Fire extinguisher

Test of a fire extinguisher Ramon de Banolas, St. Petersburg, 1881

In 1881, a “fire extinguisher” designed by Ramon de Banolas was successfully publicly tested at the Semyonovsky parade ground in St. Petersburg ^[2] .

The inventor of the foam fire extinguisher is considered to be Russian Alexander Laurent (1904).

Fire extinguishers are distinguished by the method of operation:

• automatic (self-working) - usually mounted permanently in places of a possible fire;
• manual (driven by a person) - are located on specially designed stands;
• universal (combined action) - combine the advantages of both of the above types.

Fire extinguishers are distinguished by the principle of exposure to the fire:

• gas (carbon dioxide, chladonic);
• foam (chemical, chemical air-foam, air-foam, air-emulsion);
• powder;
• air-emulsion.

By body volume:

• portable small cars with a fire extinguishing agent mass up to 4 kg;
• industrial portable with a mass of extinguishing agent from 4 kg;
• stationary and mobile with a mass of extinguishing agent from 8 kg.

By the method of supplying the extinguishing agent:

• under the pressure of water resulting from a chemical reaction of charge components;
• under the pressure of gases supplied from a special spray canister placed in (on) the body of the fire extinguisher;
• under pressure of gases previously pumped into the fire extinguisher body;
• under the own pressure of the extinguishing agent.

By the type of starting devices:

• with gate valve;
• with lever-type locking and starting device;
• with start-up from an additional pressure source.

Fire extinguishers are marked with letters characterizing the type and class of the fire extinguisher, and with numbers indicating the mass of the fire extinguisher in it.

Designed to extinguish fires with extinguishing foams: chemical or air-mechanical. Chemical foam is obtained from aqueous solutions of acids and alkalis , air-mechanical foam is formed from aqueous solutions and blowing agents by flows of working gas: air, nitrogen or carbon dioxide . Chemical foam consists of 80% carbon dioxide, 19.7% water and 0.3% foaming agent, air-mechanical from about 90% air, 9.8% water and 0.2% foaming agent .

Foam fire extinguisher was invented by Russian engineer Alexander Georgievich Laurent in 1902 - 1904. ^[3] Subsequently, in St. Petersburg, he opened the Eureka company, which began to manufacture and sell fire extinguishers under this brand (subsequently, Laurentin). Fire extinguishers of this brand were demonstrated at international exhibitions and were recognized as a very effective means of extinguishing both domestic fires and fires at industrial facilities. Laurent foam was a mixture of two powders and water combined in a foam generator. ^[4] These powders were sodium bicarbonate and aluminum sulfate . ^[5] The resulting chemical foam was a stable solution of their small bubbles containing carbon dioxide with a lower density than oil or water. Since this solution was lighter than combustible liquids, it flowed freely along the burning surface of the liquid and extinguished the fire, blocking the access of oxygen. ^[6]

Foam fire extinguishers are used for extinguishing with foam the starting fires of almost all solids, as well as combustible and some flammable liquids in an area of ​​not more than 1 m². It is impossible to extinguish the ignited electrical installations and power networks that are energized with foam, as it is a conductor of electric current. In addition, foam extinguishers should not be used in extinguishing alkali metals of sodium and potassium, because they interact with water in the foam and release hydrogen, which enhances combustion, as well as in quenching of alcohols, since they absorb water, dissolving in it, and when hit on them, the foam quickly collapses. Modern foam fire extinguishers use sodium azide as a gas-forming reagent, which easily decomposes with the release of a large amount of nitrogen.

The disadvantages of foam fire extinguishers include a narrow temperature range of use (5–45 ° C), high corrosivity of the charge, the possibility of damaging the extinguishing object, and the need for annual recharging.

During the First World War , tetrachloride fire extinguishers were widely used. Extinguishing with such a fire extinguisher needed to be done in gas masks - getting on hot surfaces, carbon tetrachloride was partially oxidized to phosgene , which is a potent toxic substance with a choking effect. But already at that time in other countries safer carbon dioxide fire extinguishers began to be used.

Currently, both manual (OU-5) and mobile carbon dioxide fire extinguishers (OU-400) are distinguished.

