The principle of operation of gas fire extinguishing. Automatic gas fire extinguishing, areas of application, characteristics of systems Fire extinguishing cylinder

For the first time, fire extinguishing gas began to be used at the end of the 19th century. And the first in installations gas fire extinguishing(UGP) was carbon dioxide. At the beginning of the last century, the production of carbon dioxide plants began in Europe. In the thirties of the twentieth century, fire extinguishers with freons, extinguishing agents such as methyl bromide, were used. For the first time in the Soviet Union, devices using gas to extinguish a fire. In the 40s, isothermal tanks began to be used for carbon dioxide. Later, new extinguishing agents based on natural and synthetic gases were developed. They can be classified as freons, inert gases, carbon dioxide.

Advantages and disadvantages of fire extinguishing agents

Gas installations are significantly more expensive than systems that use steam, water, powder or foam as an extinguishing agent. Despite this, they are widely used. The use of UGP in archives, storerooms of museums and other storage facilities with combustible values ​​is beyond competition, due to the practical absence of material harm from their use.

Besides . Powder and foam can ruin expensive equipment. Gas is also used in aviation.

The speed of gas propagation, the ability to penetrate into all cracks, allows the use of installations based on it to ensure the safety of premises with a complex layout, dropped ceilings, many partitions and other obstacles.

The use of gas installations operating on the basis of diluting the atmosphere of the object requires working together With complex systems security. For guaranteed extinguishing of a fire, all doors and windows must be closed and forced or natural ventilation must be turned off. To alert people inside the premises, light, sound or voice signals are given, certain time to exit. After that, fire extinguishing begins directly. Gas fills the premises, regardless of the complexity of its layout, within 10-30 seconds after the evacuation of people.

Plants using compressed gas can be used in unheated buildings, as they have a wide temperature range, -40 - +50 ºС. Some GFFS are chemically neutral, do not pollute the environment, and freon 227EA, 318C can also be used in the presence of people. Nitrogen plants are effective in the petrochemical industry, when extinguishing fires in wells, mines and other facilities where explosive situations are possible. Installations with carbon dioxide can be used with operating electrical installations with voltages up to 1 kV.

Disadvantages of gas fire extinguishing:

• the use of GFFS is ineffective in open areas;
• gas is not used to extinguish materials that can burn without oxygen;
• for large objects, gas equipment requires a separate special extension to accommodate gas tanks and related equipment;
• nitrogen plants are not used for extinguishing aluminum and other substances that form nitrides, which are explosive;
• it is impossible to use carbon dioxide for extinguishing alkaline earth metals.

Gases used to extinguish fires

In Russia, the types of gas fire extinguishing agents permitted for use in the UGP are limited to nitrogen, argon, inergen, freons 23, 125, 218, 227ea, 318C, carbon dioxide, sulfur hexafluoride. The use of other gases is possible upon agreement of technical conditions.

Gas extinguishing agents (GFFS) are divided into two groups according to the method of extinguishing:

• The first is freons. They extinguish the flame by chemically slowing down the burning rate. In the combustion zone, freons disintegrate and begin to interact with the combustion products, this reduces the burning rate until it completely dies out.
• The second is gases that reduce the amount of oxygen. These include argon, nitrogen, inergen. Most materials require more than 12% oxygen in a fire atmosphere to sustain combustion. By introducing an inert gas into the room and reducing the amount of oxygen, the required result is obtained. What kind of extinguishing agent in gas fire extinguishing installations must be used depends on the object of protection.

Note!

By storage type, GFFS are divided into compressed (nitrogen, argon, inergen) and liquefied (all others).

Fluoroketones are a new class of fire extinguishing agents developed by 3M. These are synthetic substances that are similar in efficiency to freons and are inert due to their molecular structure. The extinguishing effect is obtained at concentrations of 4-6 percent. Due to this, it becomes possible to use it in the presence of people. In addition, unlike freons, fluoroketones rapidly decompose after use.

Types of gas fire extinguishing systems

Gas fire extinguishing installations (UGP) are of two types: station and modular. To ensure the safety of several rooms, a modular UGP is used. For the whole facility, a station installation is usually used.

UGP components: gas fire extinguishing modules (MGP), nozzles, switchgear, pipes and GFFS.

