Calculate the foam ratio. Foam generation. Sleeve capacity

Air-mechanical foam obtained from modern foam concentrates is an effective fire extinguishing agent. The foam layer formed on the surface of the burning substance at the same time provides its isolation from the entry of new portions of oxygen, which acts as an oxidizing agent, and produces a cooling effect due to the high heat capacity of the water included in the .

The foaming process takes place on special foam-generating devices, when a working solution of a foaming agent obtained from foam concentrates with various volume fractions of application is supplied to them under pressure, when mixed with air.

Foams used for fire extinguishing purposes must have high structural and mechanical resistance to the adverse effects on them of various external factors present in the fire zone.

Foams of various expansion allow solving the problems of fire extinguishing objects of various origins by choosing the most optimal fire extinguishing agent.

Zavod Spetskhimprodukt LLC produces a wide range of products, various modifications of which make it possible to completely cover all the emerging needs in the elimination of fires of classes A and B.

General definitions

for extinguishing fires- a concentrated aqueous solution of a foam stabilizer (surfactant), which, when mixed with water, forms a working solution of a foaming agent or wetting agent.

Film-forming blowing agent- a foaming agent, the fire-extinguishing ability and resistance to re-ignition of which is determined by the formation of an aqueous film on the surface of a hydrocarbon combustible liquid.

Batch of blowing agent- any quantity of foam concentrate manufactured at the same time, homogeneous in terms of quality, accompanied by one quality document.

Foam- a dispersed system consisting of cells - air (gas) bubbles separated by films of a liquid containing a foaming agent.

Fire extinguishing air-mechanical foam- foam obtained with the help of special equipment due to ejection or forced supply of air or other gas, designed to extinguish fires.

Volume fractions of application, foam concentrate solution

The concentration of the working solution of the foaming agent - the content of the foaming agent in the working solution to obtain a foam or wetting agent solution, expressed as a percentage.

Method for obtaining foam of various concentrations:

1. To obtain foam concentrate 6%:

• To 5 parts of water add 1 part of foam concentrate 1%
• To 1 part of water add 1 part of foam concentrate 3%

2. To obtain foam concentrate 3%:

• To 2 parts of water add 1 part of 1% foam concentrate.

Example: From 1 ton of software (6%), 16.6 tons of working solution can be obtained. The same amount of working solution can be obtained from 0.17 tons of software (1%)

Advantages when using a foam concentrate with high concentrations of surfactants (volume fraction of application 1% and below):

1. Space is saved for and transport costs are reduced during its transportation

2. The stock of the transportable volume of fire extinguishing agent is increased when delivered to the fire site in the standard foam tank of a fire truck (if appropriate dosing systems are available)

3. Provides the possibility of prompt preparation of 6% and 3% foam concentrate directly on site in the absence of appropriate dosing systems (foam mixing)

Foam solution

The working solution of a foaming agent (wetting agent) is an aqueous solution with a regulated working volumetric concentration of a foaming agent (wetting agent). The working concentration of the foaming agent is from 0.5% to 6%, the wetting agent - from 0.1% to 3%.

The intensity of the supply of the working solution is the amount of an aqueous solution of the foaming agent supplied per unit time per unit surface of the combustible liquid.

The technique for obtaining a working solution of a foaming agent from a foam concentrate with various volume fractions of application consists in strictly maintaining the percentage ratio of water and the corresponding foam concentrate during their mixing.

Foam generators

Foam fire extinguishing installation - a fire extinguishing installation in which air-mechanical foam obtained from an aqueous solution of a foaming agent is used as a fire extinguishing agent

Foam generators for extinguishing from above - special devices for obtaining fire-extinguishing air-mechanical foam from a working solution of a foam concentrate by ejection or forced air supply

Subsurface fire extinguishing system in a tank - a set of devices, equipment and a fluorine-containing film-forming foam concentrate designed for subsurface fire extinguishing of oil and oil products in a reservoir.

High-pressure foam generator - a device for obtaining low-expansion air-mechanical foam from an aqueous solution of 1%, 3% or 6% and feeding it into a layer of oil or oil products under back pressure created by a liquid column in under-layer fire extinguishing installations of tanks.

