For medium expansion foam

Combined for low and medium expansion foam

Rice. 3.23. Classification of foam fire nozzles

Foam shaft - a device installed at the end of the pressure line for the formation of jets of air-mechanical foam of various multiplicity from an aqueous solution of a foaming agent.

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

The trunk of the SVPE (Fig. 3.24) consists of a body 8 , on one side of which a pin connection head is screwed 7 for connecting the barrel to a hose pressure line of the corresponding diameter, and on the other hand, a 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 of at least 600 mm Hg. Art. (0.08 MPa).

Rice. 3.24. 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 trunk (Fig. 3.25) is as follows. 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. 3.25. Barrel air-foam SVP:

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

The principle of foam formation in the shaft of the SVP 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 barrel or other container. Technical characteristics of fire nozzles for obtaining low expansion foam are presented in Table. 3.10.

Table 3.10

Medium expansion foam generators are used to obtain medium expansion air-mechanical foam from an aqueous solution of a foaming agent and supply it to the fire site.

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. 3.11.

Table 3.11

Foam generators GPS-200 and GPS-600 are identical in design and differ only in the geometrical dimensions of the atomizer and housing. The generator is a portable water-jet ejector apparatus and consists of the following main parts (Fig. 3.26): generator body 1 with guiding device, mesh package 2 , centrifugal atomizer 3 , nozzle 4 and collector 5 . The atomizer housing 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). Swirl type atomizer 3 has six windows located at an angle of 12 °, which causes the flow of the working fluid to swirl and provides an atomized 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. 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.

As foam fire nozzles of the combined type, we consider the installation of combined fire extinguishing (UKTP) "Purga", which can be manual, stationary and mobile. They are designed to produce low and medium expansion air-mechanical foam. Technical characteristics of UKTP of various designs are presented in Table. 3.12. In addition, a range diagram and an irrigation map (Fig. 3.27) have been developed for these trunks, which makes it possible to more clearly assess their tactical capabilities in extinguishing fires.

Table 3.12

RUSSIANJOINT STOCKSOCIETYENERGY
ANDELECTRIFICATION « EECRUSSIA»

DEPARTMENTSCIENCEANDTECHNIQUES

INSTRUCTIONS
BY OPERATIONSINSTALLATIONS
FIRE FIGHTING WITHAPPLICATION
AIR - MECHANICALFOAM

RD 34.49.502-96

ORGRES

Moscow 1996

DevelopedJoint-stock company "Firm for adjustment, improvement of technology and operation of power plants and networks" ORGRES ".

PerformersYES. ZAMYSLOV, A.N. IVANOV, A.S. KOZLOV, V.M. OLD MAN

Agreedwith the Department of the General Inspectorate for the Operation of Power Plants and Grids of RAO "UES of Russia" 16.04.96

Chief engineer A.D. Shcherbakov

ApprovedDepartment of Science and Technology of RAO "UES of Russia" 17.04.96

Head A.P. BERSENEV

Expiry date set

from 01.01.97

This Instruction sets out the basic requirements for the operation of stationary automatic foam fire extinguishing installations installed at energy enterprises.

A schematic diagram of a fire extinguishing installation is given. The conditions for storage of foam concentrates and their aqueous solutions are described. The technical requirements for the operation of equipment for fire extinguishing installations as a whole and their individual elements are outlined.

The procedure for organizing testing and commissioning of newly installed fire extinguishing installations and the procedure for conducting inspections of the technical condition of equipment, apparatus and devices of the fire extinguishing installation and the timing of the revision of the entire installation were determined.

Typical malfunctions that may occur during the operation of a fire extinguishing installation are described, and recommendations are given for their elimination.

The main safety requirements for the operation of foam fire extinguishing installations are indicated.

The forms of acts of flushing and hydraulic testing of pressure and distribution pipelines of fire extinguishing installations, the form of the register of maintenance and repair of the fire extinguishing installation, the form of the act of carrying out fire tests are given.

With the release of this Instruction, the “Instruction for the operation of fire extinguishing installations using air-mechanical foam” (M: SPO Soyuztekhenergo, 1980) becomes invalid.

1. INTRODUCTION

1.1 . Air-mechanical foam is the most effective fire-extinguishing agent for extinguishing fires of classes A (combustion of solid substances) and B (combustion of liquid substances).

1.2 . To obtain air-mechanical foam, foam concentrates and fire fighting equipment are used. Depending on the field of application, foam concentrates are divided into two classification groups: general and special purpose. General-purpose foam concentrates include: PO-3NP, PO-3AI TEAS. Targeted foam concentrates include: "Sampo", "Marine", "Potok", "Film-forming", "Foretol", "Universal", POF-9M.

Special purpose foam concentrates differ from general purpose foam concentrates in their higher fire-extinguishing capacity due to the use of secondary additives.

All foam concentrates of general and special purpose do not lose their original physical and chemical properties during repeated freezing and subsequent gradual thawing.

In power plants, general-purpose foam concentrates are mainly used.

1.3 . To extinguish fires at transformers and reactors, air-mechanical low expansion foam is used, at fuel oil and oil facilities - medium expansion foam.

Low-expansion foam is obtained using OPDR foam sprinklers and its modifications.

To obtain medium expansion foam, medium expansion foam generators GPS-200, GPS-600, GPS-2000 and stationary medium expansion foam generators GPSS-600, GPSS-2000 can be used.