The main device on which the functioning of the installation depends is the IHP module. It is a reservoir with a locking and starting device (ZPU).

In work, it is better to use cylinders with a capacity of up to 100 liters, since they are easy to transport and registration with Rostekhnadzor is not required.

Currently on Russian market more than a dozen domestic and foreign companies apply IHL.

Top 5 IHL Modules

• OSK Group is a Russian manufacturer of fire extinguishing devices with 17 years of experience in this area. The company manufactures devices using Novec 1230. This extinguishing agent is used in gas fire extinguishing installations, which can be used in energy and similar premises in the presence of people. ZPU with pressure gauge and safety bursting disc. Available in volumes from 8 liters to 368 liters.
• MINIMAX modules from German manufacturer are particularly reliable due to the use of seamless vessels. Line of MGP from 22 to 180 liters.

• Welded tanks are used in MGP, developed by VFAspekt. low pressure, as GOTV - freons. Available in 40, 60, 80 and 100 liters.
• MGP "Plamya" are produced by NTO "Plamya" company. Tanks for low pressure compressed gases and freons are used. Available in a large range from 4 to 140 liters.
• Modules from the Spetsavtomatika company are manufactured for high and low pressure compressed gases and freons. The equipment is easy to maintain and efficient in operation. 10 standard sizes of MGP are produced from 20 to 227 liters.

In the modules of all manufacturers, except for electric and pneumatic start-up, manual start of devices is provided.

The use of new gaseous fire extinguishing agents such as Novec 1230 (fluoroketone group), as a result, the possibility of extinguishing a fire in the presence of people increased the effectiveness of the UGP due to early response. And the harmlessness of using GFFS for material assets, despite the significant cost of equipment and its installation, becomes a serious argument in favor of using gas fire extinguishing systems.

24.12.2014, 09:59

S. Sinelnikov
head of the design department of Technos-M + LLC

Recently in systems fire safety small objects to be protected by systems automatic fire extinguishing, automatic gas fire extinguishing installations are becoming more and more widespread.

Their advantage lies in fire-extinguishing compositions that are relatively safe for humans, complete absence of damage to the protected object when the system is triggered, repeated use of equipment and extinguishing the source of fire in hard-to-reach places.

When designing installations, the most common questions arise regarding the choice of fire extinguishing gases and the hydraulic calculation of installations.

In this article we will try to reveal some aspects of the problem of choosing a fire extinguishing gas.

All the most commonly used in modern gas fire extinguishing installations are gas fire extinguishing agents can be roughly divided into three main groups. These are substances of the freon series, carbon dioxide - commonly known as carbon dioxide (CO2) - and inert gases and mixtures thereof.

In accordance with NPB 88-2001 *, all these gaseous fire extinguishing agents are used in fire extinguishing installations for extinguishing fires of class A, B, C, according to GOST 27331, and electrical equipment with a voltage not higher than that specified in the technical documentation for the used GFS.

Gas fire extinguishing systems are mainly used for volumetric fire extinguishing in the initial stage of a fire in accordance with GOST 12.1.004-91. Also, GFFS are used for phlegmatization of an explosive atmosphere in the petrochemical, chemical and other industries.

GFFS are non-conductive, easily evaporate, do not leave traces on the equipment of the protected object, in addition, an important advantage of GFFS is their

suitability for extinguishing expensive electrical installations energized.

It is prohibited to use GFFS for extinguishing:

a) fibrous, loose and porous materials capable of spontaneous combustion with subsequent smoldering of the layer inside the volume of the substance ( sawdust, rags in bales, cotton, grass flour, etc.);

b) chemicals and their mixtures, polymer materials those prone to smoldering and burning without air access (nitrocellulose, gunpowder, etc.);

c) chemically active metals (sodium, potassium, magnesium, titanium, zirconium, uranium, plutonium, etc.);

d) chemicals capable of undergoing external decomposition (organic peroxides and hydrazine);

e) metal hydrides;

f) pyrophoric materials (white phosphorus, organometallic compounds);

g) oxidants (nitrogen oxides, fluorine). It is forbidden to extinguish class C fires if, in this case, it is possible to release or enter the protected volume of combustible gases with the subsequent formation of an explosive atmosphere.