Since the foaming agent solution can be obtained from foam concentrates with various volume fractions of application, it is initially necessary to be guided by the technical features of the individual dosing system, which is structurally designed for a specific concentration of the foaming agent. This circumstance must be taken into account when making an application for the purchase of a foaming agent. It should also be taken into account that the richer the foam concentrate used, the lower the probability of obtaining an optimal foam concentrate solution, since it is not always possible in practice to ensure uniform mixing of water and a highly concentrated foam concentrate during the dosing process. The working solution of the foaming agent obtained in this way will subsequently make it possible to obtain a fire-extinguishing foam, but, at a minimum, there will be an overexpenditure of the expensive foam concentrate.

Foam ratio- a dimensionless value equal to the ratio of the volumes of foam and the solution contained in the foam.

• Low expansion foam (up to 20)
• Medium expansion foam (from 21 to 200)
• High expansion foam (over 200)

Foam ratio

The ratio of the foaming agent (obtained air-mechanical foam) equally depends on both the physical and chemical properties of the initial foam concentrate for general or targeted purposes, and on the technical features of foam generators that have specific design limitations. At present, there is a tendency in the world to use only low or only high expansion foam in practice. This is due to the widespread use of fluorine-containing foam concentrates, which, due to the effect of the formation of a self-spreading water film (local fire extinguishing on the surface of a combustible liquid), make it possible to limit oneself to low expansion foam to quickly achieve fire extinguishing goals. In cases of forced volumetric fire extinguishing (aircraft hangars, holds of river (sea) vessels, etc.), a tandem of compatible foam concentrates and foam generators makes it possible to obtain a high expansion rate of foam that fills the protected object and promptly eliminates the fire. On the territory of Russia, the production and use of medium expansion foam, however, continues to remain relevant due to the massive use in practice of medium expansion foam generators.

Foam stability- the ability of the foam to retain its original properties.

Air-mechanical foam is designed to extinguish fires of liquid (fire class B) and solid (fire class A) combustible substances. Foam is a cellular-film dispersed system consisting of a mass of gas or air bubbles separated by thin liquid films.

Air-mechanical foam is obtained by mechanical mixing of the foaming solution with air. The main fire-extinguishing property of foam is its ability to prevent the flow of
into the combustion zone of combustible vapors and gases, as a result of which combustion stops. A significant role is also played by the cooling effect of fire extinguishing foams, which is largely inherent in low expansion foams containing a large amount of liquid.

An important characteristic of fire extinguishing foam is its multiplicity- the ratio of the foam volume to the volume of the foam concentrate solution contained in the foam. There are foams of low (up to 10), medium (from 10 to 200) and high (over 200) expansion . Foam barrels are classified depending on the ratio of the resulting foam (Fig. 2.36).

Rice. 2.36. Classification of foam fire nozzles

Foam barrel - a device for forming jets of air-mechanical foam of various expansion ratios from an aqueous solution of a foaming agent, installed at the end of a pressure line.

To obtain low expansion foam, manual air-foam barrels (SVP) and air-foam barrels with an ejected device (SVP) are used. They have the same device and differ only in size, as well as an ejector designed to suck the foam concentrate from the tank.

The trunk of the SVPE (Fig. 2.37) consists of a body 8 , on one side of which a pin connection head is screwed 7 for connecting the stem
a guide pipe is connected to the hose pressure line of the corresponding diameter, and on the other hand, a guide pipe is attached to the screws 5 , made of aluminum alloy and designed to form air-mechanical foam and direct it to the fire. There are three chambers in the barrel body: reception 6 , vacuum 3 and day off 4 . A nipple is located on the vacuum chamber 2 Ø 16 mm for hose connection 1 , having a length of 1.5 m, through which the foaming agent is sucked. At a working water pressure of 0.6 MPa, a vacuum is created in the chamber of the barrel body
not less than 600 mm Hg. Art. (0.08 MPa).