1.4 . In this Instruction, the following terms, definitions and established abbreviations are adopted:

AUPP - automatic foam fire extinguishing installation;

AUPS - automatic fire alarm installation;

NPPT - foam fire extinguishing pump;

NKR - concentrated solution pump;

OPDR - rosette foam deluge sprinkler;

GPS - medium expansion foam generator;

GPSS - stationary medium expansion foam generator;

Main control room - main control panel;

PU - control panel;

KR - concentrated solution;

ON - foaming agent;

PI - fire detector;

OK - check valve;

Main control room - block control panel.

2. GENERAL PROVISIONS

2.1 . This Instruction is the main technical document used to develop local instructions for the operation of specific fire extinguishing installations with air-mechanical foam installed at power enterprises.

2.2 . The local operating instructions for a specific fire extinguishing installation with air-mechanical foam are developed by the organization that commissioned this installation, together with the power company where it is used. If the adjustment was carried out by a power company, then the instruction is developed by the personnel of this enterprise.

2.3 . When developing local instructions, in addition to this Instruction, it is necessary to take into account the requirements of design and technical documentation for equipment, instruments and apparatus that are part of the fire extinguishing installation.

2.4 . The local instructions should include the relevant labor protection requirements and environmental protection measures that ensure the safety of operation, technical supervision and repair work on a specific fire extinguishing installation for personnel.

2.5 . The local instruction must be reviewed at least once every three years and every time after the reconstruction of the foam fire extinguishing installation or in the event of a change in operating conditions.

3. SAFETY MEASURES DURING AUPP OPERATION

3.1 . All rotating parts of PPT, NKR pumps must be protected by protective covers.

It is forbidden to clean and wipe the pumps during their operation.

3.2 . The electrical equipment of the pumps must have a good fixed ground.

3.3 . The inclusion of equipment in operation, operations with fittings, sampling of concentrated foam concentrate and its solution must be carried out by at least two persons from service sites.

3.4 . When working with foam concentrates, precautions must be taken. Contact with concentrated foaming agent on unprotected skin causes irritation. Exposure to the mucous membrane of the eyes leads to irritation and burns.

Work with foam concentrates should be carried out in rubberized gloves, and eyes and face should be protected with protective shields or goggles.

If the foaming agent gets on the skin, and especially on the mucous membrane of the eyes, they should be quickly washed with plenty of running water.

3.5 . Repair work at the foam fire extinguishing station and the system should be carried out only in parallel.

3.6 . For the period of stay in the cable rooms of personnel (bypass, repair work, etc.), the start-up of the fire extinguishing installation is transferred to the remote control mode. Upon completion of work in the protected premises, the automatic operation of the foam fire extinguishing installation is restored.

3.7 . When operating the process equipment of foam fire extinguishing installations, the personnel of power enterprises must comply with the established safety requirements set forth in the PTE, PPB, PTB and in the factory passports and operating instructions for specific equipment.

3.8 . It is forbidden to drain the foaming agent and its solutions into sewer systems and storm drains.

4. ORDER OF OPERATION OF AUPP

4.1 . Automatic foam fire extinguishing installation (AUPP) is designed to extinguish fires in the protected premises and facilities of the power plant upon receipt of a signal about its occurrence from fire detectors.

All equipment must be painted in standard colors and clearly marked.

4.2 . A schematic diagram of a fire extinguishing installation with air-mechanical foam is shown in the figure.

Schematic diagram of a fire pumping station with the supply of finished foam solution:

1 - storage tanks for foaming agent solution; 2 - pumps for supplying a foaming agent solution; 3 - pumps for supplying a foaming agent to the tank, a foaming agent solution to a pulse device, circulation of a solution, a foaming agent; 4 - impulse device (pneumatic tank); 5 - compressor;

gate valve; - check valve.

Pipelines: foam solution

plumbing

foaming agent

solution circulation

compressed air

To measure the characteristics of foam generators or foam sprinklers under various operating modes, it is recommended to install a special outlet on the pressure pipeline between the pump and the valve closest to the pump in the fire extinguishing installation diagram,equipped at the end with a valve and a device for connecting a foam generator or foam sprinkler.

4.3 . The automatic foam fire extinguishing installation includes the following main equipment:

a container for storing a concentrate of a foaming agent or a tank for storing an aqueous solution of a foaming agent;

source of water supply (special reservoir or water supply);

pipeline network;

pumps for the intake and supply of water or a ready-made aqueous solution of a foaming agent;

locking and starting devices;

automatic control system (including fire alarm);

foam generators or foam sprinklers;

electrical measuring instruments.

In addition to the listed main equipment, the following can be included in the AUPP scheme:

metering pumps for supplying the calculated amount of foam concentrate to pressure and distribution pipelines;

water tank for filling feed pumps;

pneumatic tank to maintain constant pressure in the AUPP network;

compressor for air supply to the pneumatic tank.

4.4 . Before filling the tanks for storage of the foaming agent solution, it is necessary to carry out their internal inspection and cleaning. After that, use pumps to fill the container with water and concentrated foaming agent in proportions to obtain the required composition of the foaming agent solution.

4.5 . Turn on the foam fire extinguishing pump for recirculation to mix the solution in the tanks for 15 - 20 minutes. At the same time, it is controlled: leakage of the solution through the water-indicating glasses of the tanks, the absence of leaks in the circuit, the level of the foaming agent in the tanks.

After that, the solution is analyzed with an entry in the operational log.

4.6 . The launch of the AUPP should be automatic. The transfer of the foam extinguishing installation to the remote and manual switching on mode is not allowed, except for cases when the installation is being repaired.

