Gas extinguishing

Gas fire extinguishing in the server room. 1996 year

In the last quarter of the 19th century, carbon dioxide began to be used abroad as a fire extinguishing agent. This was preceded by the production of liquefied carbon dioxide (CO ₂ ) by M. Faraday in 1823. At the beginning of the 20th century, carbon dioxide fire extinguishing systems began to be used in Germany, a significant number of them appeared in the 30s. After World War II, installations using isothermal tanks for storing CO ₂ began to be used abroad (the latter were called low-pressure carbon dioxide fire extinguishing installations).

Freons (halons) are more modern gas fire extinguishing agents (GOTV). Abroad, in the beginning of the 20th century, halon 104, and then in the 30s, halon 1001 (methyl bromide) was very limitedly used for fire extinguishing, mainly in hand-held fire extinguishers. In the 1950s, research was carried out in the USA that made it possible to propose halon 1301 (trifluorobromomethane) for use in plants.

The first domestic gas fire extinguishing installations (UGP) appeared in the mid-30s to protect ships and ships. As gas OTV (GOTV) carbon dioxide was used. The first automatic UGP was used in 1939 to protect a turbogenerator of a thermal power plant. In 1951-1955 gas fire extinguishing batteries with pneumatic start (BAP) and electric start (BAE) are developed. The option of block execution of batteries with the help of type-setting sections of type CH is applied. Since 1970, the batteries have been used for the locking and starting device GZSM.

In recent decades, automatic gas fire extinguishing systems using

ozone-safe freons - Freon 23, Freon 227ea, Freon 125.

At the same time, Freon 23 and Freon 227еа are used to protect the premises in which people are or may be.

Freon 125 is used as a fire extinguishing agent to protect rooms without the constant presence of people.

Carbon dioxide is widely used to protect archives and cash vaults.

As extinguishing agents for extinguishing, gases are used, the list of which is defined in the Code of Rules SP 5.13130.2009 “Automatic fire alarm and fire extinguishing installations” (paragraph 8.3.1).

These are the following gas extinguishing agents: Freon 23, Freon 227еа, Freon 125, Freon 218, Freon 318C, nitrogen, argon, inergen, carbon dioxide, sulfur hexafluoride.

The use of gases that are not included in the specified list is allowed only according to additionally developed and agreed standards (specifications) for a particular facility (Code of Practice SP 5.13130.2009 “Automatic fire alarm and fire extinguishing installations” (note to table 8.1).

Gas extinguishing agents according to the principle of fire extinguishing are classified into two groups:

The first group of GOTV is inhibitors (chladones). They have a chemical based quenching mechanism

inhibition (retardation) of the combustion reaction. Once in the combustion zone, these substances decay intensively

with the formation of free radicals that react with the primary combustion products.

In this case, the burning rate decreases to complete attenuation.

The extinguishing concentration of freons is several times lower than for compressed gases and ranges from 7 to 17 volume percent.

Freons recommended in the Code of Rules SP 5.13130.2009 for use,

namely, Freon 23, Freon 125, Freon 227ea are ozone-depleting.

The ozone-depleting potential (ODP) of HFC 23, HFC 125 and HFC 227 ea is 0.

Greenhouse gases.

The second group is atmospheric diluting gases. These include compressed gases such as argon, nitrogen, inergen.

To maintain combustion, the presence of at least 12% oxygen is a prerequisite. The principle of diluting the atmosphere is that when compressed gas (argon, nitrogen, inergen) is introduced into the room, the oxygen content decreases to less than 12%, that is, conditions are created that do not support combustion.

Liquefied gas fire extinguishing compositions

Liquefied gas Freon 23 is used without propellant.

Freons 125, 227еа, 318Ц to ensure transportation through pipe wiring to the protected room require pumping gas propellant.

