To obtain medium expansion foam

Combined to produce low and medium expansion foam

Rice. 3.23. Classification of foam fire nozzles

A foam barrel is a device installed at the end of a pressure line to form jets of air-mechanical foam of various expansion rates 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, differing only in size, as well as an ejector device designed to suck the foaming agent from the container.

The SVPE barrel (Fig. 3.24) consists of a body 8 , on one side of which a pin connection head is screwed 7 to connect the barrel to a hose pressure line of the corresponding diameter, and on the other hand, a pipe is attached with screws 5 , made of aluminum alloy and designed to form air-mechanical foam and direct it to the source of the fire. There are three chambers in the barrel body: receiving 6 , vacuum 3 and day off 4 . There is a nipple on the vacuum chamber 2 with a diameter of 16 mm for connecting a hose 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 ejecting device 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 barrel (Fig. 3.25) is as follows. Foaming solution passing through the hole 2 in the barrel body 1 , creates in a conical chamber 3 vacuum, due to which air is sucked through eight holes evenly spaced in the guide pipe 4 trunk The air entering the pipe is intensively mixed with the foam-forming solution and forms a stream of air-mechanical foam at the exit from the barrel.

Rice. 3.25. Air-foam SVP barrel:

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

The principle of foam formation in the SVPE barrel differs from SVP in that it is not the foam-forming solution that enters the receiving chamber, but water, which, passing through the central hole, creates a vacuum in the vacuum chamber. A foam agent is sucked into the vacuum chamber through a nipple through a hose from a backpack barrel or other container. Technical characteristics of fire trunks for producing low expansion foam are presented in table. 3.10.

Table 3.10

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

Depending on the foam productivity, 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 geometric dimensions of the sprayer and housing. The generator is a portable water-jet ejector apparatus and consists of the following main parts (Fig. 3.26): generator housing 1 with guide device, mesh package 2 , centrifugal sprayer 3 , nozzle 4 and collector 5 . The atomizer body, in which the atomizer is mounted, is attached to the generator manifold using three stands 3 and coupling head GM-70. Mesh Pack 2 It is a ring covered along the end planes with a metal mesh (mesh size 0.8 mm). Vortex type atomizer 3 has six windows located at an angle of 12 °, which causes swirling of the flow of working fluid and ensures a sprayed jet at the exit. Nozzles 4 designed to form a foam stream after a package of meshes into a compact stream and increase the flight range of the foam. Air-mechanical foam is obtained by mixing three components in a generator in a certain proportion: water, foaming agent and air. A flow of foaming agent solution is fed under pressure into the sprayer. As a result of ejection, when a sprayed jet enters the collector, air is sucked in and mixed with the solution. A mixture of drops of foaming solution and air falls on the mesh package. On grids, deformed drops form a system of stretched films, which, enclosed in limited volumes, form first elementary (individual bubbles) and then mass foam. The energy of the newly arriving droplets and air forces the mass of foam out of the foam generator.

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

Table 3.12

Introduction

Foaming agents

Types of foaming agents

Foam dispensers

Foam concentrate storage

Conclusion

List of sources

Introduction

The topic of my work: “Features of using air-mechanical foam for extinguishing fires.”

My work should tell and explain what air-mechanical foam is, how and where it is used, as well as 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, all types of air-mechanical foams are actually used: low, medium and high expansion foam. In this case, foam concentrates are used in accordance with their purpose, chemical composition, and method of supply.

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

· creation of new modern foam concentrates;

· creation of individual components-additives to existing foaming agents that improve their quality (adding polymers to increase foam durability);

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

· improving tactical techniques for extinguishing fires using foam.

Foam fire extinguishing is extinguishing a fire using foam.

Foams are widely used to extinguish fires in 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 the gas bubbles have a spherical shape, and their total volume is comparable to the volume of the liquid, then such systems are called gas emulsions. To obtain air-mechanical foam, special equipment and aqueous solutions of foaming agents are required.

Advantages of foam as an extinguishing agent:

· significant reduction in water consumption;

· the ability to extinguish large area fires;

· Possibility of volumetric extinguishing;

· possibility of sub-layer extinguishing of oil products in tanks;

· increased (compared to water) wetting ability.