Automatic start is carried out from the impulse of fire detectors installed in the protected premises (structures).

4.7 . Remote start-up of the AUPP is carried out by a button or a manual switch key installed on special panels or cabinets of the control panel (main, block, thermal, etc.). Remote start is provided for duplication of automatic start.

4.8 . Devices for local start-up of the fire extinguishing installation are located in the pumping station room and at the control units of distribution pipelines and are designed to test and adjust the fire extinguishing installation, as well as to start the installation in case of failures of automatic and remote starts.

4.9 . The control panel should contain a diagram of this installation with a brief description of the device and operation of the AUPP. In the Pumping Station Premises there should be an instruction on the order of putting the pumps into operation and opening the shut-off valves, as well as a schematic and technological diagram.

4.10 . On the control units, AUPP equipment there must be appropriate visual diagrams, inscriptions and signs.

4.11 . To obtain air-mechanical foam of medium expansion, foam generators GPS-200, GPS-600 and GPS-2000 are used, the technical characteristics of which are given in Table. .

Table 1

Air-mechanical foam is formed as a result of intensive mechanical mixing of an aqueous solution of a foaming agent with air.

Foaming agents PO-1 and PO-6 are used to produce foam.

Foaming agent PO-l is a neutralized kerosene contact containing at least 45% sulfonic acids. To obtain the necessary multiplicity and stability of the foam, 4.5% glue and 10% alcohol or ethylene glycol are added to it.

Foaming agent PO-6 is a product of alkaline hydrolysis of technical blood of animals. To give foam stability, 1% ferrous sulfate is added to it. To prevent rotting of the foaming agent during long-term storage, 4% sodium fluoride is added to it.

Foam concentrates must meet the requirements of GOST 6948-54 and GOST 9603-61.

Air-mechanical foam consists of bubbles, the shell of which is formed from a foaming agent solution. The bubbles contain (depending on the foaming agent) up to 90% air, 9.5% water and up to 0.5% foaming agent. The specific gravity of the foam is from 0.11 to 0.17.

It turns out air-mechanical foam with the help of special devices (mixers and air-foam barrels). The durability of the foam based on the PO-1 foam concentrate is 30 minutes, and on the basis of the PO-6 foam concentrate it is at least 60 minutes.

VNIIPO has developed a formula for foaming agent PO-8 to obtain an air-mechanical foam of increased resistance, which is used to extinguish oil products and polar liquids (alcohol, acetone, etc.).

Air-mechanical foam according to the output ratio is divided into normal and high expansion foam.

Foam of normal expansion is considered when from 200 to 300 liters of foam is formed from 1 liter of foam concentrate PO-1 and 25 liters of water, from 125 to 175 liters from 1 liter of foam concentrate PO-6 and 25 liters of water.

Foam from foam concentrate PO-6 is more stable than from foam concentrate PO-1. To obtain foam of normal expansion, aqueous solutions of foaming agents PO-1 (3-4% by volume) and PO-6 (4-6% by volume) are used.

Foaming agent PO-1 is considered suitable if the foam output ratio is at least 10, its durability is at least 30 minutes, and foam concentrate PO-6, if the foam output ratio is at least 5, its durability is at least 60 minutes.

Normal expansion foam holds well on vertical surfaces, so it can be used to protect materials and structures from fire when exposed to radiant heat.

It is advisable to use air-mechanical foam of normal expansion to extinguish oil products with a flash point of 45 ° C and above, located in containers, and oil products with a flash point of 45 ° C and below (with the exception of aviation gasoline), spilled in a thin layer over a hard cover or on the surface of water .

It can also be used to extinguish oil products with a flash point of 45 ° C and below (with the exception of gasoline) in containers. But at the same time, it must be remembered that to extinguish oil products with a flash point of 28 ° C and below on an area of ​​\u200b\u200bnot more than 100 m 2 it is possible to use air-mechanical foam of normal expansion based on foam concentrate PO-1, and on an area of ​​​​not more than 400-500 m 2 - based on foaming agent PO-6. The distance from the upper edge of the side of the tank to the liquid surface should be no more than 2 m. This condition should also be observed when extinguishing oil products with a flash point of 28 to 45 ° C.

Foam concentrates are ineffective in extinguishing fires of polar liquids (alcohol, ether, acetone).

To extinguish oil products (gasoline, kerosene, crude oil, fuel oil), along with foaming agent PO-1, NB wetting agent is used.

VNIIPO has developed a method for extinguishing oil products in containers by supplying air-mechanical foam through a layer of fuel. In this case, the fire can be extinguished at any level of fuel in the tanks.

High expansion foam based on PO-1 or PO-6 foam concentrates is produced by a special generator operating on the principle of enhanced air suction. It can be used for localization of fires of solid substances, fiery combustion in rooms. Foam gives high fire-extinguishing efficiency when extinguishing oil products.

When it extinguishes fiery combustion in the premises, smoke and combustion products are displaced, the combustion centers are localized, and favorable conditions are created for the complete cessation of combustion.

As the rooms are filled with high-expansion foam, the temperature in them quickly decreases as a result of the displacement of hot gases, the cessation of combustion and the partial cooling of structures. The temperature in a burning room, as practice shows, immediately after foam is supplied to it, it can drop from 1000 ° C or more to 65-50 ° C.

After filling the room with foam, the temperature in it may rise again, since the heated floor structures do not have time to cool due to the short-term action of the foam.

High-expansion foam can only extinguish a flame due to the presence of a large amount of air in it and the limited time of its supply. The centers of smoldering of solids remain unextinguished.