Rice. 2.37. Air-foam barrel with ejector type SVPE:

1 - hose; 2 - nipple; 3 – vacuum chamber; 4 – exit chamber;
5 – guide pipe; 6 - receiving chamber;

7 - connecting head; 8 - frame

The principle of foam formation in the SVP shaft (Fig. 2.38) is
next. Foaming solution passing through the hole 2 in the trunk 1 , creates in the cone chamber 3 underpressure, due to which air is sucked in through eight holes evenly spaced in the guide tube 4 trunk. The air entering the pipe is intensively mixed with the foaming solution and forms a jet of air-mechanical foam at the outlet of the barrel.

Rice. 2.38. Air-foam barrel (SVP):

1 - barrel body; 2 - hole; 3 – cone chamber; 4 - guide pipe

The principle of foam formation in the shaft of the SVPE differs from the SVP in that it is not a foaming solution that enters the receiving chamber, but water, which, passing through the central hole, creates a vacuum in the vacuum chamber. A foaming agent is sucked through the nipple into the vacuum chamber through a hose from a knapsack tank or other container. Technical characteristics of fire nozzles for obtaining low expansion foam are presented in Table. 2.24.

Table 2.24

To obtain medium expansion air-mechanical foam from an aqueous solution of a foaming agent and supply it to the fire seat, medium expansion foam generators (HPS) are used.

Depending on the performance of foam, the following standard sizes of generators are produced: GPS-200; GPS-600; GPS-2000. Their technical characteristics are presented in table. 2.25.

Table 2.25

Foam generators GPS-200 and GPS-600 are identical in design
and differ only in the geometric dimensions of the atomizer and housing. The generator is a portable water-jet ejector apparatus and consists of the following main parts (Fig. 2.39): nozzle 1 , grid package 2 , generator housing 3 with guiding device, manifold 4 and centrifugal atomizer 5 . The atomizer body is attached to the generator manifold with the help of three racks, in which the atomizer is mounted. 3 and coupling head GM-70. Grid package 2 is a ring covered with a metal mesh along the end planes (mesh size 0.8 mm). Centrifugal atomizer 3 has six windows located at an angle of 12°, which causes the flow of the working fluid to swirl and provides a spray jet at the exit. nozzles 4 designed to form a foam flow after a package of grids into a compact jet and increase the foam flight range. Air-mechanical foam is obtained by mixing three components in a generator in a certain proportion: water, foam concentrate and air. A stream of foaming agent solution under pressure is fed into the atomizer. As a result of ejection, when the sprayed jet enters the collector, air is sucked in and mixed with the solution. A mixture of droplets of foaming solution and air falls on the mesh package.

Rice. 2.39. Medium expansion foam generator GPS-600:

1 - nozzle; 2 – grid package; 3 – generator housing;

4 - collector; 5 - centrifugal atomizer

On the grids, deformed drops form a system of stretched films, which, closing in limited volumes, first form elementary (individual bubbles) and then bulk foam. The energy of newly arriving droplets and air pushes the mass of foam out of the foam generator.

test questions

1. Purpose and classification of fire hoses.

2. Design features of suction and pressure-suction hoses. Their functions. Application area.

3. Classification of fire hoses. features of their designs.

4. Analyze the head loss in the pressure hoses. Determination of head loss in hose lines.

5. Classification of hydraulic equipment. His appointment. Device.

6. Classification of fire nozzles. Appointment. Features of the supply of fire extinguishing agents.

7. Describe the design features of the RS-70 and KB-R barrels.

8. Purpose of fire monitors combined. Classification. Range of supply of water and foam jets.

9. Describe the difference in the principles of foam formation when supplying air-foam barrels of SVPE and SVP.

10. The device of medium expansion foam generators. The main indicators of their technical characteristics.

METHODOLOGY FOR CALCULATION OF FIRE EXTINGUISHING INSTALLATIONS WITH WATER, LOW AND MEDIUM EXPENSION FOAM

1. The initial data for the calculation of installations are the parameters given in paragraph 4.2.

2. In the area of ​​acceptance, packaging and dispatch of goods in warehouses with high-rise rack storage at a height of 10 to 20 m, the intensity and area values ​​\u200b\u200bfor calculating the consumption of water, foam concentrate solution for groups 5, 6 and 7, given in paragraph 4.2, must be increased at the rate of 10% for every 2 m of height.

3. The diameters of the pipelines of the installations should be determined by hydraulic calculation, while the speed of movement of water and foam concentrate solution in the pipelines should be no more than 10 m/s.