· when extinguishing with foam, it is not necessary to simultaneously cover the entire combustion surface, since the foam can spread over the surface of the burning material.

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

low-multiplicity (multiplicity up to 20);

medium multiple (20 -- 100);

high-fold (above 100).

Foam extinguishing system on an aircraft carrier.

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

It is advisable to limit the scope of application of air-mechanical foam only to flammable petroleum 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 stirring extinguishing 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 required foam concentrate reserves, provide a second independent fire extinguishing system in a mixed tank farm, and also use the agitation system to cool the surface layer of the liquid / in a fire-heated tank.

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

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

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

A stream 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. You should not move the barrel over a burning surface: this will destroy 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 top of the surface.

In cold weather, there is no need to use foam for a long time to prevent malfunction of the foam barrel due to freezing of the foam concentrate.

The suction of hot smoke into the foam generator sharply reduces the expansion rate and durability 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. Application of foam

Foaming agents

Depending on the chemical composition (surface-active base), foaming agents are divided into:

· synthetic hydrocarbons;

· synthetic fluorine-containing.

Based on the type of impact on the fire source, the following are distinguished:

· surface - deluge. Protection of the entire design area; installations for protecting tanks with flammable liquids;

· local-surface: sprinkler - to protect individual devices, individual areas of premises; deluge - for the protection of individual objects, devices, transformers, etc.;

· general-volume - designed to fill protected volumes;

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

· combined - circuits of local-surface and local-volumetric extinguishing installations are connected for simultaneous supply of foam into the volume or along the surface of technological devices and onto the surface around them.

Types of foaming agents

1. Synthetic hydrocarbon foaming agents

This type consists mainly of surfactant hydrocarbon substances of a special synthetic nature. They are also divided into foam concentrates of a targeted type, as well as general purpose ones. Foaming agents that have a specific purpose are used exclusively for extinguishing fires that comply with the technical parameters for using this type of foaming agent. General purpose foam concentrates are used exclusively to extinguish fires in which liquid (including petroleum products) and also solid types of substances ignite.

2. Protein foaming agents

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

3. Fluorine-containing synthetic foaming agents

These foaming agents consist mainly of fluorine, as well as its derivatives. Compositions of this kind are used to eliminate burning flammable liquid substances.

4. Synthetic film-forming foaming agents

When extinguishing with this composition, a special film is formed on the surface of the ignited surfaces, which prevents combustion. This composition is based on fluorocarbon substances. Compared to hydrocarbon foams, these foaming agents are much better able to extinguish fires of almost any level of complexity that occur on any surface.

5. Protein fluorinated foaming agents

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

Foam dispensers

Various devices are used to mix foaming agent into water:

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

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

Figure 2. Portable dispenser driven by a hydraulic motor

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

Disadvantages - the metering pump is located in close proximity to the supply pipeline - the presence of a suction pipeline for supplying the foam concentrate.

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.

To obtain foam, foam concentrates PO-1 and PO-6 are used.

Foaming agent PO-l is a neutralized kerosene contact containing at least 45% sulfonic acids. To obtain the required expansion and durability 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 industrial animal blood. To make the foam stable, 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) air up to 90%, water 9.5% and foaming agent up to 0.5%. The specific gravity of the foam is from 0.11 to 0.17.

Air-mechanical foam is obtained using special devices (mixers and air-foam barrels). The durability of foam based on foaming agent PO-1 is 30 minutes, and that based on foaming agent PO-6 is at least 60 minutes. VNIIPO has developed a foam concentrate formulation PO-8 to produce air-mechanical foam of increased resistance, which is used when extinguishing petroleum products and polar liquids (alcohol, acetone, etc.).

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

Foam of normal expansion is considered in the case when from 1 liter of foaming agent PO-1 and 25 liters of water, from 200 to 300 liters of foam are formed, from 1 liter of foaming agent PO-6 and 25 liters of water - from 125 to 175 liters.

Foam from foaming agent PO-6 is more stable than foaming agent 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 and its durability is at least 30 minutes, and foaming agent PO-6 is considered suitable if the foam output ratio is at least 5 and its durability is at least 60 minutes.