Carbon dioxide fire extinguishers in which liquefied carbon dioxide (carbon dioxide) is used as a fire extinguisher. Carbon dioxide fire extinguishers are available both manual and mobile. Manual fire extinguishers are identical in structure and consist of a steel high-strength balloon, in the neck of which a shut-off-trigger device of a valve or pistol type is screwed, a siphon tube that serves to supply liquefied carbon dioxide from the balloon to the shut-off-trigger device, and a snow blower. To actuate a carbon dioxide fire extinguisher, it is necessary to direct the bell-blower to the fire and turn the handwheel to the full or turn off the lever of the locking and starting device. During the transition of carbon dioxide from a liquid to a gaseous state, a volume increase of 400–500 times occurs, accompanied by a sharp cooling to a temperature of −72 ° C and partial crystallization; To avoid frostbite, do not touch the metal socket. The effect of flame extinguishing is achieved by lowering the temperature of the source of ignition below the ignition point and displacing oxygen from the combustion zone with non-combustible carbon dioxide.

Carbon dioxide fire extinguishers equipped with a metal bell cannot be used for extinguishing equipment under voltage due to the formation of a conductive carbonic acid solution during the operation of the fire extinguisher when carbon dioxide is dissolved in water resulting from the condensation of water vapor. Any carbon dioxide fire extinguishers must not be used to extinguish fires of electrical equipment under voltage above 10 kV.

Due to the significant cooling effect, carbon dioxide fire extinguishers do not extinguish equipment and pipelines with high operating temperatures. Temperature stresses caused by abrupt local cooling of the pipeline section or apparatus body can lead to depressurization or destruction of the latter. If the apparatus or piping contains explosive and flammable substances under pressure, this may result in secondary fire and explosion. For extinguishing hot pipelines and equipment, powder extinguishers are usually used.

See also Powder fire extinguishing .

Powder extinguishers are divided into:

• Class A (Solids): Conventional flammable combustible substances such as wood or paper
• Class B (Liquid): Flammable liquids such as gasoline, thinners or paints.
• Class C (Gaseous Substances): Combustible Gases
• Class D (Metals and Metallic Substances): Combustible metals such as titanium or magnesium
• Class E (live electrical equipment): Combustion of live electrical installations
• Class K: Vegetable oils, trans fats or fats

The most common universal fire extinguishers in terms of application and operating temperature range (especially with a charge of ABCE classes), they can be used to successfully extinguish almost all fire classes, including electrical equipment under voltage up to 1000 V. Fire extinguishers are not designed to extinguish fires alkali and alkaline earth metals and other materials, the combustion of which can occur without access of air.

Extinguishing Powders Used

Extinguishing powders are finely divided mineral salts with various additives that prevent caking and clumping. As a basis for fire extinguishing powders, ammonium phosphate salts (mono-, diammonium phosphates, ammophos ), sodium and potassium carbonate and bicarbonate, sodium and potassium chlorides, etc. are used. Organosilicon compounds, aerosil, white soot, metal stearates , nepheline , talc are used and others. Today, only hydrophobic types of additives are used, which prevents powder caking, such as hydrophobic aerosil and others.

Powders are stored in special packaging, protecting them from moisture. During storage, the powders are chemically inactive, do not have an abrasive effect. When exposed to fire extinguishing powder on ferrous and non-ferrous metals with normal humidity, corrosion does not occur. Corrosion of metals occurs only when the powder is wetted (moistened) on metal surfaces. The effect of fire extinguishing powder on the paintwork surfaces was not noted. The effect of fire extinguishing powder on polymeric materials (windings, braiding, plastic hoses, etc.), coupled with high temperatures, is highly aggressive and destructive.

The general hazard class of extinguishing powder is 3, 4.

Types of Powder Extinguishers

Powder extinguishers can be divided into injection and gas generation.