Under the influence of the heat released during smoldering, the foam quickly collapses.

The complete elimination of smoldering centers depends on the intensity and time of foam supply and on how quickly it penetrates to the combustion sites.

In practice, high expansion foam is not thermally conductive. Fluctuations in ambient temperature from -30 to +30°C do not have a significant effect on the quality of the foam. At low temperatures (below -15 ° C), the foam resistance is somewhat reduced, although a stable crust forms on its surface. High temperature accelerates the destruction of the foam.

Foam does not have a harmful effect on most materials and equipment, does not create additional load on structures due to its low volumetric weight.

The foaming solution is a good wetting agent and therefore freely penetrates into materials, including fibrous ones.

When using air-mechanical foam, the work of firefighters during fire extinguishing is greatly facilitated. Therefore, it is widely used in fire fighting, it is the main fire extinguishing agent.

When extinguishing oil products, it is necessary to use the calculated amount of both chemical and air-mechanical foam. Instructions for their calculation are set out in Appendix 4 of the “Fire Safety Rules for River Transport of the Ministry of the River Fleet of the RSFSR”.

Carbonic acid (technical name for carbon dioxide) C0 2 - a colorless gas with a barely perceptible odor, does not burn and does not support combustion, does not conduct electricity. The extinguishing concentration of carbon dioxide vapor in the air should be 22.4% (by volume). At 0°С and pressure 36 kgf/cm 2 easily liquefies from a gaseous to a liquid state.

The heat of vaporization of liquid carbon dioxide is 47.7 cal/kg. With the rapid evaporation of liquid carbon dioxide, solid (snow-like) carbon dioxide is formed. The specific gravity of such carbon dioxide at a temperature of -79 ° C is 1.53.

Carbon dioxide or carbon dioxide snow directed into the fire zone reduces the oxygen concentration in it to such a value that combustion is impossible, and also cools the burning substance and the environment, as a result of which combustion stops.

Carbon dioxide is used to extinguish fires in enclosed spaces (under conditions of limited air exchange) and in a relatively small area directly in the air. It is used to extinguish fires in energized electrical installations.

When extinguishing fires in enclosed spaces, 0.495 kg / m 3 carbon dioxide, and in the most fire hazardous rooms -0.594 / kg / m 3 .

Flame combustion in the cargo hold of a vessel when carbon dioxide is used stops when the percentage of oxygen in it decreases to 14%. The smoldering, however, continues. To stop it, the oxygen content in the hold must be increased to 5%. Carbon dioxide must be fed into the hold until the smoldering completely stops, and it can last from several hours to one or two days.

Carbon dioxide as an independent fire extinguishing agent "is rarely used in stationary fire-fighting installations on river transport. It is replaced by more effective agents - halocarbons: ethyl bromide, methylene bromide, tetrafluorodibromoethane, which are included in the composition of such fire extinguishing mixtures as" 3.5", SZhB and one-component freon-114B2.

Introduction

Foam concentrates

Types of foam concentrates

Foam concentrate dispensers

Foam storage

Conclusion

List of sources

Introduction

The theme of my work: "Features of the use of air-mechanical foam for extinguishing fires."

My work is to tell and explain what air-mechanical foam is, how and where it is used, as well as the types of foams and methods of foaming.

Foam fire extinguishing in the oil and gas industry is the most popular, effective, and sometimes the only possible one. To protect objects, in fact, all types of air-mechanical foams are used: foam of low, medium and high expansion. In this case, foaming agents are used in accordance with their purpose, chemical composition, and method of supply.

Thus, it is possible to outline trends for improving foam extinguishing

· creation of new modern foam concentrates;

· Creation of individual components-additives to existing foaming agents that improve their quality (additive of polymers to increase the stability of the foam);

Improving the design of foam generators (high-expansion foam obtained without forced air supply or filled with an inert gas);

Improvement of tactics for extinguishing fires with the use of foam.

Foam fire extinguishing - extinguishing a fire using foam.

Foams are widely used to extinguish fires at industrial enterprises, warehouses, oil storage facilities, transport, etc. Foams are dispersed systems consisting of gas bubbles surrounded by liquid films and characterized by relative aggregate and thermodynamic instability. If gas bubbles have a spherical shape, and their total volume is comparable to the volume of liquid, then such systems are called gas emulsions. To obtain air-mechanical foam, special equipment and aqueous solutions of foam concentrates are required.

Advantages of foam as an extinguishing agent:

significant reduction in water consumption;

Possibility of extinguishing fires of large areas;

Possibility of volumetric quenching;

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 able to spread over the surface of the burning material.

The most important structural characteristic of foam is its multiplicity, which is understood as the ratio of the foam volume to the volume of its liquid phase. Air-mechanical foam is divided into:

low-fold (multiplicity up to 20);

medium multiple (20 - 100);

high-fold (above 100).

Aircraft carrier foam extinguishing system.

The most widely used foam is medium-expansion (in Russia), less often - low-expansion. High-expansion foam finds limited use in fire extinguishing, mainly in volumetric extinguishing.

The scope of air-mechanical foam should be limited only to flammable oil products with a low flash point. The share of diesel fuel in the total balance of petroleum products is constantly growing. Replacing foam systems with agitation systems for diesel fuel tanks in large warehouses of industrial, energy and transport enterprises can provide a significant technical and economic effect. Widespread adoption of agitation extinguishing systems can reduce the amount of foam concentrate required, provide a second independent fire extinguishing system in a mixed tank farm, and use an agitation system to cool the liquid surface/fire-heated tank.