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

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

It can also be used for extinguishing petroleum products with a flash point of 45 ° C and below (except for gasoline) in containers. But at the same time, we must remember that to extinguish oil products with a flash point of 28 ° C and below on an area of ​​no more than 100 m2, you can use air-mechanical foam of normal expansion based on the PO-1 foaming agent, and on an area of ​​​​no more than 400-500 m2 - - based on foaming agent PO-6. The distance from the upper edge of the side of the container 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.

Foaming agents are ineffective when extinguishing fires of polar liquids (alcohol, ether, acetone).

To extinguish petroleum products (gasoline, kerosene, crude oil, fuel oil), along with the PO-1 foaming agent, the 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 containers.

High expansion foam based on foam concentrates PO-1 or PO-6 is produced by a special generator operating on the principle of enhanced air suction. It can be used to localize fires of solid substances and flaming combustion in premises. Foam provides high fire extinguishing efficiency when extinguishing petroleum products.

When it extinguishes a flaming fire in the premises, smoke and combustion products are displaced, combustion sources are localized, and favorable conditions are created for the complete cessation of combustion.

As the premises 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 introducing foam into 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 effect of the foam.

High expansion foam can only extinguish a fire due to the presence of a large amount of air in it and the limited time of its supply. The smoldering areas of solid substances remain unextinguished.

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

Complete elimination of smoldering sites depends on the intensity and time of foam supply and on how quickly it penetrates to the burning 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 durability of the foam decreases somewhat, although a stable crust forms on its surface. High temperature accelerates the destruction of foam.

Foam does not have a harmful effect on most materials and equipment, and does not create additional load on structures due to its insignificant 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 when extinguishing a fire is greatly facilitated. Therefore, it is widely used in extinguishing fires; 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 on River Transport of the Ministry of River Fleet of the RSFSR”.

Carbon dioxide (technical name for carbon dioxide) CO2 is a colorless gas with a barely noticeable odor, does not burn and does not support combustion, and does not conduct current. The fire 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 evaporation 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 level 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 (in conditions of limited air exchange) and in a relatively small area directly in the air. It is used to extinguish fires in live electrical installations.

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

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

Carbon dioxide is rarely used as an independent fire extinguishing agent in stationary fire-fighting installations on river transport. It is being 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”, SRC and one-component freon-114B2.

fire extinguishing fire extinguishing foam

Basic methods of extinguishing fires

Let's look at the main methods of extinguishing fires and the extinguishing agents used.

To extinguish a fire, the following means are used: diluting the air with non-flammable gases to oxygen concentrations at which combustion stops; cooling the combustion site below a certain temperature (combustion temperature); mechanical flame arrest by a jet of liquid or gas; reducing the rate of chemical reaction occurring in the flame; creating fire barrier conditions under which the flame spreads through narrow channels.

Fire extinguishing agents are substances that, when introduced into the combustion zone, stop combustion. The main fire extinguishing substances and materials are water and water vapor, chemical and air-mechanical foams, aqueous solutions of salts, non-flammable gases, halocarbon fire extinguishing compounds 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 expansion ratio, i.e. the ratio of the volume of the foam to the volume of its liquid phase.

Fire extinguishing means are divided into primary, stationary and mobile (fire trucks).

Primary means are used to eliminate small fires and tanning. They are usually used before the fire brigade arrives. Primary means include mobile and hand-held fire extinguishers, portable fire extinguishing installations, internal fire hydrants, sand boxes, 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 labeled as ORP (for example, manual ORP-5 and ORP-10). They are used to extinguish fires of flammable liquids, gases, and most solid materials (except metals). They cannot be used to extinguish live electrical installations.

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

Automatic water fire extinguishing systems include sprinkler and deluge systems. The holes through which water enters the room during a fire are sealed with low-melting alloys. These alloys melt at a certain temperature and allow water to be sprayed.

Each head irrigates a room and 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 occurred, deluges are used, which are also a pipe system filled with water, equipped with deluge spray heads. In them, unlike sprinkler heads, the water outlets (8, 10 and 12.7 mm in diameter) are constantly open. Sprinkler heads are activated by opening a group valve that is normally closed. It opens automatically or manually (an alarm is generated). 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. for radiation from an open flame (light detector), etc.

4. and sends a signal to turn on the fire extinguishing agent supply system, which is supplied to the source of fire.