Carbon dioxide

Carbon dioxide is a colorless gas with a density of 1.98 kg / m³, odorless and not supporting the combustion of most substances. The mechanism of the cessation of combustion of carbon dioxide is its ability to dilute the concentration of reacting substances to the extent that combustion becomes impossible. Carbon dioxide can be emitted into the combustion zone in the form of a snowy mass, while providing a cooling effect. From one kilogram of liquid carbon dioxide, 506 liters are formed. gas. A fire extinguishing effect is achieved if the concentration of carbon dioxide is at least 30% by volume. The specific gas flow rate will be 0.64 kg / (m³ · s) ^[1] . It requires the use of weighing devices to control the leakage of a fire extinguishing agent, usually it is a tensor weighing device.

It can not be used to extinguish alkaline earth, alkali metals, some metal hydrides, developed fires of smoldering materials ^[2] .

Freon 23

Freon 23 (trifluoromethane) - a light gas without color and odor. The modules are in the liquid phase. It has a high vapor pressure (48 KgS / sq.cm), does not require pressurization with a propellant. Gas escapes from cylinders under the influence of vapor pressure. GOTV mass control in the cylinder is carried out by the mass control device automatically and constantly, which provides constant monitoring of the fire extinguishing system operability. A fire extinguishing station is capable of creating a normative fire extinguishing concentration in a standard time (up to 10 seconds) in rooms that are up to 110 meters horizontal and 32 - 37 meters vertical from modules with GOTV. Distance data is determined using hydraulic calculations. The properties of gas Freon 23 allow you to create a fire extinguishing system for objects with a large number of protected premises by creating a centralized gas fire extinguishing station. Ozone Safe - ODP = 0 (Ozone Depletion Potential). The maximum permissible concentration is 50%, the standard quenching concentration is 14.6%. Safety margin for people is 35.6%. This allows the use of Freon 23 to protect rooms with people.

Freon 125

- chemical name - pentafluoroethane, ozone-safe, symbolic designation - R - 125 HP.
- colorless gas, liquefied under pressure; incombustible and low toxicity.
- Designed as a refrigerant and extinguishing agent.

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Freon 218

Freon 227ea

Freon 227еа [C ₃ F ₇ H (CF ₃ CFHCF ₃ )] - colorless gas, used as a component of mixed freons, gas dielectric, propellant and fire extinguisher

(foaming and cooling agent). Freon 227еа is ozone-safe, ozone-depleting potential (ODP) - 0 There is an example of the use of this gas in a server automatic gas fire extinguishing installation, in the MPX65-120-33 gas fire extinguishing module.

Non-combustible, non-explosive and low toxic gas, under normal conditions is a stable substance. In contact with the flame and with surfaces with a temperature of 600 ° C and above, Freon 227ea decomposes with the formation of highly toxic products. If a liquid product gets on the skin, frostbite is possible.

Pour into cylinders with a capacity of up to 50 dm ³ in accordance with GOST 949, designed for a working pressure of at least 2.0 MPa, or in containers (barrels) with a capacity of not more than 1000 dm ³ , designed for an excess working pressure of at least 2.0 MPa. At the same time, for every 1 dm ^{3 of the} tank capacity, not more than 1.1 kg of liquid refrigerant should be filled. Transported by rail and road.

Store in warehouses away from heating appliances at a temperature not exceeding 50 ° C and in open areas, providing protection from direct sunlight.

Freon 318Ts

Freon 318ts (R 318ts, perfluorocyclobutane) Freon 318Ts - liquefied under pressure, non-combustible, non-explosive. Chemical formula - C ₄ F ₈ Chemical name: octafluorocyclobutane Physical state: gas without color with a slight odor Boiling point −6.0 ° C (minus) Melting point −41.4 ° C (minus) Auto-ignition temperature 632 ° C Molecular mass 200.031 Ozone Depletion Potential (ODP) ODP 0 Global warming potential GWP 9100 MPC r.z.mg / m3 r.z. 3000 ppm Hazard class 4 Fire hazard rating Fireproof gas. In contact with flame, decomposes with the formation of highly toxic products. There is no ignition area in the air. In contact with flame and hot surfaces, decomposes with the formation of highly toxic products. At high temperature, reacts with fluorine. Application Flame arrester, a working substance in air conditioners, heat pumps, as a refrigerant, gas dielectric, propellant, reagent for dry etching in the manufacture of integrated circuits.