Air-mechanical foams can be used to extinguish both liquid and solid combustible materials.

When extinguishing flammable liquids, the greatest effect is achieved by applying the maximum amount of foam in the shortest possible time.

It is necessary to apply a foam jet to a burning surface after high-quality foam begins to come out of the barrel.

A jet of foam should be applied to the edge of the fire area and, moving it to the center, cover the entire surface of the burning liquid with foam. Do not drive the barrel over a burning surface: this contributes to the destruction of the foam.

Foam can be applied to the bulkheads above the fire: spreading from the bulkheads, it will evenly cover the burning surface.

To extinguish burning vertical surfaces, foam should be applied to the upper part of the surface.

In cold weather, it is not necessary to use foam for a long time to prevent malfunctions in the foam barrel due to freezing of the foam concentrate.

The suction of hot smoke into the foam generator sharply reduces the expansion and stability of the foam, so foam generators should be used on the windward side. The simultaneous use of foam and water to extinguish a fire is impractical, since the supplied water will destroy the foam. Air-mechanical foam of medium and high expansion can also be used as a volumetric fire extinguishing agent.

Figure 1 Foam Application

Foam concentrates

Depending on the chemical composition (surfactant base), foaming agents are divided into:

Synthetic hydrocarbons

Synthetic fluoride.

According to the type of impact on the fire source, there are:

surface - deluge. Protection of the entire settlement area; installations for the protection of tanks with flammable liquids;

Local-surface: sprinkler - to protect individual devices, individual sections of the premises; deluge - to protect individual objects, apparatus, transformers, etc.;

general volume - designed to fill protected volumes;

· local-volumetric - for filling individual volumes of technological apparatuses, small built-in storage facilities and others;

· combined - the schemes of installations of local-surface and local-volume extinguishing are connected for the simultaneous supply of foam into the volume or along the surface of technological apparatuses and to the surface around them.

Types of foam concentrates

1. Synthetic hydrocarbon foaming agents

This type has in its composition mainly surface-active hydrocarbon substances, which have a special synthetic nature. They are also divided into foam concentrates of the target, as well as general purpose type. Foam concentrates with a specific purpose are used exclusively for extinguishing fires that correspond to the technical parameters for the use of this type of foam concentrate. General-purpose foam concentrates are used exclusively for extinguishing fires in which liquid (including oil products) and solid types of substances ignite.

2. Protein frothers

Foaming agents of this type consist mainly of active surface substances obtained by hydrolysis of various protein compounds. These compounds are used to eliminate burning oil products, oil, and other combustible liquid substances.

3. Foaming agents fluorine-containing synthetic

These blowing agents consist mainly of fluorine and its derivatives. Compositions of this kind are used to eliminate burning combustible liquid substances.

4. Synthetic film-forming foaming agents

When extinguishing with this composition, a special film is formed on the surface of ignited surfaces, which prevents combustion. This composition is based on fluorocarbon substances. Compared to hydrocarbons, these foam concentrates are much better able to extinguish fires of almost any complexity level that have arisen on any surfaces.

5. Protein fluoride foaming agents

These foaming agents consist mainly of fluorine-containing additives, due to which the foaming process occurs. Protein fluorine-containing foam concentrates have a high ability to extinguish fires of almost any type of material. Foam concentrates of this type are actively used in the elimination of fires that occur at extremely fire hazardous facilities.

Foam concentrate dispensers

Various devices are used to mix the foaming agent into the water:

Devices based on the principle of the Venturi tube. These are the simplest dispensers. Their advantage lies in the simplicity of the device, low cost. The main disadvantages of such a system are large losses in the pressure pipeline, the impossibility of obtaining concentrations below 3%, the impossibility of obtaining the exact concentration of the solution.

Dosing tanks - devices that combine a container for storing a foam concentrate and a dosing device, operate regardless of the pressure in the system. Disadvantages - it is impossible to control visually or with the help of sensors the remaining foam concentrate, bulkiness, high operating costs.

Figure 2. Portable Dispenser Driven by Hydraulic Motor

Dosing pumps driven by a hydraulic motor (Fig. 2) are the most modern system and easy to operate system, does not require an external power source, operates in a wide range of flow rates and pressures. Simple and reliable in operation.

Disadvantages - the dosing pump is located in close proximity to the supply pipeline - the presence of a suction pipeline for the supply of a foaming agent.

Types of air-mechanical foams

Air-mechanical foam is formed as a result of intensive mechanical mixing of an aqueous solution of a foaming agent with air.

Foaming agents PO-1 and PO-6 are used to produce foam.

Foaming agent PO-l is a neutralized kerosene contact containing at least 45% sulfonic acids. To obtain the required expansion and stability of the foam, 4.5% glue and 10% alcohol or ethylene glycol are added to it.

Foaming agent PO-6 is a product of alkaline hydrolysis of technical blood of animals. To give foam stability, 1% ferrous sulfate is added to it. To prevent rotting of the foaming agent during long-term storage, 4% sodium fluoride is added to it.

Foam concentrates must meet the requirements of GOST 6948--54 and GOST 9603--61.

Air-mechanical foam consists of bubbles, the shell of which is formed from a foaming agent solution. The bubbles contain (depending on the foaming agent) up to 90% air, 9.5% water and up to 0.5% foaming agent. The specific gravity of the foam is from 0.11 to 0.17.

