific surface area of ​​the droplets, it eliminates their local deformation, loss of stability and destruction;
• effective absorption and removal of toxic gases and smoke (smoke deposition);
• low electrical conductivity of finely ultra-sprayed water - makes it possible to use it as an effective fire extinguishing agent in electrical installations under voltage;
• environmental cleanliness and toxicological safety combined with the protection of people from exposure to hazardous fire factors - allows personnel to save valuables during work automatic installation fire extinguishing

Ultra-sprayed water in the combustion zone intensively evaporates. A protective layer of water vapor can isolate the combustion zone, preventing the access of oxygen. When the oxygen concentration in the combustion area drops to 16-18%, the fire self-extinguishes.

Literature used: L.M.Meshman, V.A.Bylinkin, R.Yu.Gubin, E.Yu.Romanova. Automatic water and foam fire extinguishing systems. Design. Moscow city. — 2009

Water is one of the most effective means of extinguishing fires. This is explained by a number of specific properties inherent in it, the combination of which makes it possible to successfully extinguish even the most complex fires: high specific heat (4200 J/(kg∙K)) and high specific heat vaporization (2.3 10 6 J/kg). Both factors determine the high heat-absorbing capacity of water, which, when supplied to the combustion zone, leads to a decrease in the temperature of the latter. When the temperature of the combustion source reaches less than the self-ignition temperature of the flammable substance, fire extinguishing occurs. In addition, when the temperature in the fire is ~ 1700 °C From one volume of water, ~ 1760 volumes of water vapor are formed, which, due to the dilution of the oxidizer and combustible substance in the flame, leads to a decrease in the concentration of oxygen and combustible substance. When the oxygen concentration reaches less than the MVSC and (or) a flammable substance less than the LCP, fire extinguishing occurs.

However, water as a fire extinguishing agent cannot be used where there are alkali metals (when interacting with water they ignite), calcium carbide (when interacting with water they release flammable gas acetylene), electrical installations under voltage (short circuits and electric shock to people are possible when in contact with water). You cannot use water to extinguish flammable liquids whose density is less than the density of water, for example, oil and petroleum products, since water sinks into the layer of burning liquid and does not perform its fire-extinguishing functions.

Some of the indicated negative factors of fire extinguishing with water, for example, the impossibility of extinguishing burning petroleum products, can be eliminated by using it not in the form of compact jets, but in the form of foam or spraying to droplets of micron and submicron sizes. At the same time, the efficiency of water use increases significantly, since the heat exchange area in the “fire source - water” system increases, and, consequently, the rate of heat absorption and vaporization. In addition, both foam and an aerosol cloud with an aqueous dispersed phase are retained in the combustion zone for a longer time, for example, foam covers a solid burning object up to 40 min.

Foam consisting of water, a foaming agent and air (air-mechanical foam) is obtained using foam generators, one of the design options of which is shown in Fig. 1.

Rice. 1. Generator of air-mechanical foam of average expansion rate GPS – 200.

1 – nozzles; 2 – grid cassette; 3 – generator housing; 4 – spray body; 5 – sprayer; 6 – connecting head.

A more effective fire extinguishing agent is chemical foam, in which gas bubbles formed by a thin film of water are filled with carbon dioxide, which is inert to combustion. The use of such foam is widespread mainly in hand-held fire extinguishers of the OKP-10 type, the design and principle of operation of which will be discussed below.

As stated above, even more effective way The use of water as a fire extinguishing agent is its spraying, i.e. creating an aerosol system, the dispersed phase of which is tiny droplets of water. Such fire extinguishing is volumetric and allows you to cover a larger fire area with less water compared to traditional methods.

Modern technologies Volumetric fire extinguishing with water uses a unique pneumoacoustic method of creating a water aerosol using a special nozzle that creates the so-called “protective fog” (fine water mist). Water mist effectively affects all fire extinguishing factors: quickly reduces its temperature; concentration of flammable gases and vapors, as well as oxygen. This happens due to the increase in the contact surface of water with the burning medium billions of times compared to the traditional use of water, which leads to immediate evaporation of water. At the same time, the fire extinguishing component has the penetrating ability of gas, does not harm people, property and the environment, and does not cause short circuits in electrical wiring.

MINISTRY OF EDUCATION AND SCIENCE

MOSCOW STATE CIVIL UNIVERSITY

FIRE FIGHTING MEANS AND METHODS

COURSE WORK

WATER AS A FIRE FIGHTING MEDIUM

Completed by a student

3 courses, PB group

Alekseeva Tatyana Robertovna

Moscow 2013

5. Area of ​​application of water

Bibliography

1. Fire extinguishing efficiency of water

Fire fighting is a set of actions and measures aimed at eliminating a fire. A fire can occur in the simultaneous presence of three components: a combustible substance, an oxidizer and an ignition source. The development of a fire requires the presence of not only flammable substances and an oxidizer, but also the transfer of heat from the combustion zone to the combustible material. Therefore, fire extinguishing can be achieved in the following ways:

• isolating the combustion source from the air or reducing the oxygen concentration by diluting the air with non-flammable gases to a value at which combustion cannot occur;
• cooling the combustion source to temperatures below the ignition and flash temperatures;
• slowing down chemical reactions in flames;
• mechanical flame arrest by exposing the combustion source to a strong jet of gas or water;
• creating fire suppression conditions.

The effects of all existing extinguishing agents on the combustion process depend on physical and chemical properties burning materials, combustion conditions, feed intensity and other factors. For example, water can be used to cool and isolate (or dilute) the source of combustion, foam agents can be used to isolate and cool, inert diluents can dilute the air, reducing the oxygen concentration, and freons can inhibit combustion and prevent the spread of flame by a powder cloud. For any extinguishing agent, only one fire extinguishing effect is dominant. Water has a predominantly cooling effect, foams have an insulating effect, freons and powders have an inhibitory effect.