The diameters of the suction pipelines of the installations should be determined by hydraulic calculation, while the speed of water movement in the pipelines should be no more than 2.8 m / s.

4. Hydraulic calculation of pipelines should be performed under the condition that these installations are supplied with water only from the main water feeder.

5. The pressure at the control unit should be no more than 1.0 MPa.

6. Estimated consumption of water, foam concentrate solution, l  s -1, through the sprinkler (generator) should be determined by the formula

where is the performance coefficient of the sprinkler (generator), taken according to the technical documentation for the product; - free pressure in front of the sprinkler (generator), m of water. Art.

7. Minimum free head for sprinklers (sprinkler, deluge) with a conditional outlet diameter:

d y= 8...12 mm - 5 m w.c. Art.,

d y\u003d 15 ... 20 mm - 10 m of water. Art.

8. The maximum allowable head for sprinklers (sprinkler, deluge) is 100 m of water. Art.

9. The consumption of water, foaming agent solution must be determined by the product of the normative intensity of irrigation by the area for calculating the consumption of water, foaming agent solution, (see tables 1–3, section 4).

The water consumption for the internal fire water supply should be added to the water consumption for the automatic fire extinguishing installation.

The need to sum up the flow rates of water, foam solution of sprinkler and deluge installations is determined by technological requirements.

Table 1

Note. Pipes with parameters marked with * are used in outdoor water supply networks.

10. Head loss in the calculated section of pipelines, m, is determined by the formula

where is the flow rate of water, foaming agent solution at the design section of the pipeline, l  s -1 ; - pipeline characteristic, determined by the formula

where is the coefficient, taken according to Table 1; - length of the estimated section of the pipeline, m.

The head loss in the control units of the installations, m, is determined by the formula

where is the pressure loss coefficient in the control unit, is taken according to the technical documentation for the valves; – estimated consumption of water, foaming agent solution through control units, l  s -1 .

11. The volume of the foaming agent solution, m 3, during volumetric fire extinguishing is determined by the formula

where is the foam destruction coefficient, taken according to Table 2; - the estimated volume of the protected premises, m 3; - foam ratio.

table 2

Number of simultaneously operating foam generators № 1 is determined by the formula

where - the performance of one generator for the solution of the foaming agent, m 3  min -1;

- the duration of the installation with medium expansion foam, min, is taken according to table 2.

12. The duration of operation of internal fire hydrants equipped with manual water or foam fire nozzles and connected to the supply pipelines of the sprinkler installation should be taken equal to the operating time of the sprinkler installation. The duration of operation of fire hydrants with foam fire nozzles, fed from independent inputs, should be taken equal to 1 hour.

Method for calculating the parameters of fire extinguishing installations

high expansion foam

1. The estimated volume is determined V(m 3) of the protected premises or the volume of local fire extinguishing. The estimated volume of the room is determined by the product of the floor area by the height of filling the room with foam, with the exception of the volume of solid (impermeable) non-combustible building elements (columns, beams, foundations, etc.).

2. The type and brand of the high-expansion foam generator is selected and its performance is set by foaming agent solutionq(dm 3 min -1).

3. The estimated number of high-expansion foam generators is determined

where a- coefficient of destruction of the foam;  is the maximum time for filling the volume of the protected room with foam, min; K- foam ratio.

The value of the coefficient a is calculated by the formula:

a = K 1  To 2  To 3 (2),

where K 1 - the coefficient taking into account the shrinkage of the foam, is taken equal to 1.2 for a room height of up to 4 m and 1.5 - for a room height of up to 10 m. At a room height of more than 10 m, it is determined experimentally.

To 2 - takes into account foam leaks; in the absence of open openings, it is taken equal to 1.2. In the presence of open openings, it is determined experimentally.

To 3 - takes into account the effect of flue gases on the destruction of the foam. To take into account the effect of combustion products of hydrocarbon liquids, the value of the coefficient is assumed to be -1.5. For other types of fire load is determined experimentally.

The maximum time for filling the volume of the protected room with foam is assumed to be no more than 10 minutes.

4. The performance of the system is determined by the solution of the foaming agent, m 3 s -1:

5. According to the technical documentation, the volume concentration of the foaming agent in the solution is established c, (%).