It turns out air-mechanical foam with the help of special devices (mixers and air-foam barrels). The durability of the foam based on the PO-1 foam concentrate is 30 minutes, and on the basis of the PO-6 foam concentrate it is at least 60 minutes. VNIIPO has developed a formula for foaming agent PO-8 to obtain an air-mechanical foam of increased resistance, which is used to extinguish oil products and polar liquids (alcohol, acetone, etc.).

Air-mechanical foam according to the output ratio is divided into normal and high expansion foam.

Foam of normal expansion is considered when from 1 liter of foam concentrate PO-1 and 25 liters of water form from 200 to 300 liters of foam, from 1 liter of foam concentrate PO-6 and 25 liters of water - from 125 to 175 liters.

Foam from foam concentrate PO-6 is more stable than from foam concentrate PO-1. To obtain foam of normal expansion, aqueous solutions of foaming agents PO-1 (3-4% by volume) and PO-6 (4-6% by volume) are used.

Foaming agent PO-1 is considered suitable if the foam output ratio is at least 10, its durability is at least 30 minutes, and foam concentrate PO-6, if the foam output ratio is at least 5, its durability is at least 60 minutes.

Normal expansion foam holds well on vertical surfaces, so it can be used to protect materials and structures from fire when exposed to radiant heat.

It is advisable to use air-mechanical foam of normal expansion to extinguish oil products with a flash point of 45 ° C and above, located in containers, and oil products with a flash point of 45 ° C and below (with the exception of aviation gasoline), spilled in a thin layer over a hard cover or on the surface of water .

It can also be used to extinguish oil products with a flash point of 45 ° C and below (with the exception of gasoline) in containers. But at the same time, it must be remembered that to extinguish oil products with a flash point of 28 ° C and below, on an area of ​​\u200b\u200bnot more than 100 m2, air-mechanical foam of normal expansion based on foam concentrate PO-1 can be used, and on an area of ​​\u200b\u200bnot more than 400-500 m2 - - based on foaming agent PO-6. The distance from the upper edge of the side of the tank to the liquid surface should be no more than 2 m. This condition should also be observed when extinguishing oil products with a flash point of 28 to 45 ° C.

Foam concentrates are ineffective in extinguishing fires of polar liquids (alcohol, ether, acetone).

To extinguish oil products (gasoline, kerosene, crude oil, fuel oil), along with foaming agent PO-1, NB wetting agent is used.

VNIIPO has developed a method for extinguishing oil products in containers by supplying air-mechanical foam through a layer of fuel. In this case, the fire can be extinguished at any level of fuel in the tanks.

High expansion foam based on PO-1 or PO-6 foam concentrates is produced by a special generator operating on the principle of enhanced air suction. It can be used for localization of fires of solid substances, fiery combustion in rooms. Foam gives high fire-extinguishing efficiency when extinguishing oil products.

When it extinguishes fiery combustion in the premises, smoke and combustion products are displaced, the combustion centers are localized, and favorable conditions are created for the complete cessation of combustion.

As the rooms are filled with high-expansion foam, the temperature in them quickly decreases as a result of the displacement of hot gases, the cessation of combustion and the partial cooling of structures. The temperature in a burning room, as practice shows, immediately after the foam is supplied to it, it can drop from 1000 ° C or more to 65--50 ° C.

After filling the room with foam, the temperature in it may rise again, since the heated floor structures do not have time to cool due to the short-term action of the foam.

High-expansion foam can only extinguish a flame due to the presence of a large amount of air in it and the limited time of its supply. The centers of smoldering of solids remain unextinguished.

Under the influence of the heat released during smoldering, the foam quickly collapses.

The complete elimination of smoldering centers depends on the intensity and time of foam supply and on how quickly it penetrates to the combustion sites.

In practice, high expansion foam is not thermally conductive. Fluctuations in ambient temperature from -30 to +30°C do not have a significant effect on the quality of the foam. At low temperatures (below -15°C), the foam's resistance is somewhat reduced, although a stable crust forms on its surface. High temperature accelerates the destruction of the foam.

Foam does not have a harmful effect on most materials and equipment, does not create additional load on structures due to its low volumetric weight.

The foaming solution is a good wetting agent and therefore freely penetrates into materials, including fibrous ones.

When using air-mechanical foam, the work of firefighters during fire extinguishing is greatly facilitated. Therefore, it is widely used in fire fighting, it is the main fire extinguishing agent.

When extinguishing oil products, it is necessary to use the calculated amount of both chemical and air-mechanical foam. Instructions for their calculation are set out in Appendix 4 of the “Fire Safety Rules for River Transport of the Ministry of the River Fleet of the RSFSR”.

Carbon dioxide (technical name for carbon dioxide) CO2 is a colorless gas with a barely perceptible odor, does not burn and does not support combustion, and does not conduct electricity. The extinguishing concentration of carbon dioxide vapor in the air should be 22.4% (by volume). At 0°C and a pressure of 36 kgf/cm2, it easily liquefies, passing from a gaseous state to a liquid one.

The heat of vaporization of liquid carbon dioxide is 47.7 cal/kg. With the rapid evaporation of liquid carbon dioxide, solid (snow-like) carbon dioxide is formed. The specific gravity of such carbon dioxide at a temperature of -79 ° C is 1.53. Carbon dioxide or carbon dioxide snow directed into the fire zone reduces the oxygen concentration in it to such a value that combustion is impossible, and also cools the burning substance and the environment, as a result of which combustion stops.

Carbon dioxide is used to extinguish fires in enclosed spaces (under conditions of limited air exchange) and in a relatively small area directly in the air. It is used to extinguish fires in energized electrical installations.