Most extinguishing agents are not universal, i.e. acceptable for extinguishing any fires. In some cases, extinguishing agents turn out to be incompatible with burning materials (for example, the interaction of water with burning alkali metals or organometallic compounds is accompanied by an explosion).

When choosing extinguishing agents, one should proceed from the possibility of obtaining the maximum fire extinguishing effect when minimum costs. The choice of extinguishing agents must be made taking into account the class of fire. Water is the most widely used fire extinguishing agent for extinguishing fires of substances in various states of aggregation.

The high fire extinguishing efficiency of water and the large scale of its use for extinguishing fires are due to a complex of special physical and chemical properties of water and, first of all, the unusually high, in comparison with other liquids, energy intensity of evaporation and heating of water vapor. Thus, to evaporate one kilogram of water and heat the vapor to a temperature of 1000 K, it is necessary to spend about 3100 kJ/kg, while a similar process with organic liquids requires no more than 300 kJ/kg, i.e. The energy intensity of the phase transformation of water and heating of its vapor is 10 times higher than the average for any other liquid. At the same time, the thermal conductivity of water and its vapor is almost an order of magnitude higher than for other liquids.

It is well known that sprayed, highly dispersed water is most effective in extinguishing fires. To obtain a highly dispersed jet of water, as a rule, high pressure is required, but even then the range of supply of sprayed water is limited to a short distance. New principle obtaining a highly dispersed flow of water is based on a new method of obtaining atomized water - by repeated sequential dispersion of a water jet.

The main mechanism of action of water when extinguishing flames in a fire is cooling. Depending on the degree of dispersion of the water droplets and the type of fire, either the combustion zone, the burning material, or both can be cooled predominantly.

No less important factor is the dilution of a flammable gas mixture with water vapor, which leads to its phlegmatization and cessation of combustion.

In addition, sprayed water droplets absorb radiant heat, absorb the flammable component and lead to coagulation of smoke particles.

2. Advantages and disadvantages of water

Factors that determine the advantages of water as a fire extinguishing agent, in addition to its availability and low cost, are significant heat capacity, high latent heat of evaporation, mobility, chemical neutrality and lack of toxicity. Such properties of water provide effective cooling not only of burning objects, but also of objects located near the source of combustion, which helps prevent destruction, explosion and fire of the latter. Good mobility makes it easy to transport water and deliver it (in the form of continuous streams) to remote and hard-to-reach places.

The fire extinguishing ability of water is determined by the cooling effect, dilution of the flammable medium by vapors formed during evaporation and the mechanical effect on the burning substance, i.e. flame failure.

Getting into the combustion zone, onto the burning substance, water takes away a large amount of heat from the burning materials and combustion products. At the same time, it partially evaporates and turns into steam, increasing in volume 1700 times (from 1 liter of water, 1700 liters of steam are formed during evaporation), due to which the reacting substances are diluted, which in itself helps to stop combustion, as well as displace air from the zone fire source.

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

Water has low thermal conductivity, which helps create reliable thermal insulation on the surface of the burning material. This property, in combination with the previous ones, allows it to be used not only for extinguishing, but also to protect materials from ignition.

The low viscosity and non-compressibility of water allow it to be supplied through hoses over considerable distances and under high pressure.

Water can dissolve some vapors, gases and absorb aerosols. This means that combustion products from fires in buildings can be deposited with water. For these purposes, sprayed and finely sprayed jets are used.

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.

But at the same time, water has a number of disadvantages that narrow the scope of its use as a fire extinguishing agent. A large amount of water used in extinguishing can cause irreparable damage to material assets, sometimes no less than the fire itself. The main disadvantage of water as a fire extinguishing agent is that due to its high surface tension (72.8*-103 J/m 2) it does not wet solid materials and especially fibrous substances well. Other disadvantages are: freezing of water at 0°C (reduces the transportability of water at low temperatures), electrical conductivity (makes it impossible to extinguish electrical installations with water), high density(when extinguishing light burning liquids, water does not limit the access of air to the combustion zone, but, spreading, contributes to the spread of fire even more).

3. Intensity of water supply for extinguishing

Fire extinguishing agents are of paramount importance in stopping combustion. However, a fire can only be extinguished if a certain amount of fire extinguishing agent is supplied to stop it.

In practical calculations, the amount of fire extinguishing agents required to stop a fire is determined by the intensity of their supply. The supply intensity is the amount of fire extinguishing agent supplied per unit of time per unit of the corresponding geometric parameter of the fire (area, volume, perimeter or front). The intensity of the supply of fire extinguishing agents is determined experimentally and by calculations when analyzing extinguished fires:

Q O . s / 60tt P,

Where: - intensity of supply of fire extinguishing agents, l/ (m 2s), kg/ (m 2s), kg/ (m 3·cm 3/ (m 3·s), l/ (m ·s);o. с - consumption of fire extinguishing agent during fire extinguishing or conducting an experiment, l, kg, m 3;t - time spent extinguishing a fire or conducting an experiment, min;

P - the value of the calculated fire parameter: area, m 2; volume, m 3; perimeter or front, m.

The supply intensity can be determined through the actual specific consumption of the fire extinguishing agent;

Qу/60tт П,

Where Qу is the actual specific consumption of the fire extinguishing agent during the cessation of combustion, l, kg, m3.

For buildings and premises, the supply intensity is determined by the tactical consumption of fire extinguishing agents on existing fires:

Qf / P,

Where Qf is the actual consumption of the fire extinguishing agent, l/s, kg/s, m3/s (see clause 2.4).

Depending on the calculation unit of the fire parameter (m 2, m 3, m) the intensity of supply of fire extinguishing agents is divided into surface, volumetric and linear.