In the case of using GOTV for fire protection electrical installations should take into account the dielectric properties of gases: dielectric constant, electrical conductivity, dielectric strength.

As a rule, the limiting voltage at which it is possible to carry out extinguishing without turning off the electrical installations by all GEF is no more than 1 kV. For extinguishing electrical installations with voltages up to 10 kV, only premium CO2 can be used - in accordance with GOST 8050.

Depending on the extinguishing mechanism, gas fire extinguishing compositions are divided into two qualification groups:

1) inert diluents that reduce the oxygen content in the combustion zone and form an inert environment in it (inert gases - carbon dioxide, nitrogen, helium and argon (types 211451, 211412, 027141, 211481);

2) inhibitors that inhibit the combustion process (halocarbons and their mixtures with inert gases - freons).

Depending on the state of aggregation, gas fire extinguishing compositions under storage conditions are divided into two classification groups: gaseous and liquid (liquids and / or liquefied gases and solutions of gases in liquids).

The main criteria for choosing a gas extinguishing agent are:

■ Human safety.

■ Technical economic indicators.

■ Preservation of equipment and materials.

■ Restriction of use.

■ Impact on the environment.

■ Possibility to remove GFFS after application.

It is preferable to use gases that:

■ have acceptable toxicity in the used fire extinguishing concentrations (breathable and allow personnel to be evacuated even when gas is supplied);

■ thermally stable (form a minimum amount of thermal decomposition products, which are corrosive, irritating to the mucous membrane and poisonous if inhaled);

■ most effective in fire extinguishing (they protect the maximum volume when supplied from a module that is filled with gas up to the maximum value);

■ economical (provide minimum specific financial costs);

■ environmentally friendly (do not have a destructive effect on the ozone layer of the Earth and do not contribute to the creation of the greenhouse effect);

■ provide generic methods filling modules, storage and transportation and refueling. The most effective in extinguishing a fire are chemical gases called freons. The physicochemical process of their action is based on two factors: chemical inhibition of the oxidation reaction process and a decrease in the concentration of the oxidant (oxygen) in the oxidation zone.

Freon-125 has undoubted advantages. According to NPB 882001 *, the standard fire extinguishing concentration of HFCL-125 for class A2 fires is 9.8% by volume. This concentration of Freon-125 can be increased to 11.5% by volume, while the atmosphere is breathable for 5 minutes.

If we rank GFFS in terms of toxicity in case of a massive leak, then the least dangerous compressed gases since carbon dioxide protects humans from hypoxia.

The freons used in the systems (according to NPB 88-2001 *) are low-toxic and do not show a pronounced pattern of intoxication. In terms of toxicokinetics, freons are similar to inert gases. Only with prolonged inhalation exposure to low concentrations of freons can adversely affect the cardiovascular, central nervous system, lungs. With the inhalation of high concentrations of freons, oxygen starvation develops.

Below is a table with the temporary values ​​of a person's safe stay in the environment of the most frequently used brands of freons in our country at various concentrations (Table 1).

The use of halons in extinguishing fires is practically safe, because fire-extinguishing concentrations for freons are an order of magnitude less than lethal concentrations with a duration of exposure up to 4 hours. Approximately 5% of the mass of freon supplied to extinguish the fire undergoes thermal decomposition, therefore the toxicity of the environment formed when extinguishing the fire with freons will be much lower than the toxicity of pyrolysis and decomposition products.

Freon-125 is ozone-safe. In addition, it has maximum thermal stability in comparison with other freons, the temperature of thermal decomposition of its molecules is more than 900 ° C. The high thermal stability of freon-125 allows it to be used to extinguish fires of smoldering materials, because at a smoldering temperature (usually about 450 ° C), thermal decomposition practically does not occur.

Freon-227ea is no less safe than freon-125. But their economic performance as part of a fire extinguishing installation is inferior to Freon-125, and the efficiency (protected volume from a similar module) differs insignificantly. It is inferior to Freon-125 in terms of thermal stability.

The specific costs of CO2 and freon-227ea practically coincide. CO2 is thermally stable when extinguishing fire. But the efficiency of CO2 is not high - a similar module with HFC-125 protects the volume 83% more than the CO2 module. The fire extinguishing concentration of compressed gases is higher than that of freons, therefore, 25-30% more gas is required, and, therefore, the number of containers for storing gaseous fire extinguishing substances increases by a third.