6. Determined estimated quantity foam concentrate, m 3:

. (4)

APPENDIX 3 (Revision, Rev. No. 1)

APPENDIX 4 (Deleted, Rev. No. 1)

APPENDIX 5

Mandatory

INITIAL DATA FOR CALCULATION OF THE MASS OF GAS EXTINGUISHING AGENTS

Normative volumetric fire extinguishing concentration of gaseous nitrogen (No. 2).

Gas density at R= 101.3 kPa and T\u003d 20 С is 1.17 kg  m -3.

Table 1

Normative volumetric fire extinguishing concentration of gaseous argon (Ar).

Gas density at R= 101.3 kPa and T\u003d 20 С is 1.66 kg  m -3.

table 2

Normative volumetric fire extinguishing concentration of carbon dioxide (CO 2).

Vapor density at R= 101.3 kPa and T\u003d 20 С is 1.88 kg  m -3.

Table 3

Normative volumetric fire extinguishing concentration of sulfur hexafluoride (SF 6).

Vapor density at P= 101.3 kPa and T\u003d 20 С is 6.474 kg  m -3.

Table 4

Normative volumetric fire extinguishing concentration of freon 23 (CF 3 H).

Vapor density at R= 101.3 kPa and T\u003d 20 С is 2.93 kg  m -3.

Table 5

Normative volumetric fire extinguishing concentration of freon 125 (C 2 F 5 H).

Vapor density at R= 101.3 kPa and T\u003d 20 С is 5.208 kg  m -3.

Table 6

Normative volumetric fire extinguishing concentration of freon 218 (C 3 F 8).

Vapor density at R= 101.3 kPa and T\u003d 20 С is 7.85 kg  m -3.

Table 7

Normative volumetric fire extinguishing concentration of freon 227ea (C 3 F 7 H).

Vapor density at R= 101.3 kPa and T\u003d 20 С is 7.28 kg  m -3.

Table 8

Normative volumetric fire extinguishing concentration of freon 318 C (C 4 F 8c).

Vapor density at R= 101.3 kPa and T\u003d 20 С is 8.438 kg  m -3.

Table 9

Normative volumetric fire extinguishing concentration of the gas composition "Inergen" (nitrogen (No. 2) - 52% (vol.); argon (Ar) - 40% (vol.); carbon dioxide (CO 2) - 8% (vol.)).

Vapor density at R= 101.3 kPa and T\u003d 20 С is 1.42 kg  m -3.

Table 10

Question No. 1. Fundamentals of foam extinguishing: foams, foaming agents, wetting agents, their purpose, types, composition, physical and chemical properties and scope. Safety measures when working with foam concentrates.

Types of foam, their composition, physicochemical and fire-extinguishing properties,

The procedure for obtaining and scope.

Foam - a dispersed system consisting of cells - air (gas) bubbles separated by liquid films containing a foam stabilizer.

Types of foam by production method:

- chemical foam- obtained as a result of a chemical reaction of alkaline and chemical components (the released carbon dioxide foams an aqueous alkaline solution);

- air-mechanical foam- obtained by mechanical mixing of the foaming solution with air.

Physico-chemical properties of the foam:

- stability- the ability of the foam to retain its original properties (to resist destruction for a certain time);

- multiplicity- the ratio of the foam volume to the volume of the foaming agent solution contained in the foam;

- viscosity- the ability of the foam to spread over the surface;

- dispersion- the degree of crushing of the bubbles (the size of the bubbles);

- electrical conductivity- the ability to conduct electricity.

Fire extinguishing properties of foam:

- insulating action(foam prevents the entry of combustible vapors and gases into the combustion zone, as a result of which combustion stops);

- cooling effect(largely inherent in low expansion foam containing a large amount of liquid).

Types of foam by multiplicity:

- low expansion foam- foam ratio from 4 to 20 (obtained with SVP trunks, foam draining devices);

- medium expansion foam- foam ratio from 21 to 200 (obtained by GPS generators);

- high expansion foam- more than 200 foam expansion (obtained by forced air injection).

Application area.

Foam is widely used to extinguish fires of solid (class A fires) and liquid substances (class B fires) that do not interact with water, and, first of all, to extinguish fires of oil products.