If in regulatory documents and reference literature there is no data on the intensity of the supply of fire extinguishing agents to protect objects (for example, during fires in buildings), it is established according to the tactical conditions of the situation and the implementation of combat operations to extinguish the fire, based on the operational-tactical characteristics of the object, or is taken reduced by 4 times compared to the required intensity of supply for fire extinguishing

h = 0.25 I tr ,

The linear intensity of the supply of fire extinguishing agents for extinguishing fires is, as a rule, not given in the tables. It depends on the fire situation and, if used when calculating fire extinguishing agents, it is found as a derivative of the surface intensity:

l = I s h T ,

Where h T - extinguishing depth, m (assumed, when extinguishing with hand guns - 5 m, fire monitors - 10 m).

The total intensity of the supply of fire extinguishing agents consists of two parts: the intensity of the fire extinguishing agent involved directly in stopping the combustion I pr. g , and loss intensity I sweat.

I pr. g +I sweat .

Average, practically expedient, values ​​of the intensity of supply of fire extinguishing agents, called optimal (required, calculated), established experimentally and by practice of extinguishing fires, are given below and in Table 1

Intensity of water supply when extinguishing fires, l/ (m 2With)

Extinguishing objectIntensity1. Buildings and structuresAdministrative buildings: I - III degree of fire resistance0.06IV degree of fire resistance0.10V degree of fire resistance0.15Basements0.10Attics0.10Hangars, garages, workshops, tram and trolleybus depots0.20Hospitals0.10Residential buildings and outbuildings: I -III degree of fire resistance0. 03IV degree of fire resistance0.10V degree of fire resistance0.15Basements0.15Attics0.15Livestock buildingsI - III degree of fire resistance0.10IV degree of fire resistance0.15V degree of fire resistance0.20Cultural and entertainment institutions (theatres, cinemas, clubs, palaces of culture): Stage0.20Auditory hall0.15Utilities premises 0.15 Mills and elevators 0.14 Industrial buildings I - II degree of fire resistance 0.35 III degree of fire resistance 0, 20 IV - V degree of fire resistance 0.25 Paint shops 0, 20 Basements 0.30 Combustible coatings large areas V industrial buildings: When extinguishing from below inside the building 0.15 When extinguishing from outside from the side of the coating 0.08 When extinguishing from outside during a developed fire 0.15 Buildings under construction 0.10 Trade enterprises and warehouses of inventory items 0. 20 Refrigerators 0.10 Power plants and substations: Cable tunnels and mezzanines (supply water mist) 0, 20Machine rooms and boiler rooms0, 20Fuel supply galleries0,10Transformers, reactors, oil switches(supply of finely sprayed water) 0.102. Vehicles Cars, trams, trolleybuses in open parking lots 0.10 Airplanes and helicopters: Interior decoration(when supplying finely atomized water) 0.08 Structures with the presence of magnesium alloys 0.25 Hull 0.15 Vessels (dry cargo and passenger): Superstructures (internal and external fires) when supplying solid and finely atomized jets 0. 20 Holds 0. 203. Solid materials Loosened paper 0.30 Wood: Pulpwood, at humidity, %40 - 500, 20 Less than 400.50 Lumber in stacks within one group at humidity, %; 6 - 140.4520 - 300.30 Over 300, 20 Round timber in stacks 0.3 Chips in piles with a moisture content of 30 - 50% 0.10 Rubber (natural or artificial), rubber and rubber products 0.30 Flax in dumps (supply of finely sprayed water) 0, 20 Flax trusts (stacks, bales) 0.25 Plastics: Thermoplastics 0.14 Thermosets 0.10 Polymer materials and products made from them 0. 20 Textolite, carbolite, plastic waste, triacetate film 0.30 Peat on milling fields with a humidity of 15 - 30% (at a specific water consumption of 110 - 140 l/m2 and extinguishing time 20 min.) 0.10 Milled peat in stacks (with a specific water consumption of 235 l/m and extinguishing time 20 min.) 0. 20 Cotton and other fibrous materials: Open warehouses 0. 20 Closed warehouses 0.30 Celluloid and products made from it 0.404 . Flammable and combustible liquids (when extinguishing with finely sprayed water) Acetone 0.40 Petroleum products in containers: With a flash point below 28 ° C 0.30 C flash point 28 - 60 ° C 0, 20 C flash point more than 60 ° C 0. 20 Flammable liquid spilled on the surface of the site, in trenches in technological trays 0, 20 Thermal insulation impregnated with petroleum products0, 20Alcohols (ethyl, methyl, propyl, butyl, etc.) in warehouses and distilleries0,40 Oil and condensate around the fountain well0, 20

Notes:

When supplying water with a wetting agent, the supply intensity according to the table is reduced by 2 times.

Cotton, other fibrous materials and peat should only be extinguished with the addition of a wetting agent.

Water consumption for fire extinguishing is determined depending on the class of functional fire danger object, its fire resistance, fire hazard category (for production premises), volume according to SP 8.13130.2009, for external fire extinguishing and SP 10.13130.2009, for internal fire extinguishing.

4. Methods of supplying water for fire extinguishing

The most reliable in solving fire extinguishing problems are automatic fire extinguishing systems. These systems are activated by fire automatics based on sensor readings. In turn, this ensures prompt extinguishing of a fire without human intervention.

Automatic fire extinguishing systems provide:

sound and light warning

issuing an alarm signal to the fire department control panel

automatic closing of fire dampers and doors

automatic activation of smoke removal systems

turning off ventilation

shutdown of electrical equipment

automatic supply of fire extinguishing agent

submission notification.

The following fire extinguishing agents are used: inert gas - freon, carbon dioxide, foam (low, medium, high expansion), fire extinguishing powders, aerosols and water.

fire extinguishing water fire extinguishing efficiency

“Water” installations are divided into sprinkler systems, designed for local fire extinguishing, and deluge systems, for extinguishing fire over a large area. Sprinkler systems are programmed to operate when the temperature rises above a set point. When extinguishing a fire, a stream of sprayed water is applied in close proximity to the source of fire. The control units for these installations are of the “dry” type - for unheated objects, and the “wet” type - for rooms in which the temperature does not fall below 0 0WITH.