Effective fire extinguishing is achieved at a CO2 concentration of more than 30% vol., But such an atmosphere is unsuitable for breathing.

Carbon dioxide at concentrations of more than 5% (92 g / m3) has a harmful effect on human health, the volume fraction of oxygen in the air decreases, which can cause the phenomenon of oxygen deficiency and suffocation. When the pressure drops to atmospheric pressure, liquid carbon dioxide turns into gas and snow with a temperature of -78.5 ° C, which cause frostbite of the skin and damage to the mucous membrane of the eyes.

Also, when using coal automatic fire extinguishing acid installations ambient temperature working area should not exceed + 60 ° C.

In addition to freons and CO2, inert gases (nitrogen, argon) and their mixtures are used in gas fire extinguishing installations. The unconditional environmental friendliness and safety for humans of these gases are the undoubted advantages of their use in AUGPT. However, the high fire extinguishing concentration and the associated larger (compared to freons) amount of required gas and, accordingly, a larger number of modules for its storage, make such installations more bulky and expensive. In addition, the use of inert gases and their mixtures in AUGPT is associated with the use of a higher pressure in the modules, which makes them less safe during transportation and operation.

V last years modern fire extinguishing agents of a new generation began to appear on the domestic market.

These special formulations are predominantly produced abroad and, as a rule, have a high cost. However, their low fire extinguishing concentration, environmental friendliness and the possibility of using modules with low pressure make their use attractive and promise good prospects for the use of such GFFS in the future.

Based on all of the above, we can say that the most effective and available fire extinguishing agents at this time are freons. Relatively high price freons is compensated by the cost of the installation itself, installation of the system and its Maintenance... Especially important quality freons used in fire extinguishing systems (in accordance with NPB 88-2001 *), their minimum harmful effect per person.

Tab. 2. Summary table of characteristics of the most commonly used GFETs on the territory of the Russian Federation

Gas fire extinguishing installations are specific, expensive and rather complicated to design and install. Today there are many companies that offer various settings gas fire extinguishing. Since there is little information in open sources on gas fire extinguishing, many companies mislead the customer, exaggerating the advantages or hiding the disadvantages of certain gas fire extinguishing installations.

What is gas fire suppression? Automatic installations gas fire extinguishing (AUGPT) or gas extinguishing modules (MGP) are designed to detect, localize and extinguish a fire of solid combustible materials, flammable liquids and electrical equipment in industrial, warehouse, household and other premises, as well as to issue a signal fire alarm in a room with round-the-clock stay of the duty personnel. Gas fire extinguishing installations are capable of extinguishing a fire anywhere in the volume of the protected room. Gas fire extinguishing, unlike water, aerosol, foam and powder, does not cause corrosion of the protected equipment, and the consequences of its use are easily eliminated by simple ventilation. At the same time, unlike other systems, AUGPT installations do not freeze and are not afraid of heat. They operate in the temperature range: from -40C to + 50C.

In practice, there are two methods of gas fire extinguishing: volumetric and local volumetric, however, the most widespread method is the volumetric method. Taking into account the economic point of view, the local volumetric method is beneficial only in cases where the volume of the room is more than six times the volume occupied by the equipment, which is usually protected using fire extinguishing installations.

System composition

Fire extinguishing gas compositions for fire extinguishing systems are used as part of an automatic gas fire extinguishing installation ( AUGPT), which consists of basic elements, such as: modules (cylinders) or containers for storing gaseous fire extinguishing agent, fire extinguishing gas charged into modules (cylinders) under pressure in a compressed or liquefied state, control units, pipeline, outlet nozzles that ensure delivery and release of gas into the protected area, control panel, fire detectors.

Design gas fire extinguishing systems produced in accordance with the requirements of fire safety standards for each specific facility.

Types of OTV used

Liquefied gas fire extinguishing compositions: Carbon dioxide, Freon 23, Freon 125, Freon 218, Freon 227ea, Freon 318C

Compressed gas extinguishing agents: Nitrogen, argon, inergen.