Compressed gas fire extinguishing compounds (Nitrogen, Argon, Inergen)

Nitrogen

Nitrogen is used for the phlegmatization of combustible vapors and gases, for purging and draining containers and apparatus from residues of gaseous or liquid combustible substances. Cylinders with compressed nitrogen in the conditions of a developed fire are dangerous, since their explosion is possible due to a decrease in the strength of the walls at high temperature and an increase in the gas pressure in the cylinder when heated. An explosion prevention measure is the release of gas into the atmosphere. If this is not possible, the cylinder should be abundantly irrigated with water from the shelter ^[3] .

Nitrogen can not be used to extinguish magnesium, aluminum, lithium, zirconium and other materials that form nitrides with explosive properties. In these cases, argon is used as an inert diluent, and helium is much less common ^[4] .

Argon

Inergen

Inergen is an environmentally friendly fire-fighting system whose active element consists of gases already present in the atmosphere. Inergen is inert, that is, non-liquefied, non-toxic and non-combustible gas. It consists of 52% nitrogen, 40% argon, and 8% carbon dioxide. This means that it does not harm the environment and does not damage equipment and other objects.

The extinguishing method inherent in Inergen is called “oxygen substitution” - the oxygen level in the room drops and the fire goes out.

• The Earth’s atmosphere contains approximately 20.9% oxygen.
• The oxygen substitution method is to lower the oxygen level to about 15%. At this level of oxygen, the fire in most cases is unable to burn and goes out within 30-45 seconds.
• A distinctive feature of Inergen is its content of 8% carbon dioxide.

Water vapor

One of the first extinguishing experiments was carried out in 1879 at the Russian-Baltic Carriage Works in Riga . A light plank building 36 feet long, 16 feet wide and 9 feet high to the base of the roof, up to a 16 foot ridge, was connected to the steam boiler with a 1½ inch metal pipe that ended in the middle of the building. The shavings and wood that filled the building were ignited and a valve on the pipe was opened. Despite the fact that the steam had a pressure of 5 atm, it did not have a noticeable effect on the flame inside the building. It was suggested that the extinguishing failed due to cracks in the walls and roof. The whole structure was sheathed with a new series of boards and the experiment was repeated. The flame diminished, but was not finally extinguished. In the following experiment, a 1½ inch pipe was replaced with a 4 inch pipe. The flame was extinguished as a result ^[5] .

Steam to extinguish fires began to be used primarily on ships. At industrial facilities, fire extinguishing with steam has been used since the mid-20s. mainly in flour and oat-peeling plants of the Urals and Trans-Urals. In the journal “Soviet flour milling and baking” (1931, No. 8), engineer V. I. Voinov described fire extinguishing installations and field experiments existing at that time to extinguish a fire with steam, and also gave an approximate methodology for calculating plants ^[6] .

The fire extinguishing system is based on the fact that the steam introduced into the room in which the fire occurred reduces the oxygen content in the combustion zone. The working medium in the system is saturated water vapor with a pressure of not more than 8 · 10 ⁵ Pa ^[7] .

Along with dilution of the oxygen concentration, this also causes some cooling of the combustion zone, as well as a mechanical flame failure by steam jets. If the enclosing structures and equipment are heated above the vapor condensation temperature at atmospheric pressure, the quenching effect is achieved by the volumetric concentration of steam equal to 35%. At lower temperatures, intense vapor condensation occurs and the fire may not be extinguished. Steam consumption is taken into account its possible condensation depending on the tightness of the premises ^[6] .

Saturated steam is preferred, although superheated is also used. Along with the dilution action, water vapor cools technological devices heated to a high temperature without causing sharp temperature stresses, and steam supplied in the form of compact jets is capable of mechanically breaking off the flame ^[8] .

Perforated pipes are used as internal distribution steam pipelines of stationary extinguishing systems in enclosed spaces. The holes in the perforated pipes for the release of steam should be 4..5 mm in diameter. To drain the condensate from the supplying steam pipelines and steam inlets, downcomers should be provided, located in the lowest places along the pipe slope so that both the condensate and the steam jets do not interfere with the actions of the operating personnel.