When extinguishing fires in enclosed spaces, 0.495 kg / m3 of carbon dioxide is consumed, and in the most fire hazardous premises - 0.594 / kg / m3.

Flame combustion in the cargo hold of a vessel when carbon dioxide is used stops when the percentage of oxygen in it decreases to 14%. The smoldering, however, continues. To stop it, the oxygen content in the hold must be increased to 5%. Carbon dioxide must be fed into the hold until the smoldering completely stops, and it can last from several hours to one or two days.

Carbon dioxide as an independent extinguishing agent in stationary fire-fighting installations on river transport is rarely used. It is replaced by more effective means - halohydrocarbons: ethyl bromide, methylene bromide, tetrafluorodibromoethane, which are included in the composition of such fire extinguishing mixtures as "3.5", SZhB and one-component freon-114V2.

fire extinguishing foam extinguishing

The main methods of extinguishing fires

Consider the main methods of extinguishing fires and the extinguishing agents used in this case.

To extinguish a fire, the following means are used: dilution of air with non-combustible gases to such oxygen concentrations at which combustion stops; cooling the combustion chamber below a certain temperature (combustion temperature); mechanical breakdown of the flame by a jet of liquid or gas; a decrease in the rate of a chemical reaction occurring in a flame; creation of fire barrier conditions under which the flame spreads through narrow channels.

Fire retardants are substances that, when introduced into the combustion zone, stop combustion. The main extinguishing agents and materials are water and water vapor, chemical and air-mechanical foams, aqueous solutions of salts, non-combustible gases, halocarbon fire extinguishing compositions and dry fire extinguishing powders.

Chemical and air-mechanical foams are used to extinguish solid and liquid substances that do not interact with water. One of the main characteristics of these foams is their multiplicity, i.e. the ratio of the volume of the foam to the volume of its liquid phase.

Fire fighting equipment is divided into primary, stationary and mobile (fire trucks).

Primary means are used to eliminate small fires and sunbathing. They are usually used before the arrival of the fire brigade. Primary means include mobile and manual fire extinguishers, portable fire extinguishing installations, internal fire hydrants, sandboxes, asbestos blankets, fire shields with a set of equipment, etc.

Fire extinguishers are marked with letters characterizing the type of fire extinguisher by category, and a number indicating its volume in liters.

Air-foam fire extinguishers are marked as ORP (for example, manual ORP-5 and ORP-10). They are used to extinguish fires of flammable liquids, combustible liquids, most solid materials (except metals). They cannot be used to extinguish electrical installations that are energized.

Stationary installations are designed to extinguish fires in the initial stage of their occurrence. They start automatically or by remote control. These installations are filled with the following fire extinguishing agents: water, foam, non-flammable gases, powder compositions or steam.

Automatic water fire extinguishing installations include sprinkler and deluge installations. The holes through which water enters the room in case of fire are sealed with fusible alloys. These alloys melt at a certain temperature and open access to sprayed water.

Each head irrigates the room and the equipment located in it with an area of ​​up to 9 m2.

In cases where it is advisable to supply water to the entire area of ​​​​the room in which the fire broke out, drenchers are used, which are also a pipe system filled with water, equipped with spray heads-drenchers. In them, unlike sprinkler heads, the water outlets (diameter 8, 10 and 12.7 mm) are constantly open. Sprinkler heads are actuated by opening a group acting valve which is normally closed. It opens automatically or manually (an alarm is given). Each sprinkler head irrigates 9-12 m2 of floor area.

The system works as follows.

1. The fire sensor (detector) reacts to the appearance of smoke (smoke detector),

2. to increase the air temperature in the room (heat detector),

3. to the radiation of an open flame (light detector), etc.

4. and gives a signal to turn on the system for supplying fire extinguishing agents that are supplied to the source of fire.

Fire sensors (detectors) can be either manual (fire buttons installed in the corridors of premises and on landings) or automatic. The latter, as mentioned above, are divided into thermal, smoke and light. Smoke detectors use two main methods for detecting smoke - photoelectric and radioisotope. So, smoke photovoltaic (IDF-1M) and semiconductor (DIP-1) operate on the principle of dispersion of thermal radiation by smoke particles. Radioisotope smoke detectors (RID-1) are based on the effect of weakening the ionization of the interelectrode gap by charged particles that are part of the smoke. One smoke detector is installed on 65m2 of protected area. There are combined detectors (KI) that react to heat and smoke.

The signal from fire detectors is transmitted to fire stations, the most common of which are TLO-10/100 (alarm beam optical) and "Komar - 12 AM signal" (small capacity concentrator). Fire trucks (tank trucks and special ones) are used as mobile fire extinguishing equipment.

Foam storage

Upon receipt of a concentrated foaming agent, it is necessary to make sure that there is a document certifying its quality and quantity.

After that, a tank filling scheme is prepared and the pump for pumping concentrated foam concentrate is turned on. At the end of the pumping of the foaming agent, the original recirculation scheme is restored.

Before refueling AUPP, it is necessary to check the quality of the foam concentrate or its ready-made solution according to the method given in the work “Procedure for the use, transportation, storage and quality control of foam concentrates for extinguishing fires. (Instruction)". Moscow: VNIIPO MVD USSR, 1989). Analysis of the foaming agent solution is carried out in the laboratory of the power company.

In the future, the quality of the foam concentrate or its aqueous solution in the AUPP should be checked once every six months.

If the ratio of the foam obtained in the laboratory is less than 5 or its stability is less than 3 minutes, replace the foaming agent and its aqueous solution.