Freon 125 (HFC-125) - physicochemical characteristics

OTV Freon 227ea

Freon-227ea is one of the most used agents in the global gas fire extinguishing industry, also known as FM200. Used to extinguish fires in the presence of people. An environmentally friendly product that has no restrictions on long-term use. It has more efficient extinguishing performance and a higher cost of industrial production.

Under normal conditions, it has a lower (in comparison with Freon 125) boiling point and pressure saturated vapors, which increases safety in use and transportation costs.

Gas fire extinguishing Freon is an effective remedy for extinguishing a fire in premises, because gas instantly penetrates into the most hard-to-reach places and fills the entire volume of the room. The consequences of the activation of the Halon gas fire extinguishing installation are easily eliminated after smoke removal and ventilation.

The safety of people during gas fire extinguishing Halon is determined according to the requirements normative documents NPB 88, GOST R 50969, GOST 12.3.046 and is provided by preliminary evacuation of people prior to the supply of fire extinguishing gas according to the signals of the alarms during the designated time delay. The minimum duration of the time delay for evacuation is determined by the airbag 88 and is 10 s.

Isothermal module for liquid carbon dioxide (MIZHU)

MIZHU consists of a horizontal tank for storing CO2, a locking and starting device, devices for monitoring the amount and pressure of CO2, refrigeration units and a control panel. Modules are intended for the protection of premises with a volume of up to 15 thousand m3. Maximum capacity of MIZHU is 25 tons of CO2. The module stores, as a rule, a working and reserve supply of CO2.

An additional advantage of MIZHU is the ability to install it outside the building (under a canopy), which allows you to significantly save production space. In a heated room or in a warm block-box, only MIZHU control devices and UGP switchgears (if any) are installed.

MGP with a capacity of cylinders up to 100 liters, depending on the type of combustible load and the filled GFFS, can protect a room with a volume of no more than 160 m3. To protect larger rooms, the installation of 2 or more modules is required.
A technical and economic comparison showed that it is more expedient to use isothermal modules for liquid carbon dioxide (MIZHU) to protect premises with a volume of more than 1500 m3 in the UGP.

MIZHU is designed for fire protection of premises and technological equipment as part of gas fire extinguishing installations with carbon dioxide and provides:

supply of liquid carbon dioxide (LC) from the MIZHU reservoir through a locking and starting device (ZPU), refueling, refueling and draining (ZhU);

long-term non-drainage storage (LH) in the tank with periodically working refrigeration units(HA) or electric heaters;

control of pressure and mass of ZhU during refueling and operation;

the ability to check and customize safety valves without relieving pressure from the reservoir.

Gas fire extinguishing- This is a type of fire extinguishing, in which gas extinguishing agents (GFFS) are used to extinguish fires and fires. An automatic gas fire extinguishing installation usually consists of cylinders or containers for storing a gas extinguishing agent, gas that is stored in these cylinders (containers) in a compressed or liquefied state, control units, pipelines and nozzles that ensure the delivery and release of gas to the protected room, the device is received -control and fire detectors.

Story

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 installations began to be used in Germany, England and the United States, a significant number of them appeared in the 30s. After the Second World War, installations with the use of isothermal reservoirs for storing CO 2 (the latter were called low pressure carbon dioxide fire extinguishing installations) began to be used abroad.

Halons (halons) are more modern gas extinguishing agents (OTV). Abroad, at the beginning of the 20th century, halon 104, and then in the 30s, halon 1001 (methyl bromide) were used very limitedly for fire extinguishing, mainly in hand-held fire extinguishers. In the 50s in the USA research work which made it possible to propose halon 1301 (trifluorobromomethane) for use in installations.

The first domestic gas fire extinguishing installations (UGP) appeared in the mid-30s to protect ships and vessels. Carbon dioxide was used as a gaseous OTV (GOTV). The first automatic UGP was used in 1939 to protect the turbine generator of a thermal power plant. In 1951-1955. gas fire extinguishing batteries with pneumatic start (BAP) and electric start (BAE) have been developed. A version of the modular design of batteries with the help of type-setting sections of the CH type was used. Since 1970, the batteries have been using the GZSM locking and starting device.

In recent decades, automatic gas fire extinguishing systems have been widely used, using

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

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

Freon 125 is used as a fire extinguishing agent to protect premises without a permanent stay of people.

Carbon dioxide is widely used to protect archives and vaults.