To supply steam to enclosed spaces, perforated pipes are laid around the entire inner perimeter of the room at a height of 0.2..0.3 m from the floor. In this case, the pipe openings are arranged so that the steam jets emerging from them are directed horizontally into the room. When calculating the fire extinguishing systems, the steam supply rate is taken as the main indicator ^[9] . For the estimated extinguishing time, they take the period of time from the moment the steam is extinguished (with a given intensity) until the combustion is completely eliminated. It should not exceed three minutes ^[10] .

The fire steam curtain is designed to prevent the contact of combustible gas mixtures formed during accidents at the enterprises of the petrochemical and gas industry with ignition sources (for example, heating furnaces). The curtain must have sufficient density and range, excluding the leakage of the combustible mixture into the protected area of ​​the object ^[11] .

A device for creating a steam curtain is an annular tubular collector, along the axis of which holes of the same diameter are drilled along the entire upper part at an equal distance from each other. The collector is located on metal, concrete or brick supports. The collector must have drainage valves to drain condensate or precipitation. A rigid gas-tight fence (sheet metal or brick wall) is installed along the collector axis to prevent the leakage of the combustible mixture between the individual jets in the initial section of the curtain. Apertures in fences should be constantly closed by dense doors.

The trajectory of the air curtain should exceed the protected area. For tall objects, the curtain can be multi-sectional in the vertical direction. To ensure uniform distribution of steam along the length of the collector, it is necessary that the ratio of the total area of ​​the holes to the cross-sectional area of ​​the collector be less than or equal to 0.3 ^[12] .

The inclusion of an external steam curtain is provided in the following cases:

• at visual detection of an accident with the leakage of flammable liquids, vapors and gases from the technological equipment of the installation;
• upon receipt of a signal from a flame extinguishing control device installed on the furnace on the burners of the furnace, which can occur when a vapor-gas mixture with insufficient oxygen content is sucked in from the atmosphere instead of air;
• upon receipt of signals from gas analyzers (signaling devices) of combustible gases and vapors installed at dangerous points;
• when reporting emergency gas contamination at adjacent technological installations ^[13] .

Heating tube furnaces are equipped with a steam extinguishing system and steam curtains ^[14] .

Помещения насосных, перекачивающих легковоспламеняющиеся и горючие жидкости, объёмом до 500 м³ должны оборудоваться стационарными системами паротушения, если не предусмотрена стационарная система пенотушения ^[15]

На производстве по переработке древесных смол с процессом периодической разгонки смолы и всплавных смоляных масел топка печи и камеры двойников должны быть оборудованы установками паротушения. Вентиль паротушения должен быть расположен в удобном для обслуживания и безопасном в пожарном отношении месте на расстоянии не менее 10 м от печи ^[18] .

В установках пиролиза и энергохимического использования древесины сушилка, бункер для пыли и газоходы газогенераторных установок должны быть оборудованы паровыми системами пожаротушения ^[19] .

Системой паротушения оборудуют грузовые трюмы, малярные, кладовые для хранения легковоспламеняющихся материалов тех судов, которые имеются паровые котлы достаточной производительности. На вновь строящихся речных судах система паротушения не применяются ^[7] .

Система применяется для тушения пожара в глушителях двигателей внутреннего сгорания, дымоходов паровых котлов, каналов вытяжной вентиляции, топливных цистернах, расположенных выше второго дна. В состав системы входит распределительный коллектор и контрольно-измерительные приборы, которые расположены на станции паротушения, трубопроводы. На станцию пар поступает от главных или вспомогательных котлов. Также пар может подаваться с берега, дока или другого судна. Для приема пара предусматривают приемные устройства, располагаемые с обоих бортов в районе станции паротушения или вспомогательных котлов ^[20] .

Ледокол «Россия» имеет систему тушения паром давлением 500 кПа (5 кгс/см2) предназначено для топливных цистерн, глушителей РДГ и АДГ, малярной, дымохода котла ^[21] .