Sprinkler installations are effective for protecting premises where fire is expected to develop rapidly.

Sprinklers of this type of installation are very diverse, this allows them to be used in rooms with different interiors.

A sprinkler is a valve that is activated by a heat-sensitive shut-off device. Typically, this is a glass flask containing a liquid that bursts at a given temperature. Sprinklers are installed on pipelines containing water or air under high pressure.

As soon as the room temperature rises above the set point, the glass shut-off device of the sprinkler is destroyed, due to destruction, the water/air supply valve opens, and the pressure in the pipeline drops. When the pressure drops, a sensor is triggered, which starts a pump that supplies water to the pipeline. This option provides required quantity water to the location of the fire.

There are a number of sprinklers that differ from each other by different operating temperatures.

Pre-action sprinklers significantly reduce the likelihood of false alarms. The design of the device is such that both sprinklers included in the system must be opened to supply water.

Deluge systems, unlike sprinkler systems, are triggered by a command from a fire detector. This allows you to extinguish the fire early stage development. The main difference between deluge systems is that water for extinguishing a fire is supplied to the pipeline directly when a fire occurs. These systems supply significantly large quantity water to the protected area. Typically, deluge systems are used to create water curtains and cool particularly heat-sensitive and flammable objects.

To supply water to the deluge system, a so-called deluge control unit is used. The unit is activated electrically, pneumatically or hydraulically. The signal to start the deluge fire extinguishing system is given as in an automatic way- system fire alarm, and manually.

One of the new products on the fire extinguishing market is an installation with a mist water supply system.

The smallest particles of water supplied under high pressure have high penetrating and smoke-precipitating properties. This system significantly enhances the fire extinguishing effect.

Water mist fire extinguishing systems are designed and created based on equipment low pressure. This allows for highly effective fire protection with minimal water consumption and high reliability. Similar systems are used to extinguish fires of different classes. The extinguishing agent is water, as well as water with additives, or a gas-water mixture.

Water sprayed through a fine hole increases the impact area, thus increasing the cooling effect, which is then increased due to the evaporation of the water mist. This method fire extinguishing provides excellent effect of smoke particle deposition and reflection of thermal radiation.

The fire extinguishing effectiveness of water depends on the method of supplying it to the fire.

The greatest fire extinguishing effect is achieved when water is supplied in a sprayed state, since the area of ​​simultaneous uniform cooling increases.

Solid jets are used when extinguishing external and open or developed internal fires, when it is necessary to supply a large amount of water or if water needs to be infused impact force, as well as fires, when it is not possible to get close to the source, when neighboring and burning objects, structures, and apparatus are cooled from large distances. This method of extinguishing is the simplest and most common.

Continuous jets should not be used where there may be flour, coal and other dust that can form explosive concentrations.

5. Area of ​​application of water

Water is used to extinguish fires of the following classes:

A - wood, plastics, textiles, paper, coal;

B - flammable and combustible liquids, liquefied gases, oil products (extinguishing with finely sprayed water);

C - flammable gases.

Water should not be used to extinguish substances that release heat, flammable, toxic or corrosive gases upon contact with it. These substances include some metals and metallo organic compounds, metal carbides and hydrides, hot coal and iron. The interaction of water with burning alkali metals is especially dangerous. As a result of this interaction, explosions occur. If water gets on hot coal or iron, an explosive hydrogen-oxygen mixture may form.

Table 2 lists substances that cannot be extinguished with water.

Substance Nature of interaction with water Metals: sodium, potassium, magnesium, zinc, etc. React with water to form hydrogen Aluminum organic compounds React with explosion Organolithium compounds Decompose to form flammable gases Lead azide, alkali metal carbides, metal hydrides, silanes Decompose to form flammable gases Sodium hydrogen sulfate Spontaneous combustion occurs Sodium hydrogen sulfate Interaction with water accompanied by stormy heat release Bitumen, sodium peroxide, fats, oils Combustion intensifies, emissions of burning substances occur, splashing, boiling

Water installations are ineffective for extinguishing flammable and combustible liquids with a flash point less than 90 O WITH.

Water, which has significant electrical conductivity, in the presence of impurities (especially salts) increases electrical conductivity by 100-1000 times. When using water to extinguish live electrical equipment, the electric current in a stream of water at a distance of 1.5 m from the electrical equipment is zero, and with the addition of 0.5% soda it increases to 50 mA. Therefore, when extinguishing fires with water, electrical equipment is de-energized. When using distilled water, it can even extinguish high-voltage installations.

6. Water applicability assessment method

If water gets on the surface of a burning substance, pops, flashes, and splashing of burning materials on the surface may occur. large area, additional combustion, increase in flame volume, emission of burning product from technological equipment. They can be large scale or local in nature.

The lack of quantitative criteria for assessing the nature of the interaction of a burning substance with water makes it difficult to adopt optimal technical solutions using water in automatic fire extinguishing systems. To make an approximate assessment of the applicability of water products, two laboratory methods can be used. The first method consists of visual observation of the nature of the interaction of water with the test product burning in a small vessel. The second method involves measuring the volume of the releasing gas, as well as the degree of heating when the product interacts with water.

7. Ways to increase the fire extinguishing efficiency of water

To increase the scope of use of water as a fire extinguishing agent, special additives (antifreeze) are used that lower the freezing point: mineral salts (K 2CO 3, MgCl 2, CaCl 2), some alcohols (glycols). However, salts increase the corrosivity of water, so they are practically not used. The use of glycols significantly increases the cost of extinguishing.