Extinguishing gases

Gases are used as fire extinguishing agents, the list of which is defined in the Code of Practice 5.13130.2009 "Installations fire alarm and automatic fire extinguishing ”(paragraph 8.3.1).

These are the following gas extinguishing agents: freon 23, freon 227ea, 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 ( technical specifications) for a specific object. (Code of rules SP 5.13130.2009 "Automatic fire alarm and fire extinguishing installations" (note to table 8.1).

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

The first group of GOTV is inhibitors (freons). They have an extinguishing mechanism based on chemical

inhibiting (slowing down) the combustion reaction. Getting into the combustion zone, these substances intensively disintegrate

with the formation of free radicals, which react with the primary combustion products.

In this case, the burning rate decreases until it completely dies out.

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

namely, freon 23, freon 125, freon 227ea are ozone non-destructive.

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

Greenhouse gases.

The second group is gases that dilute the atmosphere. These include compressed gases such as argon, nitrogen, inergen.

To keep burning necessary condition is the presence of at least 12% oxygen. The principle of diluting the atmosphere is that when compressed gas (argon, nitrogen, inergen) is introduced in the room, the oxygen content is reduced to less than 12%, that is, conditions are created that do not support combustion.

Liquefied gas extinguishing agents

Liquefied gas freon 23 is used without a propellant.

Freons 125, 227ea, 318Ts to ensure transportation along piping in the protected area require pumping with a propellant gas.

Carbon dioxide

Carbon dioxide is a colorless gas with a density of 1.98 kg / m³, odorless and does not support the combustion of most substances. The mechanism for stopping combustion with carbon dioxide lies in its ability to dilute the concentration of reactants to the limits at which combustion becomes impossible. Carbon dioxide can be discharged into the combustion zone in the form of a snow-like mass, while exerting a cooling effect. From one kilogram of liquid carbon dioxide, 506 liters are formed. gas. The fire extinguishing effect is achieved if the concentration of carbon dioxide is at least 30% by volume. Specific gas consumption in this case will be 0.64 kg / (m³ · s). Requires the use of weighing devices to control the leakage of fire extinguishing agent, usually tensor weighing devices.

Cannot be used to extinguish alkaline earth, alkali metals, some metal hydrides, developed fires of smoldering materials.

Freon 23

Freon 23 (trifluoromethane) is a light, colorless and odorless gas. It is in the liquid phase in the modules. It has a high pressure of its own vapors (48 KgC / sq. Cm), does not require a propellant gas pressurization. Gas leaves the cylinders under the influence of its own vapor pressure. The control of the mass of the GFFS in the cylinder is carried out by the mass control device automatically and continuously, which ensures constant monitoring of the operability of the fire extinguishing system. The fire extinguishing station is capable, at the standard time (up to 10 seconds), to create a standard fire extinguishing concentration in rooms located at a distance of up to 110 meters horizontally and 32 - 37 meters vertically from the modules with GEFU. Distance data is determined using hydraulic calculations. The properties of freon 23 gas make it possible to create fire extinguishing systems 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 extinguishing concentration is 14.6%. Safety margin for people 35.6%. This allows the use of Freon 23 to protect premises with people.

Freon 125

Chemical name - pentafluoroethane, ozone-safe, symbolic designation - R - 125 HP.
- colorless gas, liquefied under pressure; non-flammable and low-toxic.
- designed as a refrigerant and fire extinguishing agent.

Freon 218

Freon 227ea

Freon 227ea is a colorless gas, used as a component of mixed freons, gas dielectric, propellant and fire extinguisher

(foaming and cooling agent). Freon 227ea is ozone-safe, ozone-depleting potential (ODP) - 0 There is an example of the use of this gas in an automatic gas fire extinguishing installation in a server room, in a gas fire extinguishing module MPH65-120-33.

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

They are poured 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. In this case, for each 1 dm 3 of the capacity of the container, no more than 1.1 kg of liquid freon should be filled. Transported by railroad and by road.