Advantages of foam as an extinguishing agent:

Significant reduction in water consumption;

Ability to extinguish fires of large areas;

Possibility of volume extinguishing;

Possibility of subsurface extinguishing of oil products in tanks;

Increased (compared to water) wetting ability.

When extinguishing with foam, simultaneous overlapping of the entire combustion mirror is not required, since the foam is capable of spreading over the surface of the burning material.

Foam concentrates: purpose, classification, types, composition,

Properties, storage rules and quality control.

Foaming agent (foam concentrate) - a concentrated aqueous solution of a foam stabilizer (surfactant), which, when mixed with water, forms a working solution of a foaming agent.

Foam concentrates are designed to produce air-mechanical foam or wetting agent solutions using fire equipment, used to extinguish fires of classes A (combustion of solid substances) and B (combustion of liquid substances).

Foaming agents, depending on the chemical composition (surfactant base), are divided into: synthetic (s), fluorosynthetic (fs), protein (p), fluoroprotein (fp).

Types of foaming agents depending on the ability to form fire-extinguishing foam on standard fire equipment:

Foam concentrates for extinguishing fires with low expansion foam (foam expansion from 4 to 20);

Foam concentrates for extinguishing fires with medium expansion foam (foam expansion from 21 to 200);

Foam concentrates for extinguishing fires with high expansion foam (foam expansion more than 200).

Foam concentrates, depending on their applicability for extinguishing fires of various classes according to GOST 27331, are divided into:

Foam concentrates for extinguishing class A fires;

Foam concentrates for extinguishing class B fires.

Foaming agents, depending on the possibility of using water with a different content of inorganic salts, are divided into types:

Foam concentrates for producing fire-extinguishing foam using potable water;

Foam concentrates for producing fire-extinguishing foam using hard water;

Foam concentrates for producing fire-extinguishing foam using sea water.

Foaming agents, depending on the ability to decompose under the action of the microflora of water bodies and soils, according to GOST R 50595, are divided into: rapidly degradable, moderately degradable, slowly degradable, extremely slowly degradable.

Classes of foam concentrates for extinguishing fires according to the totality of indicators of purpose:

1 - film-forming foam concentrates designed to extinguish fires of water-insoluble combustible liquids by supplying low-expansion foam to the surface and to the oil product layer;

2 - foam concentrates designed to extinguish fires of water-insoluble combustible liquids by soft supply of low expansion foam;

3 - special-purpose foam concentrates designed to extinguish fires of water-insoluble combustible liquids by supplying medium expansion foam;

4 - general-purpose foam concentrates designed to extinguish fires of water-insoluble combustible liquids with medium expansion foam and extinguish fires of solid combustible materials with low expansion foam and an aqueous solution of a wetting agent;

5 - foam concentrates designed to extinguish fires of water-insoluble combustible liquids by supplying high expansion foam;

6 - foam concentrates designed to extinguish fires of water-insoluble and water-soluble combustible liquids.

Foam concentrates have a symbol, which indicates:

Foam class;

Type of foaming agent;

The value of the concentration of the foaming agent in the working solution;

The chemical nature of the foaming agent.

Foam concentrates of class 1, 2, 3, 4, 5 and 6 in the symbol have the index 1H, 2H, 3C, 4C, 5B and 6, respectively.

Foam concentrates of class 1 and 2, which form fire-extinguishing foam of medium and high expansion, in the symbol have the index, respectively, 1NSV and 2NSV.

Foam concentrates of class 1 and 2, which form fire-extinguishing foam of medium expansion, in the symbol have the index, respectively, 1HC and 2HC.

Foam concentrates of class 1 and 2, which form fire-extinguishing high-expansion foam, have the index 1NVi and 2NV, respectively, in the symbol.

Class 3 foam concentrates that form fire-extinguishing high-expansion foam have the index 3CB in the symbol.

If a foam concentrate of class 6 is capable of forming fire-extinguishing foam of low, medium and high expansion, its symbol indicates the corresponding index H, C, B. The absence of an appropriate index means that the foam concentrate is not recommended for extinguishing fires with foam of this expansion.