Fire sensors (detectors) can be either manual (fire buttons installed in the corridors of premises and on staircases) or automatic. The latter, as mentioned above, are divided into thermal, smoke and light. Smoke detectors use two main methods of detecting smoke - photoelectric and radioisotope. Thus, smoke photoelectric (IDF-1M) and semiconductor (DIP-1) operate on the principle of dissipation 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 65 m2 of protected area. There are combined detectors (CDs) that respond to heat and smoke.

The signal from fire detectors is transmitted to fire stations, the most common of which are TLO-10/100 (beam optical alarm) and “Komar - signal 12 AM” (low-capacity concentrator). Firefighting vehicles (tankers and special ones) are used as mobile fire extinguishing equipment.

Foam concentrate storage

When you receive a concentrated foaming agent, you must ensure that you have a document certifying its quality and quantity.

After this, a scheme for filling the containers is prepared and the pump is turned on to pump the concentrated foaming agent. Upon completion of pumping of the foam concentrate, the original recirculation scheme is restored.

Before refueling the AUPP, it is necessary to check the quality of the foam concentrate or its finished solution according to the method given in the work “Procedure for use, transportation, storage and quality control of foam concentrates for extinguishing fires. (Instructions)". M.: VNIIPO Ministry of Internal Affairs of the USSR, 1989). The analysis of the foam concentrate solution is carried out in the laboratory of the energy company.

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

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

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

After the automatic control device has been activated, further use of the foaming agent or its aqueous solution is permitted depending on the amount of residue and its quality. The remaining foaming agent or its aqueous solution must not be mixed 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.

Storing foam concentrates in reinforced concrete tanks is not recommended.

Clean water supplies can be stored in concrete, reinforced concrete, metal and other tanks.

Tanks for storing reserves of an aqueous solution of foaming agents or water must be equipped with automatic level meters with readings displayed on the control panel.

Checking the level of the aqueous solution of the foaming agent or water must be carried out daily and recorded in the “Logbook for the maintenance and repair of the fire extinguishing installation.”

If the level of the foaming agent aqueous 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.

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

The water for preparing the solution and the solution must not contain mechanical impurities that can clog pipelines, throttle washers and steam generator screens. The water for preparing the spread must meet the requirements for drinking water.

To prevent decay and blooming of water, it is recommended to disinfect it with bleach at the rate of 100 g of lime per 1 m 3 of water. The prepared aqueous solution of the foaming agent cannot be disinfected.

The water in the tank must be replaced 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 growths, the damaged color is restored or completely renewed.

Conclusion

My work talks in detail about 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.

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

My work indicates that one of the best OMs is a gas that, when mixed in air, does not provide the required composition to continue combustion. 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 agents, there are correct and incorrect uses. And our job, 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 "Kubrick"

5. GOST 6948--54

6. GOST 9603--61

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

8. “The procedure for using, transporting, storing and checking the quality of foaming agents for extinguishing fires. (Instructions)". M.: VNIIPO Ministry of Internal Affairs of the USSR, 1989).

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

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RUSSIANJOINT STOCKSOCIETYENERGY
ANDELECTRIFICATION « UESRUSSIA»

DEPARTMENTSCIENCEANDTECHNIQUES

INSTRUCTIONS
BY OPERATIONINSTALLATIONS
FIRE FIGHTING WITHAPPLICATION
AIR - MECHANICALFOAM

RD 34.49.502-96

ORGRES

Moscow 1996

DevelopedJoint-stock company “Company for adjustment, improvement of technology and operation of power plants and networks “ORGRES”.

PerformersYES. ZAZAMLOV, A.N. IVANOV, A.S. KOZLOV, V.M. OLD PEOPLE

Agreedwith the Department of the General Inspectorate for the Operation of Power Plants and Networks of RAO UES of Russia 04/16/96

Chief engineer A.D. Shcherbakov

ApprovedDepartment of Science and Technology RAO "UES of Russia" 04/17/96

Chief A.P. BERSENEV

Expiration 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 storage conditions for foam concentrates and their aqueous solutions are described. The technical requirements for the operation of equipment for fire extinguishing installations in general and their individual elements are outlined.

The procedure for organizing testing and acceptance into operation of newly installed fire extinguishing installations and the regulations for conducting inspections of the technical condition of equipment, equipment and instruments of the fire extinguishing installation and the timing of the audit of the entire installation have been determined.