Depending on the source, water contains various natural salts that increase its corrosivity and electrical conductivity. Foaming agents, antifreeze salts and other additives also enhance these properties. Prevent corrosion of those in contact with water metal products(fire extinguisher housings, pipelines, etc.) can be either by applying special coatings to them, or by adding corrosion inhibitors to the water. The latter are inorganic compounds (acid phosphates, carbonates, alkali metal silicates, oxidizing agents such as sodium, potassium or sodium nitrite chromates, forming a protective layer on the surface), organic compounds (aliphatic amines and other substances capable of absorbing oxygen). The most effective of them is sodium chromate, but it is toxic. Coatings are commonly used to protect fire equipment from corrosion.

To increase the fire extinguishing efficiency of water, additives are added to it to increase wetting ability, viscosity, etc.

The effect of extinguishing the flame of capillary-porous, hydrophobic materials such as peat, cotton and woven materials is achieved by adding surfactants - wetting agents - to water.

To reduce the surface tension of water, it is recommended to use wetting agents - surfactants: wetting agent brand DB, emulsifier OP-4, auxiliary substances OP-7 and OP-10, which are the products of the addition of seven to ten molecules of ethylene oxide to mono- and dialkylphenols, the alkyl radical of which contains 8-10 carbon atoms. Some of these compounds are also used as foaming agents to produce air-mechanical foam. Adding wetting agents to water can significantly increase its fire extinguishing efficiency. When introducing a wetting agent, the water consumption for extinguishing is reduced by four times, and the extinguishing time is reduced by more than half.

One way to increase the effectiveness of fire extinguishing with water is to use finely sprayed water. The effectiveness of finely atomized water is due to the high specific surface area of ​​small particles, which increases the cooling effect due to the uniform penetrating effect of water directly on the combustion site and increasing heat removal. At the same time, the harmful effects of water on the environment are significantly reduced.

Bibliography

1.Course of lectures "Means and methods of fire extinguishing"

2.AND I. Korolchenko, D.A. Korolchenko. Fire and explosion hazard of substances and materials and means of extinguishing them. Directory: in 2 parts - 2nd ed., revised. and additional - M.: Pozhnauka, 2004. - Part 1 - 713 p., - Part 2 - 747 p.

.Terebnev V.V. Firefighting Supervisor's Handbook. Tactical capabilities of fire departments. - M.: Pozhnauka, 2004. - 248 p.

.RTP Directory (Klyus, Matveykin)

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MINISTRY OF EDUCATION AND SCIENCE

MOSCOW STATE CIVIL UNIVERSITY

FIRE FIGHTING MEANS AND METHODS

COURSE WORK

WATER AS A FIRE FIGHTING MEDIUM

Completed by a student

3 courses, PB group

Alekseeva Tatyana Robertovna

Moscow 2013

Table of contents

• 5. Area of ​​application of water
• Bibliography

1. Fire extinguishing efficiency of water

Fire fighting is a set of actions and measures aimed at eliminating a fire. A fire can occur in the simultaneous presence of three components: a combustible substance, an oxidizer and an ignition source. The development of a fire requires the presence of not only flammable substances and an oxidizer, but also the transfer of heat from the combustion zone to the combustible material. Therefore, fire extinguishing can be achieved in the following ways:

isolating the combustion source from the air or reducing the oxygen concentration by diluting the air with non-flammable gases to a value at which combustion cannot occur;

cooling the combustion source to temperatures below the ignition and flash temperatures;

slowing down the rate of chemical reactions in the flame;

mechanical flame arrest by exposing the combustion source to a strong jet of gas or water;

creating fire suppression conditions.

The results of the effects of all existing extinguishing agents on the combustion process depend on the physical and chemical properties of burning materials, combustion conditions, supply intensity and other factors. For example, water can be used to cool and isolate (or dilute) the source of combustion, foam agents can be used to isolate and cool, inert diluents can dilute the air, reducing the oxygen concentration, and freons can inhibit combustion and prevent the spread of flame by a powder cloud. For any extinguishing agent, only one fire extinguishing effect is dominant. Water has a predominantly cooling effect, foams have an insulating effect, freons and powders have an inhibitory effect.

Most extinguishing agents are not universal, i.e. acceptable for extinguishing any fires. In some cases, extinguishing agents turn out to be incompatible with burning materials (for example, the interaction of water with burning alkali metals or organometallic compounds is accompanied by an explosion).

When choosing extinguishing agents, one should proceed from the possibility of obtaining maximum fire extinguishing effect at minimal cost. The choice of extinguishing agents must be made taking into account the class of fire. Water is the most widely used fire extinguishing agent for extinguishing fires of substances in various states of aggregation.

The high fire extinguishing efficiency of water and the large scale of its use for extinguishing fires are due to a complex of special physical and chemical properties of water and, first of all, the unusually high, in comparison with other liquids, energy intensity of evaporation and heating of water vapor. Thus, to evaporate one kilogram of water and heat the vapor to a temperature of 1000 K, it is necessary to spend about 3100 kJ/kg, while a similar process with organic liquids requires no more than 300 kJ/kg, i.e. The energy intensity of the phase transformation of water and heating of its vapor is 10 times higher than the average for any other liquid. At the same time, the thermal conductivity of water and its vapor is almost an order of magnitude higher than for other liquids.

It is well known that sprayed, highly dispersed water is most effective in extinguishing fires. To obtain a highly dispersed jet of water, as a rule, high pressure is required, but even then the range of supply of sprayed water is limited to a short distance. The new principle of obtaining a highly dispersed flow of water is based on a new method of obtaining atomized water - by repeated sequential dispersion of a water jet.

The main mechanism of action of water when extinguishing flames in a fire is cooling. Depending on the degree of dispersion of the water droplets and the type of fire, either the combustion zone, the burning material, or both can be cooled predominantly.

An equally important factor is the dilution of the flammable gas mixture with water vapor, which leads to its phlegmatization and cessation of combustion.