When the manufacturer recommends using a class 6 foaming agent when extinguishing water-insoluble and water-soluble combustible liquids with different concentrations, its symbol indicates the concentration of the foaming agent in the working solution when extinguishing water-insoluble and water-soluble combustible liquids.

An example of a foam concentrate symbol 2 NSV - 6 fs

Checking the quality of foam concentrates and determining the foam ratio.

To determine the foam ratio, a 2-6% solution of a foaming agent is poured into a glass graduated cylinder with a capacity of 1000 cm 3, closed with a cork and, holding it in a horizontal position with both hands, shake it in the direction of the longitudinal axis for 30 s. After shaking, the cylinder is placed on the table, the cork is removed and the volume of foam formed is counted. The ratio of the resulting volume of foam to the volume of the solution expresses the multiplicity of the foam. Sustainability foam depends on the time during which the foam, obtained by the method of determining the multiplicity, is destroyed by 2/5 of the original volume.

The quality indicators of foam concentrates during their storage in fire departments and at protected facilities equipped with fire extinguishing systems are checked after the expiration of the warranty period, and then at least 1 time in 6 months (PO-3NP, Foretol, "Universal" - at least 1 time per 12 months). The analysis of indicators is carried out in accredited organizations in accordance with GOST R 50588-93 “Foam concentrates for extinguishing fires. General technical requirements and test methods". A decrease in the value of indicators below the established norms by 20% is the basis for the write-off or regeneration (restoration of the original properties) of the foam concentrate.

Foam - it is an accumulation of bubbles, which contributes mainly due to the effect of surface quenching. Bubbles are created when water is mixed with a foaming agent. Foam is lighter than the lightest flammable oil product, so when applied to a burning oil product, it remains on its surface.

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Types of foam by multiplicity:

• low expansion foam - foam expansion from 4 to 20 (obtained with SVP trunks, foam draining devices);
• medium expansion foam - foam expansion from 21 to 200 (obtained by GPS generators);
• high expansion foam - more than 200 foam expansion (obtained by forced air injection).

Application area. Advantages and disadvantages

Foam is widely used to extinguish fires of solid (class A fires) and liquid substances (class B fires) that do not interact with water, and, first of all, to extinguish fires of oil products.

chemical foam It is formed by mixing an alkali (usually sodium bicarbonate) with an acid (usually aluminum sulfate) in water. These substances are contained in one sealed container. To make the foam more durable and extend its life, a stabilizer is added to it.

When these chemicals interact, bubbles are formed filled with carbon dioxide, which in this case practically does not have any fire extinguishing ability; its purpose is to make the bubbles float.

The powder can be stored in containers and introduced into the water during fire fighting through a special funnel, or each of the two chemicals can be pre-mixed with water, resulting in an aluminum sulfate solution and a sodium bicarbonate solution.

This foam is formed from a foam solution obtained by mixing a blowing agent with water. Bubbles are generated by turbulent mixing of air with foam solution. As the name of the foam suggests, its bubbles are filled with air. The quality of the foam depends on the degree of mixing, as well as on the performance and efficiency of the equipment used, and its quantity depends on the design of this equipment.

There are several types of air-mechanical foam, identical in nature, but with different fire-extinguishing efficiency. Its foaming agents are produced on the basis of protein and surfactants. Surfactants are a large group of substances including detergents, wetting agents and liquid soaps.

Restrictions on the use of foam

When used correctly, foam is an effective fire extinguishing agent. However, there are certain limitations in its use, which are listed below.

1. Since the foam is an aqueous solution, it conducts electricity, so it should not be applied to live electrical equipment.
2. Foam, like water, cannot be used to extinguish combustible metals.
3. Many types of foam should not be used with fire extinguishing powders. The exception to this rule is "light water", which can be used with extinguishing powder.
4. Foam is not suitable for extinguishing fires associated with the combustion of gases and cryogenic liquids. But high-expansion foam is used to extinguish spreading cryogenic liquids to quickly heat vapors and reduce the danger associated with such spreading.

1. Despite the existing limitations in use, the foam is very effective in fighting.
2. Foam is a very effective fire extinguishing agent, which, in addition, has a cooling effect.
3. The foam creates a vapor barrier that prevents flammable vapors from escaping to the outside. The surface of the tank can be covered with foam to protect it from a fire in an adjacent tank.