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

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

The forms of reports for flushing and hydraulic testing of pressure and distribution pipelines of fire extinguishing installations, the form of a logbook for the maintenance and repair of fire extinguishing installations, and the form of a report for conducting fire tests are given.

With the publication of this Instruction, the “Instructions 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 . Foaming agents and fire fighting equipment are used to produce air-mechanical foam. Depending on the area of ​​application, foam concentrates are divided into two classification groups: general purpose and special purpose. General purpose foam concentrates include: PO-3NP, PO-3AI TEAS. Foaming agents for specific purposes include: “Sampo”, “Morskoy”, “Potok”, “Film-forming”, “Foretol”, “Universal”, POF-9M.

Special purpose foam concentrates differ from general purpose foam concentrates in their higher fire extinguishing ability due to the use of recycled additives.

All foaming agents for general and special purposes do not lose their original physical and chemical properties during repeated freezing and subsequent gradual thawing.

Energy plants mainly use general purpose foaming agents.

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

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 . The following terms, definitions and established abbreviations are adopted in these Instructions:

AUPP - automatic foam fire extinguishing installation;

AUPS - automatic installation of fire alarm;

FPPT - 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;

PO - foaming agent;

PI - fire detector;

OK - check valve;

Control room - block control panel.

2. GENERAL PROVISIONS

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

2.2 . Local operating instructions for a specific fire extinguishing installation with air-mechanical foam are developed by the organization that set up this installation, together with the energy enterprise where it is used. If the adjustment was carried out by an energy enterprise, then the instructions are 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, devices and equipment included in the fire extinguishing installation.

2.4 . The local instructions must include relevant labor protection requirements and environmental measures to ensure safe operation, technical supervision and repair work at a specific fire extinguishing installation for personnel.

2.5 . Local regulations must be revised at least once every three years and each time after reconstruction of a foam fire extinguishing installation or in the event of a change in operating conditions.

3. SAFETY MEASURES WHEN OPERATING THE AUPP

3.1 . All rotating parts of PPT, NKR pumps must be enclosed with protective covers.

Cleaning or wiping pumps while they are in operation is prohibited.

3.2 . The electrical equipment of the pumps must have proper stationary grounding.

3.3 . Putting the equipment into operation, operations with fittings, sampling of the concentrated foaming agent and its solution must be carried out by at least two persons from the service areas.

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

Work with foaming agents 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 rinsed with plenty of running water.

3.5 . Repair work on the foam fire extinguishing station and on the system should be carried out only according to the order.

3.6 . During the period of personnel stay in the cable rooms (walk-through, repair work, etc.), the start-up of the fire extinguishing installation is switched to remote control mode. Upon completion of work in the protected premises, the automatic operating mode of the foam fire extinguishing installation is restored.

3.7 . When operating technological equipment of foam fire extinguishing installations, energy enterprise personnel must comply with the established safety requirements set out in PTE, PPB, PTB and in factory data sheets and operating instructions for specific equipment.

3.8 . It is prohibited to discharge foaming agent and its solutions into sewer systems and storm drains.

4. ORDER OF OPERATION OF AUPP

4.1 . An automatic foam fire extinguishing installation (AUPP) is designed to extinguish fires in protected premises and structures of an energy enterprise upon receiving a signal about its occurrence from fire detectors.

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

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

Schematic flow diagram of a fire pumping station with ready-made supply foaming agent solution:

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

Gate valve; - check valve.

Pipelines: foaming agent solution

water supply

foaming agent

solution circulation

compressed air

To characterize foam generators or foam sprinklers under different operating modes, in the fire extinguishing installation diagram it is recommended to install a special outlet on the pressure pipeline between the pump and the valve closest to the pump,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 foam concentrate or a reservoir for storing an aqueous solution of foam;

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

pipeline network;

pumps for collecting and supplying water or a ready-made aqueous foam solution;

shut-off 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 automatic control system may include:

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

a water tank for filling feed pumps;

pneumatic tank to maintain constant pressure in the automatic transmission network;

compressor for replenishing the pneumatic tank with air.

4.4 . Before filling the foam solution storage tanks, they must be inspected and cleaned internally. After this, 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, the following is monitored: leakage of the solution through the water indicator glasses of the tanks, absence of leaks in the circuit, and the level of the foaming agent in the tanks.