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

Freon 318Ts

Freon 318ts (R 318ts, perfluorocyclobutane) Freon 318C - liquefied under pressure, non-flammable, non-explosive. Chemical formula - C 4 F 8 Chemical name: octafluorocyclobutane Physical state: colorless gas with a faint odor Boiling point −6.0 ° C (minus) Melting point −41.4 ° C (minus) Auto-ignition temperature 632 ° C Molecular weight 200.031 Ozone Depletion Potential (ODP) ODP 0 Global Warming Potential GWP 9100 MPC w.w. mg / m3 w.w. 3000 ppm Hazard class 4 Fire hazard characteristic Non-combustible gas. Decomposes on contact with flame producing highly toxic products. There is no flammable area in the air. Decomposes on contact with flames and hot surfaces to form highly toxic products. At high temperature reacts with fluoride. Application Flame arrester, 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 extinguishing agents (Nitrogen, argon, inergen)

Nitrogen

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

Nitrogen cannot 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, much less often helium.

Argon

Inergen

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

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 displacement 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 will go out within 30-45 seconds.
• A distinctive feature of Inergen is its content of 8% carbon dioxide.

Others

Steam can also be used as a fire extinguishing agent, but these systems are mainly used for extinguishing inside technological equipment and in the holds of ships.

Automatic gas fire extinguishing systems

Gas fire extinguishing systems are used in cases where the use of water can cause a short circuit or other damage to equipment - in server rooms, data warehouses, libraries, museums, aircraft.

Automatic gas fire extinguishing installations must provide:

In the protected room, as well as in adjacent ones that have an exit only through the protected room, when the installation is triggered, light devices (a light signal in the form of inscriptions on light boards "Gas - go away!" And "Gas - do not enter!") And sound alerts must be switched on in accordance with GOST 12.3.046 and GOST 12.4.009.

The gas extinguishing system is also included as component in explosion suppression systems, used to phlegmatize explosive mixtures.

Testing of automatic gas fire extinguishing installations

The tests should be carried out:

• before putting the units into operation;
• during the period of operation at least once every 5 years

In addition, the weight of the waste water treatment plant and the pressure of the propellant in each vessel of the installation should be carried out within the time limits established by the technical documentation for the vessels (cylinders, modules).

Tests of installations to check the response time, the duration of the supply of the WWTP and the fire-extinguishing concentration of the WWTP in the volume of the protected premises are not mandatory. The need for their experimental verification is determined by the customer or, in case of deviation from the design standards affecting the parameters being checked, officials of the governing bodies and subdivisions of the State fire service in the implementation of state fire supervision.

Mobile gas fire extinguishing equipment

Fire fighting installation"Shturm" joint production of the Nizhny Tagil OJSC "Uralkriomash", the Moscow experimental design bureau "Granat" and the Yekaterinburg production association "Uraltransmash" extinguishes major fire on a gas well in just 3-5 seconds. This is the result of testing the installation on fires in places of gas fields in the Orenburg and Tyumen regions. So high efficiency is achieved due to the fact that "Shturm" extinguishes the flame not with foam, powder or water, but with liquefied nitrogen, which is thrown into the fire through nozzles installed in a semicircle on a long boom. Nitrogen has a double effect: it completely blocks the access of oxygen and cools the fire source, preventing it from flaring up. Fire at oil and gas facilities sometimes cannot be extinguished by conventional means for months. "Shturm" is made on the basis of a self-propelled artillery installation, which easily overcomes the most difficult obstacles on the way to hard-to-reach sections of gas pipelines and oil wells.

Fluoroketone based gas fire extinguishing

Fluoroketones are a new class of chemicals developed by 3M and introduced into international practice... Fluoroketones are synthetic organic substances in which all hydrogen atoms are replaced by fluorine atoms firmly bound to the carbon skeleton. Such changes make the substance inert from the point of view of interaction with other molecules. Numerous test tests conducted by leading international organizations have shown that fluoroketones are not only excellent fire extinguishing agents (with an efficiency similar to halones), but also demonstrate a positive environmental and toxicological profile.

Head of the design department of Technos-M + LLC SA Sinelnikov

Recently, in the fire safety systems of small objects to be protected by automatic fire extinguishing systems, automatic gas fire extinguishing installations are becoming more widespread.
Their advantage lies in fire-extinguishing compositions that are relatively safe for humans, complete absence of damage to the protected object when the system is triggered, repeated use of equipment and extinguishing the source of fire in hard-to-reach places.
When designing installations, the most common questions arise regarding the choice of fire extinguishing gases and the hydraulic calculation of the installation.