In addition, sprayed water droplets absorb radiant heat, absorb the flammable component and lead to coagulation of smoke particles.

2. Advantages and disadvantages of water

Factors that determine the advantages of water as a fire extinguishing agent, in addition to its availability and low cost, are significant heat capacity, high latent heat of evaporation, mobility, chemical neutrality and lack of toxicity. Such properties of water provide effective cooling not only of burning objects, but also of objects located near the source of combustion, which helps prevent destruction, explosion and fire of the latter. Good mobility makes it easy to transport water and deliver it (in the form of continuous streams) to remote and hard-to-reach places.

The fire extinguishing ability of water is determined by the cooling effect, dilution of the flammable medium by vapors formed during evaporation and the mechanical effect on the burning substance, i.e. flame failure.

Getting into the combustion zone, onto the burning substance, water takes away a large amount of heat from the burning materials and combustion products. At the same time, it partially evaporates and turns into steam, increasing in volume 1700 times (from 1 liter of water, 1700 liters of steam are formed during evaporation), due to which the reacting substances are diluted, which in itself helps to stop combustion, as well as displace air from the zone fire source.

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

Water has low thermal conductivity, which helps create reliable thermal insulation on the surface of the burning material. This property, in combination with the previous ones, allows it to be used not only for extinguishing, but also to protect materials from ignition.

The low viscosity and non-compressibility of water allow it to be supplied through hoses over considerable distances and under high pressure.

Water can dissolve some vapors, gases and absorb aerosols. This means that combustion products from fires in buildings can be deposited with water. For these purposes, sprayed and finely sprayed jets are used.

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.

But at the same time, water has a number of disadvantages that narrow the scope of its use as a fire extinguishing agent. A large amount of water used in extinguishing can cause irreparable damage to material assets, sometimes no less than the fire itself. The main disadvantage of water as a fire extinguishing agent is that due to its high surface tension (72.8*-103 J/m2), it does not wet solid materials and especially fibrous substances well. Other disadvantages are: freezing of water at 0°C (reduces the transportability of water at low temperatures), electrical conductivity (makes it impossible to extinguish electrical installations with water), high density (when extinguishing light burning liquids, water does not limit the access of air to the combustion zone, but, spreading, promotes further spread of fire).

3. Intensity of water supply for extinguishing

Fire extinguishing agents are of paramount importance in stopping a fire. However, a fire can only be extinguished if a certain amount of fire extinguishing agent is supplied to stop it.

In practical calculations, the amount of fire extinguishing agents required to stop a fire is determined by the intensity of their supply. The supply intensity is the amount of fire extinguishing agent supplied per unit of time per unit of the corresponding geometric parameter of the fire (area, volume, perimeter or front). The intensity of the supply of fire extinguishing agents is determined experimentally and by calculations when analyzing extinguished fires:

I = Q o. s / 60tt P,

Where:

I - intensity of supply of fire extinguishing agents, l/ (m 2 s), kg/ (m 2 s), kg/ (m 3 s), m 3 / (m 3 s), l/ (m s );

Qo. c is the consumption of fire extinguishing agent during fire extinguishing or conducting an experiment, l, kg, m 3;

Tt - time spent extinguishing a fire or conducting an experiment, min;

P is the value of the calculated fire parameter: area, m 2 ; volume, m3 ; perimeter or front, m.

The supply intensity can be determined through the actual specific consumption of the fire extinguishing agent;

I = Qу / 60tт П,

Where Qу is the actual specific consumption of the fire extinguishing agent during the cessation of combustion, l, kg, m3.

For buildings and premises, the supply intensity is determined by the tactical consumption of fire extinguishing agents on existing fires:

I = Qf / P,

Where Qf is the actual consumption of the fire extinguishing agent, l/s, kg/s, m3/s (see clause 2.4).

Depending on the design unit of the fire parameter (m2, m3, m), the intensity of supply of fire extinguishing agents is divided into surface, volumetric and linear.

If there is no data in regulatory documents and reference literature on the intensity of the supply of fire extinguishing agents to protect objects (for example, during fires in buildings), it is established according to the tactical conditions of the situation and the implementation of combat operations to extinguish the fire, based on the operational-tactical characteristics of the object, or is accepted reduced by 4 times compared to the required intensity of supply for fire extinguishing

I z = 0.25 I tr,

The linear intensity of the supply of fire extinguishing agents for extinguishing fires is, as a rule, not given in the tables. It depends on the fire situation and, if used when calculating fire extinguishing agents, it is found as a derivative of the surface intensity:

Il = I s h t,

Where h t is the depth of extinguishing, m (assumed, when extinguishing with hand guns - 5 m, with fire monitors - 10 m).

The total intensity of the supply of fire extinguishing agents consists of two parts: the intensity of the fire extinguishing agent, which is directly involved in stopping the combustion I pr. g, and the intensity of losses I sweat.

I = I pr. g + I sweat.

Average, practically expedient, values ​​of the intensity of supply of fire extinguishing agents, called optimal (required, calculated), established experimentally and by practice of extinguishing fires, are given below and in Table 1

Intensity of water supply when extinguishing fires, l/ (m 2 s)