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Charged with a fire extinguishing powder and pumped with an inert gas (this can be nitrogen, carbon dioxide) or air under a pressure of about 16 atm. This type of fire extinguisher can extinguish: if the type of powder A , B, C, E - burning solids, burning liquids, flammable gases, electrical wiring under low voltage up to 1000 V, if the type of powder B, C - small fires of liquids and gases in easily accessible places . The design of this fire extinguisher includes a locking device that allows, without applying special effort, to apply powder to the flame by simply pressing the upper handle by hand or, releasing the handle, stop its flow. The advantage of this type of fire extinguisher is the internal pressure indicator mounted on the head of the fire extinguisher and showing its performance (green sector of the scale) in contrast to all other types of fire extinguishers. Their disadvantage is the tendency to caking powder in the container, which can cause a powder supply failure even in the presence of gas pressure.

Gas Generators

The principle of operation is to use the energy generated at the time of starting the gas to release the extinguishing agent. They can be used in any conditions as the primary means of extinguishing fires. In addition to the required waiting time (6 ... 10 sec.) At the first moment after the launch, they do not fundamentally differ from the injection fire extinguishers. Known and produced manual fire extinguishers with a pyrotechnic gas generator, to activate which you need to pull out the ring with the cord (see photo).

With ampoule source of displacing gas

They have in their design a hermetically sealed spray can (ampoule from an auto-siphon, airguns) and a drummer with a needle, which should pierce the membrane of the can, after which the flow of powder with compressed gas begins. The disadvantage of this design is the difficulty in diagnosing depressurization of the can during long-term storage.

Free-

A fairly rare type of powder fire extinguisher, which is a tall glass with a freely unscrewable lid at the top, to extinguish a fire, you need to unscrew the lid and pour the contents into the fire. Despite the inconvenience of this method, the difficulty of accurate application, (especially in a stressful situation), it is the only type of fire extinguisher with 100% reliability.

Features of the use of powder fire extinguishers

• You need to know the capabilities of your fire extinguisher - on each of them the fire extinguishing classes are indicated on the label such as: “A B C E” or “B C E”, the type of powder, for example, “ABC” or “BC”, must also be indicated. Even when buying, be sure to pay attention to this, because trying to extinguish a tree, rags, paper and plastic with a fire extinguisher, whose symbol “A” is crossed out on the label, and the type of powder is indicated as “ALL” is useless! This leads to re-ignition of the extinguished combustible material from residual smoldering or heated elements of building structures and equipment. It is the additives to the powder of the components that raise the rank of the fire extinguisher to the “ A B C E” classes and protect you from re-ignition of an already extinguished flame;
• Significant powder contamination of the protected object does not allow the use of powder fire extinguishers to protect computing rooms, electronic equipment, electrical equipment with rotating elements, museum exhibits, etc.
• As a result of the formation of a powder cloud during extinguishing, high dustiness forms and visibility decreases sharply (especially in small rooms), and also some people may experience an allergic reaction (especially strong when inhaled) to the components of the powder.
• Having a high dispersion, fire extinguishing powders during storage show a tendency to clumping and caking, which can lead to a loss of fire extinguishing ability. Therefore, when using powders in fire extinguishers, it is necessary to strictly observe the recommended storage mode, as well as remember the timing of checking the working pressure and the recharge time.

Self-actuating powder fire extinguishers

Designed for extinguishing without human intervention by fire extinguishing powders of the ABC type ignition of solid and liquid substances, petroleum products, electrical equipment under voltage up to 5000 volts, in small (up to 50 m³) rooms without people staying in them for a long time. If necessary, can be used instead of or together with portable ^[7] .

Air-emulsion fire extinguishers (OVE) - a highly effective, environmentally friendly and safe primary fire extinguishing agent. These are injection fire extinguishers designed to extinguish solid and liquid combustible materials, combustible gases, and electrical equipment under voltage up to 1000 V (types of fires: A, B, C, E). Work at temperatures from minus 40 ° C to +50 ° C.

The principle of operation is based on spraying the emulsion stream over the burning area, with the formation of a thin film of extinguishing composition on the damaged surface.

Главное преимущество воздушно-эмульсионных огнетушителей — минимальный расход огнетушащей жидкости, что снижает вторичный ущерб от её пролива. Огнетушители безопасны при использовании в закрытых помещениях с присутствием людей без применения средств индивидуальной защиты, не создают запылённости и снижения видимости.

• Fire
• Fire protection
• Огнезащита

• Лоран и огнетушитель (история изобретения)
• История огнетушителя
• Перезарядка огнетушителей: сроки