Недостатки системы паротушения:

• можно применять только в закрытых помещениях и под котлами;
• приводит к порче грузов и механизмов (они смачиваются за счёт конденсации пара);
• опасно для жизни людей, особенно в том случае, когда, например, горит уголь, селитра, карбид кальция, которые образуют гремучий газ, легко взрывающийся ^[22] .

Применение пара на морских судах в дополнение к требуемому огнетушащему веществу может быть допущено Регистром в каждом конкретном случае. При этом производительность котла или котлов, обеспечивающих подачу пара, должна быть не менее 1,0 кг/ч на каждые 0.75 м³ валового объёма наибольшего из защищаемых паром помещений ^[23] .

Системы газового пожаротушения применяются в тех случаях, когда применение воды может вызвать короткое замыкание или иное повреждение оборудования — в серверных комнатах , хранилищах данных, библиотеках, музеях, на летательных аппаратах.

Автоматические установки газового пожаротушения должны обеспечивать:

• своевременное обнаружение пожара автоматической установкой пожарной сигнализации, входящей в состав автоматической установки газового пожаротушения;
• возможность задержки подачи газового огнетушащего вещества в течение времени, необходимого для эвакуации людей из защищаемого помещения;
• создание огнетушащей концентрации газового огнетушащего вещества в защищаемом объёме или над поверхностью горящего материала за время, необходимое для тушения пожара ^[24] .

В защищаемом помещении, а также в смежных, имеющие выход только через защищаемое помещение, при срабатывании установки должны включаться устройства светового (световой сигнал в виде надписей на световых табло «Газ — уходи!» и «Газ — не входить!») и звукового оповещения в соответствии с ГОСТ 12.3.046 и ГОСТ 12.4.009 ^[25] .

Система газового пожаротушения также входит как составная часть в системы подавления взрывов, используется для флегматизации взрывоопасных смесей.

Испытания автоматических установок газового пожаротушения

Испытания следует проводить:

• перед сдачей установок в эксплуатацию;
• в период эксплуатации не реже одного раза в 5 лет

Кроме того, масса ГОС и давление газа-вытеснителя в каждом сосуде установки следует проводить в сроки, установленные технической документацией на сосуды (баллоны, модули).

Испытания установок по проверке времени срабатывания, продолжительности подачи ГОС и огнетущащей концентрации ГОС в объёме защищаемого помещения не являются обязательными. Необходимость их экспериментальной проверки определяет заказчик или, в случае отступления от норм проектирования, влияющих на проверяемые параметры, должностные лица органов управления и подразделений Государственной противопожарной службы при осуществлении государственного пожарного надзора. ^[26]

Противопожарная установка «Штурм» совместного производства нижнетагильского ОАО «Уралкриомаш», московского опытно-конструкторского бюро «Гранат» и екатеринбургского производственного объединения «Уралтрансмаш» тушит крупный пожар на газовой скважине всего за 3-5 секунд. Таков результат испытаний установки на пожарах в местах газовых месторождений Оренбургской и Тюменской областей. Столь высокая эффективность достигается за счет того, что «Штурм» гасит пламя не пеной, порошком или водой, а сжиженным азотом, который выбрасывается в очаг пожара через сопла, установленные полукругом на длинной стреле. Азот оказывает двойное действие: полностью перекрывает доступ кислорода и охлаждает источник огня, не давая ему разгораться. Обычными средствами огонь на нефтегазовых объектах порой не удается погасить месяцами. «Штурм» сделан на базе самоходной артиллерийской установки, которая без труда преодолевает самые сложные препятствия на пути к труднодоступным участкам газопроводов и нефтяным скважинам. ^[27]

Фторкетоны — новый класс химических веществ, разработанных компанией 3М и введенных в международную практику. Фторкетоны — это синтетические органические вещества, в молекуле которых все атомы водорода заменены на прочно связанные с углеродным скелетом атомы фтора. Такие изменения делают вещество инертным с точки зрения взаимодействия с другими молекулами. Многочисленные тестовые испытания, проведенные ведущими международными организациями, показали, что фторкетоны не только являются отличными огнетушащими веществами (с эффективностью аналогичной хладонам), но и демонстрируют положительный экологический и токсикологический профиль.

• Азотное пожаротушение