Tab.1

Extinguishing object	Intensity
1. Buildings and structures
Administrative buildings:
I - III degree of fire resistance
IV degree of fire resistance
V degree of fire resistance
Basements
Attic spaces
Hangars, garages, workshops, tram and trolleybus depots
Hospitals
Residential buildings and outbuildings:
I - III degree of fire resistance
IV degree of fire resistance
V degree of fire resistance
Basements
Attic spaces
Livestock buildings
I - III degree of fire resistance
IV degree of fire resistance
V degree of fire resistance
Cultural and entertainment institutions (theatres, cinemas, clubs, palaces of culture):
Auditorium
Utility rooms
Mills and elevators
Industrial buildings
I - II degree of fire resistance
III degree of fire resistance
IV - V degree of fire resistance
Paint shops
Basements
Combustible coatings for large areas in industrial buildings:
When extinguishing from below inside a building
When extinguishing from outside from the coating side
When extinguishing from outside when a fire has developed
Buildings under construction
Trading enterprises and inventory warehouses
Refrigerators
Power plants and substations:
Cable tunnels and mezzanines (mist water supply)
Machine rooms and boiler rooms
Fuel galleries
Transformers, reactors, oil circuit breakers (mist water supply)
2. Vehicles
Cars, trams, trolleybuses in open parking lots
Airplanes and helicopters:
Interior finishing (with mist water supply)
Structures containing magnesium alloys
Vessels (dry cargo and passenger):
Superstructures (internal and external fires) when supplying solid and fine spray jets
3. Hard materials
Paper loosened
Wood:
Balance, at humidity, %
Lumber in stacks within one group at humidity, %;
Round timber in stacks
Chips in piles with a moisture content of 30 - 50%
Rubber (natural or artificial), rubber and rubber products
Flax fire in dumps (supply of finely sprayed water)
Flax trusts (stacks, bales)
Plastics:
Thermoplastics
Thermosets
Polymer materials and products made from them
Textolite, carbolite, plastic waste, triacetate film
Peat on milling fields with a moisture content of 15 - 30% (with a specific water consumption of 110 - 140 l/m2 and extinguishing time of 20 minutes)
Milled peat in stacks (with a specific water consumption of 235 l/m and extinguishing time of 20 minutes)
Cotton and other fiber materials:
Open warehouses
Closed warehouses
Celluloid and products made from it
4. Flammable and combustible liquids (when extinguishing with finely sprayed water)
Petroleum products in containers:
With a flash point below 28°C
With a flash point of 28 - 60°C
With a flash point of more than 60°C
Flammable liquid spilled on the surface of the site, in the trenches of technological trays
Thermal insulation impregnated with petroleum products
Alcohols (ethyl, methyl, propyl, butyl, etc.) in warehouses and distilleries
Oil and condensate around the fountain well

Notes:

1. When supplying water with a wetting agent, the supply intensity according to the table is reduced by 2 times.

2. Cotton, other fibrous materials and peat must be extinguished only with the addition of a wetting agent.

Water consumption for fire extinguishing is determined depending on the functional fire hazard class of the object, its fire resistance, fire hazard category (for industrial premises), volume in accordance with SP 8.13130.2009, for external fire extinguishing and SP 10.13130.2009, for internal fire extinguishing.

4. Methods of supplying water for fire extinguishing

The most reliable in solving fire extinguishing problems are automatic fire extinguishing systems. These systems are activated by fire automatics based on sensor readings. In turn, this ensures prompt extinguishing of a fire without human intervention.

Automatic fire extinguishing systems provide:

24-hour temperature control and presence of smoke in the protected area;

activation of sound and light alerts

issuing an alarm signal to the fire department control panel

automatic closing of fire dampers and doors

automatic activation of smoke removal systems

turning off ventilation

shutdown of electrical equipment

automatic supply of fire extinguishing agent

submission notification.

The following fire extinguishing agents are used: inert gas - freon, carbon dioxide, foam (low, medium, high expansion), fire extinguishing powders, aerosols and water.

fire extinguishing water fire extinguishing efficiency

“Water” installations are divided into sprinkler systems, designed for local fire extinguishing, and deluge systems, for extinguishing fire over a large area. Sprinkler systems are programmed to operate when the temperature rises above a set point. When extinguishing a fire, a stream of sprayed water is applied in close proximity to the source of fire. The control units of these installations are of the “dry” type - for unheated objects, and the “wet” type - for rooms in which the temperature does not fall below 0 0 C.

Sprinkler installations are effective for protecting premises where fire is expected to develop rapidly.

Sprinklers of this type of installation are very diverse, this allows them to be used in rooms with different interiors.

A sprinkler is a valve that is activated by a heat-sensitive shut-off device. Typically, this is a glass flask containing a liquid that bursts at a given temperature. Sprinklers are installed on pipelines that contain water or air under high pressure.

As soon as the room temperature rises above the set point, the glass shut-off device of the sprinkler is destroyed, due to destruction, the water/air supply valve opens, and the pressure in the pipeline drops. When the pressure drops, a sensor is triggered, which starts a pump that supplies water to the pipeline. This option ensures the supply of the required amount of water to the location of the fire.

There are a number of sprinklers that differ from each other by different operating temperatures.

Pre-action sprinklers significantly reduce the likelihood of false alarms. The design of the device is such that both sprinklers included in the system must be opened to supply water.

Deluge systems, unlike sprinkler systems, are triggered by a command from a fire detector. This allows you to extinguish a fire at an early stage of development. The main difference between deluge systems is that water for extinguishing a fire is supplied to the pipeline directly when a fire occurs. These systems supply a significantly larger amount of water to the protected area at the time of fire. Typically, deluge systems are used to create water curtains and cool particularly heat-sensitive and flammable objects.

To supply water to the deluge system, a so-called deluge control unit is used. The unit is activated electrically, pneumatically or hydraulically. The signal to start the deluge fire extinguishing system is given both automatically - by the fire alarm system - and manually.

One of the new products on the fire extinguishing market is an installation with a mist water supply system.

The smallest particles of water supplied under high pressure have high penetrating and smoke-precipitating properties. This system significantly enhances the fire extinguishing effect.

Water mist fire extinguishing systems are designed and built using low pressure equipment. This allows for highly effective fire protection with minimal water consumption and high reliability. Similar systems are used to extinguish fires of different classes. The extinguishing agent is water, as well as water with additives, or a gas-water mixture.

Water sprayed through a fine hole increases the impact area, thus increasing the cooling effect, which is then increased due to the evaporation of the water mist. This fire extinguishing method provides an excellent effect of deposition of smoke particles and reflection of thermal radiation.