4. Foam can be used to extinguish class A fires due to the presence of water in it. "Light water" is especially effective.

5. Foam is an effective fire extinguishing agent for covering spreading oil products. If the oil leaks out, one should try to close the valve and thus interrupt the flow. If this is not possible, the flow should be blocked with foam, which should be applied to the area of ​​the fire to extinguish it and then to create a protective layer covering the seeping liquid.

6. Foam is the most effective extinguishing agent for extinguishing fires in large containers with.

7. Fresh or hard or soft water can be used to produce foam.

Compression foam deserves special attention, which has proven itself very well in extinguishing fires.

Compressed air foam system (CAFS) is a technology used in firefighting to deliver firefighting foam to extinguish a fire or protect an area where there is no combustion from igniting.

The compressible foam is obtained from a standard pumping unit which has a compressed air inlet point into the frother to form the foam. In addition, compressed air also adds energy to the jet, which allows for a longer delivery range of OTV compared to standard foam generators or barrels.

When using compression foam, the effectiveness of the extinguishing agent is about 80%. This indicator is possible due to the special physical properties of compression foam, namely adhesiveness. When extinguishing a fire, the fireman gets new opportunities in his arsenal. When applied to the ceiling and walls, the foam isolates adjacent rooms from exposure to high temperatures, while the foam keeps for a long time even on vertical surfaces: from one hour on metal to two to three hours on wood. Each bubble of compression foam has a strong bond with its neighbors, which leads to high foam stability. The result is a thin (about 1-2 centimeters) and durable "blanket", which literally "covers" the burning surface, stopping the access of oxygen to the source of ignition.

Ready-made compression foam is fed through pressure fire hoses with a diameter of 38 or 51 mm at a working pressure of 7 ÷ 10 kgf/cm 2 .

The physical parameters of the compression foam and, accordingly, the fire-extinguishing properties of the foam are changed by changing the ratio of ingredients. "Raw" (heavy) foam with a ratio of 1:5 (water:air) and "dry" (light) foam with a ratio of up to 1:20 (water:air) can be produced.

Delivery of compression foam with a ratio of 1:10 (water:air) to vertical surfaces

(metal door, brick wall).

At the same time, the foam also has the best properties of water - it cools the hearth, and thanks to the wetting agents included in its composition, it penetrates into the pores and cracks of the surface, preventing the material from smoldering and re-igniting.

The main advantages of compression foam are: quick knocking down of the flame and lowering the temperature, reduction of extinguishing time by 5 ÷ 7 times (by 500 ÷ 700% !!!), reduction of water consumption by 5 ÷ 15 times (by 500 ÷ 1500%).

Foaming agents

Foaming agent (foam concentrate)- a concentrated aqueous solution of a foam stabilizer (surfactant), which, when mixed with water, forms a working solution of a foaming agent.

Foam concentrates are designed to produce air-mechanical foam or wetting agent solutions using fire equipment, used to extinguish fires of classes A (combustion of solid substances) and B (combustion of liquid substances).

Foaming agents, depending on the chemical composition (surfactant base), are divided into:

• synthetic (s),
• fluorosynthetic (fs),
• protein (p),
• fluoroprotein (fp).

Foam concentrates, depending on the ability to form fire-extinguishing foam on standard fire equipment, are divided into:

The most popular and inexpensive, and at the same time effective, today are foam concentrates marked PO-6 and PO-3. The numbers on the marking indicate the level of concentration of the foaming agent in the working solution (6 or 3 liters per certain volume of water). Store such products in heated rooms. Freezing, the foaming agent does not lose its properties and is again ready for use after defrosting, but in the conditions of a fire that has arisen, there may simply not be time to bring it to the desired consistency. Both types are biodegradable and absolutely safe for storage and transportation.

CHARACTERISTICS OF THE MOST COMMON FOAM EXPERTS

PO-6NP - synthetic, biodegradable. Designed to extinguish fires of oil products, GZh, for use with sea water. Morpen is synthetic and biodegradable. Designed to produce fire extinguishing foam of low, medium and high expansion using both fresh and sea water.