After this, the solution is analyzed and recorded in the operational log.

4.6 . The launch of the automatic propulsion system must be automatic. Switching the foam extinguishing installation to remote and manual mode is not allowed, except in cases of repair work of the installation.

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

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

4.8 . Devices for local start-up of a fire extinguishing installation are located in the pumping station room and at the control units of distribution pipelines and are intended for testing and setting up a fire extinguishing installation, as well as for starting the installation in the event of automatic and remote start failures.

4.9 . The control panel should contain a diagram of this installation with a brief description of the device and operation of the automatic control unit. The pumping station premises must contain instructions on the procedure for putting pumps into operation and opening shut-off valves, as well as a schematic and technological diagram.

4.10 . Control units and automatic control equipment must have 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 designed to extinguish fires of liquid (fire class B) and solid (fire class A) flammable substances. Foam is a cellular-film dispersed system consisting of a mass of gas or air bubbles separated by thin films of liquid.

Air-mechanical foam is obtained by mechanically mixing the foaming solution with air. The main fire extinguishing property of foam is its ability to prevent the entry of
into the combustion zone of flammable vapors and gases, as a result of which the combustion stops. The cooling effect of fire extinguishing foams also plays a significant role, 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 volume of foam to the volume of the foaming agent 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 expansion ratio of the resulting foam (Fig. 2.36).

Rice. 2.36. Classification of foam fire nozzles

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

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

The SVPE barrel (Fig. 2.37) 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 appropriate diameter, and on the other, a guide pipe is attached with screws 5 , made of aluminum alloy and designed to form air-mechanical foam and direct it to the source of the fire. There are three chambers in the barrel body: receiving 6 , vacuum 3 and day off 4 . There is a nipple on the vacuum chamber 2 with a diameter of 16 mm for connecting a hose 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 ejecting device 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 barrel (Fig. 2.38) is
in the next one. Foaming solution passing through the hole 2 in the barrel body 1 , creates in a conical chamber 3 vacuum, due to which air is sucked through eight holes evenly spaced in the guide pipe 4 trunk The air entering the pipe is intensively mixed with the foam-forming solution and forms a stream of air-mechanical foam at the exit from 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 SVPE barrel differs from SVP in that it is not the foam-forming solution that enters the receiving chamber, but water, which, passing through the central hole, creates a vacuum in the vacuum chamber. A foam agent is sucked into the vacuum chamber through a nipple through a hose from a backpack tank or other container. Technical characteristics of fire trunks for producing low expansion foam are presented in table. 2.24.

Table 2.24

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

Depending on the foam productivity, 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 body. The generator is a portable water-jet ejector apparatus and consists of the following main parts (Fig. 2.39): nozzle 1 , mesh package 2 , generator housing 3 with guide device, collector 4 and centrifugal sprayer 5 . The atomizer body, in which the atomizer is mounted, is attached to the generator manifold using three stands 3 and coupling head GM-70. Mesh Pack 2 It is a ring covered along the end planes with a metal mesh (mesh size 0.8 mm). Centrifugal sprayer 3 has six windows located at an angle of 12°, which causes swirling of the flow of working fluid and ensures a sprayed jet at the outlet. Nozzles 4 designed to form a foam stream after a package of meshes into a compact stream and increase the flight range of the foam. Air-mechanical foam is obtained by mixing three components in a generator in a certain proportion: water, foaming agent and air. A flow of foaming agent solution is fed under pressure into the sprayer. As a result of ejection, when a sprayed jet enters the collector, air is sucked in and mixed with the solution. A mixture of drops of foaming solution and air falls on the mesh package.

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

1 – nozzles; 2 – mesh package; 3 – generator housing;

4 – collector; 5 – centrifugal sprayer

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

Control 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 pressure losses in pressure hoses. Determination of pressure loss in hose lines.

5. Classification of hydraulic equipment. Its purpose. Device.

6. Classification of fire trunks. Purpose. Features of the supply of fire extinguishing agents.

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

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

9. Explain the difference in the principles of foam formation when feeding UHPE and SVP air-foam barrels.

10. Design of medium expansion foam generators. Main indicators of their technical characteristics.