The fire extinguishing effectiveness of water depends on the method of supplying it to the fire.

The greatest fire extinguishing effect is achieved when water is supplied in a sprayed state, since the area of ​​simultaneous uniform cooling increases.

Solid jets are used when extinguishing external and open or developed internal fires, when it is necessary to supply a large amount of water or if the water needs to be given impact force, as well as fires when it is not possible to get close to the source, when cooling neighboring and burning objects from large distances, structures, devices. This method of extinguishing is the simplest and most common.

Continuous jets should not be used where there may be flour, coal and other dust that can form explosive concentrations.

5. Area of ​​application of water

Water is used to extinguish fires of the following classes:

A - wood, plastics, textiles, paper, coal;

B - flammable and combustible liquids, liquefied gases, oil products (extinguishing with finely sprayed water);

C - flammable gases.

Water should not be used to extinguish substances that release heat, flammable, toxic or corrosive gases upon contact with it. Such substances include some metals and organometallic compounds, metal carbides and hydrides, hot coal and iron. The interaction of water with burning alkali metals is especially dangerous. As a result of this interaction, explosions occur. If water gets on hot coal or iron, an explosive hydrogen-oxygen mixture may form.

Table 2 lists substances that cannot be extinguished with water.

Tab.2

Substance	Nature of interaction with water
Metals: sodium, potassium, magnesium, zinc, etc.	React with water to form hydrogen
Organoaluminum compounds	React explosively
Organolithium compounds
Lead azide, alkali metal carbides, metal hydrides, silanes	Decomposes to form flammable gases
Sodium hydrogen sulfate	Spontaneous combustion occurs
Sodium hydrogen sulfate	Interaction with water is accompanied rapid heat release
Bitumen, sodium peroxide, fats, oils	Combustion intensifies, emissions occur burning substances, splashing, effervescence

Water installations are ineffective for extinguishing flammable and combustible liquids with a flash point of less than 90 o C.

Water, which has significant electrical conductivity, in the presence of impurities (especially salts) increases electrical conductivity by 100-1000 times. When using water to extinguish live electrical equipment, the electric current in a stream of water at a distance of 1.5 m from the electrical equipment is zero, and with the addition of 0.5% soda it increases to 50 mA. Therefore, when extinguishing fires with water, electrical equipment is de-energized. When using distilled water, it can even extinguish high-voltage installations.

6. Water applicability assessment method

If water gets on the surface of a burning substance, pops, flashes, splashing of burning materials over a large area, additional fire, an increase in the volume of the flame, and the ejection of a burning product from the process equipment are possible. They can be large scale or local in nature.

The lack of quantitative criteria for assessing the nature of the interaction of a burning substance with water makes it difficult to make optimal technical solutions using water in automatic fire extinguishing installations. To make an approximate assessment of the applicability of water products, two laboratory methods can be used. The first method consists of visual observation of the nature of the interaction of water with the test product burning in a small vessel. The second method involves measuring the volume of the releasing gas, as well as the degree of heating when the product interacts with water.

7. Ways to increase the fire extinguishing efficiency of water

To increase the scope of use of water as a fire extinguishing agent, special additives (antifreeze) are used that lower the freezing point: mineral salts (K 2 CO 3, MgCl 2, CaCl 2), some alcohols (glycols). However, salts increase the corrosivity of water, so they are practically not used. The use of glycols significantly increases the cost of extinguishing.

Depending on the source, water contains various natural salts that increase its corrosivity and electrical conductivity. Foaming agents, antifreeze salts and other additives also enhance these properties. Corrosion of metal products in contact with water (fire extinguisher housings, pipelines, etc.) can be prevented either by applying special coatings to them or by adding corrosion inhibitors to water. The latter are inorganic compounds (acid phosphates, carbonates, alkali metal silicates, oxidizing agents such as sodium, potassium or sodium nitrite chromates, forming a protective layer on the surface), organic compounds (aliphatic amines and other substances capable of absorbing oxygen). The most effective of them is sodium chromate, but it is toxic. Coatings are commonly used to protect fire equipment from corrosion.

To increase the fire extinguishing efficiency of water, additives are added to it to increase wetting ability, viscosity, etc.

The effect of extinguishing the flame of capillary-porous, hydrophobic materials such as peat, cotton and woven materials is achieved by adding surfactants - wetting agents - to water.

To reduce the surface tension of water, it is recommended to use wetting agents - surfactants: wetting agent brand DB, emulsifier OP-4, auxiliary substances OP-7 and OP-10, which are the products of the addition of seven to ten molecules of ethylene oxide to mono- and dialkylphenols, the alkyl radical of which contains 8-10 carbon atoms. Some of these compounds are also used as foaming agents to produce air-mechanical foam. Adding wetting agents to water can significantly increase its fire extinguishing efficiency. When introducing a wetting agent, the water consumption for extinguishing is reduced by four times, and the extinguishing time is reduced by more than half.

One way to increase the effectiveness of fire extinguishing with water is to use finely sprayed water. The effectiveness of finely atomized water is due to the high specific surface area of ​​small particles, which increases the cooling effect due to the uniform penetrating effect of water directly on the combustion site and increasing heat removal. At the same time, the harmful effects of water on the environment are significantly reduced.

Bibliography

1. Course of lectures "Means and methods of fire extinguishing"

2. A.Ya. Korolchenko, D.A. Korolchenko. Fire and explosion hazard of substances and materials and means of extinguishing them. Directory: in 2 parts - 2nd ed., revised. and additional - M.: Pozhnauka, 2004. - Part 1 - 713 p., - Part 2 - 747 p.

3. Terebnev V.V. Firefighting Supervisor's Handbook. Tactical capabilities of fire departments. - M.: Pozhnauka, 2004. - 248 p.

4. RTP Directory (Klyus, Matveikin)

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