An unsuitable foaming agent solution according to the appropriate scheme can be supplied through steam-mechanical fuel oil nozzles to the furnaces of operating boilers for combustion, or disposed of in another way that does not contradict environmental requirements.

After the activation of the AUPP, further use of the foaming agent or its aqueous solution is allowed, depending on the amount of residue and its quality. It is not allowed to mix the remaining foaming agent or its aqueous solution with other brands of foaming agent. Before filling the container with a new foaming agent, it is necessary to check its quality if it has not been checked for more than 3 months.

Storage of foam concentrates in reinforced concrete tanks is not recommended.

Stocks of clean water can be stored in concrete, reinforced concrete, metal and other tanks.

Reservoirs for storing stocks of an aqueous solution of foam concentrates or water must be equipped with automatic level gauges with readings displayed on the control panel.

Checking the level of an aqueous solution of a foaming agent or water should be carried out daily with registration in the "Journal of maintenance and repair of the fire extinguishing installation".

If the level of the foaming agent water solution or water decreases due to evaporation, water should be added. If there are leaks, locate the damage to the tank and repair the leaks, then check the quality of the remaining foam concentrate.

Ready water solution of foaming agents in tanks and in the pipeline network must be mixed at least once every three months.

Water for the preparation of the solution and the solution should not contain mechanical impurities that can clog pipelines, throttle washers and steam generator grids. The water for the preparation of the spread must meet the requirements for drinking water.

To prevent rotting and flowering of water, it is recommended to disinfect it with bleach at the rate of 100 g of lime per 1 m 3 of water. Ready water solution of the foaming agent is not subject to disinfection.

Replacing the water in the tank should be done annually. When replacing water or a ready-made aqueous solution of a foaming agent, the bottom and inner walls of the tank are cleaned of dirt and build-up, the damaged color is restored or completely renewed.

Conclusion

In my work, it is described in detail about the air-mechanical foam. The material allows you to compare and evaluate different fire extinguishing agents. And the results of this comparison tell us that such foam is far from the best fire extinguishing agent.

The low destructive effect and overall higher efficiency make it more effective than water in most cases. However, on the other hand, it extinguishes thermal energy worse.

In my work, it is indicated that one of the best OM is a gas that, when mixed in air, does not give the desired composition to continue burning. But in different conditions, its use is impossible, and air-mechanical foam becomes more effective.

The final conclusion can be said that there are no better or worse OVs, there is a correct and incorrect application of them. And our business, as specialists, is to use the most suitable substances for a given situation or to combine them correctly.

List of sources

1. Wikipedia

2. Portal 0-1.ru

3. Great Encyclopedia of Oil and Gas

4. Internet club "Kubrik"

5. GOST 6948--54

6. GOST 9603--61

7. Russian encyclopedia of labor protection: In 3 volumes - 2nd ed., Revised. and additional -- M.: Publishing house of NTs ENAS, 2007.

8. “The procedure for the use, transportation, storage and quality control of foam concentrates for extinguishing fires. (Instruction)". Moscow: VNIIPO MVD USSR, 1989).

9. Operating instructions for fire extinguishing installations using air-mechanical foam (RD 34.49.502-96)

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General information about tanks and storage parks for flammable liquids and combustible liquids and fires in them. Safety requirements for extinguishing oil products in ground tanks. Normative intensity of low-expansion foam supply for extinguishing oil fires.

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 flammable vapors and gases from entering the combustion zone, 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. 3.23).

FOAM FIRE GUNS

For low expansion foam

For medium expansion foam

Combined for low and medium expansion foam

Rice. 3.23. Classification of foam fire nozzles

Foam shaft - a device installed at the end of the pressure line for the formation of jets of air-mechanical foam of various multiplicity from an aqueous solution of a foaming agent.

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

The trunk of the SVPE (Fig. 3.24) consists of a body 8 , on one side of which a pin connection head is screwed 7 for connecting the barrel to a hose pressure line of the corresponding diameter, and on the other hand, a 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 of at least 600 mm Hg. Art. (0.08 MPa).

Rice. 3.24. 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 trunk (Fig. 3.25) is as follows. 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. 3.25. Barrel air-foam SVP:

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

The principle of foam formation in the shaft of the SVP 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 barrel or other container. Technical characteristics of fire nozzles for obtaining low expansion foam are presented in Table. 3.10.

Table 3.10

Medium expansion foam generators are used to obtain medium expansion air-mechanical foam from an aqueous solution of a foaming agent and supply it to the fire site.

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. 3.11.

Table 3.11

Foam generators GPS-200 and GPS-600 are identical in design and differ only in the geometrical dimensions of the atomizer and housing. The generator is a portable water-jet ejector apparatus and consists of the following main parts (Fig. 3.26): generator body 1 with guiding device, mesh package 2 , centrifugal atomizer 3 , nozzle 4 and collector 5 . The atomizer housing 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). Swirl type atomizer 3 has six windows located at an angle of 12 °, which causes the flow of the working fluid to swirl and provides an atomized 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. 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.

As foam fire nozzles of the combined type, we consider the installation of combined fire extinguishing (UKTP) "Purga", which can be manual, stationary and mobile. They are designed to produce low and medium expansion air-mechanical foam. Technical characteristics of UKTP of various designs are presented in Table. 3.12. In addition, a range diagram and an irrigation map (Fig. 3.27) have been developed for these trunks, which makes it possible to more clearly assess their tactical capabilities in extinguishing fires.

Table 3.12