In this article we will try to reveal some aspects of the problem of choosing a fire extinguishing gas. All the gas extinguishing compositions most often used in modern gas fire extinguishing installations can be conditionally divided into three main groups. These are substances of the freon series, carbon dioxide, commonly known as carbon dioxide (CO2), and inert gases and their mixtures.

In accordance with NPB 88-2001 * all these gaseous fire extinguishing agents are used in fire extinguishing installations for extinguishing fires of class A, B, C in accordance with GOST 27331 and electrical equipment with a voltage not higher than that specified in the technical documentation for the used fire extinguishing devices.

Gas OTV are used mainly for volumetric fire extinguishing in the initial stage of a fire in accordance with GOST 12.1.004-91. Also, GFFS are used to phlegmatize an explosive atmosphere in the petrochemical, chemical and other industries. tension.

It is prohibited to use GFFS for extinguishing:

a) fibrous, loose and porous materials capable of spontaneous combustion with subsequent smoldering of the layer inside the volume of the substance (sawdust, rags in bales, cotton, grass flour, etc.);
b) chemicals and their mixtures, polymeric materials prone to smoldering and burning without air access (nitrocellulose, gunpowder, etc.);
c) chemically active metals (sodium, potassium, magnesium, titanium, zirconium, uranium, plutonium, etc.);
d) chemicals capable of undergoing external decomposition (organic peroxides and hydrazine);
e) metal hydrides;
f) pyrophoric materials (white phosphorus, organometallic compounds);
g) oxidants (nitrogen oxides, fluorine)

It is forbidden to extinguish class C fires if, in this case, it is possible to release or enter the protected volume of combustible gases with the subsequent formation of an explosive atmosphere. In the case of using GFFS for fire protection of electrical installations, the dielectric properties of gases should be taken into account: dielectric constant, electrical conductivity, dielectric strength. As a rule, the limiting voltage at which it is possible to carry out extinguishing without turning off the electrical installations by all GEF is no more than 1 kV. To extinguish electrical installations with voltages up to 10 kV, only CO2 of the highest grade in accordance with GOST 8050 can be used.

Depending on the extinguishing mechanism, gas fire extinguishing compositions are divided into two qualification groups:
- inert diluents that reduce the oxygen content in the combustion zone and form an inert environment in it (inert gases - carbon dioxide, nitrogen, helium and argon (types 211451, 211412, 027141, 211481);
- inhibitors that inhibit the combustion process (halocarbons and their mixtures with inert gases - freons)

Depending on the state of aggregation, gas fire extinguishing compositions under storage conditions are divided into two classification groups: gaseous and liquid (liquids and / or liquefied gases and solutions of gases in liquids).
The main criteria for choosing a gas extinguishing agent are:

Human safety;
- Technical and economic indicators;
- Preservation of equipment and materials;
- Restriction on use;
- Impact on the environment;
- Ability to remove GFFS after application.

It is preferable to use gases that:

Possess acceptable toxicity in the used fire-extinguishing concentrations (suitable for breathing and allow personnel to be evacuated even when gas is supplied);
- thermally resistant (form a minimum amount of thermal decomposition products, which are corrosive, irritating to the mucous membrane and poisonous when inhaled);
- most effective in fire extinguishing (they protect the maximum volume when supplied from a module that is filled with gas up to the maximum value);
- economical (provide minimum specific financial costs);
- environmentally friendly (do not have a destructive effect on the ozone layer of the Earth and do not contribute to the creation of the greenhouse effect);
- provide universal methods for filling modules, storing and transporting and refilling.

The most effective in extinguishing a fire are chemical gases called freons. The physicochemical process of their action is based on two factors: chemical inhibition of the oxidation reaction process and a decrease in the concentration of the oxidant (oxygen) in the oxidation zone.
Hladon 125 has undoubted advantages. According to NPB 88-2001 *, the standard fire extinguishing concentration of Hladon 125 for class A2 fires is 9.8% by volume. This concentration of Freon 125 can be increased to 11.5% by volume, while the atmosphere is breathable for 5 minutes.

If we rank GFFS in terms of toxicity in the event of a massive leak, then the least dangerous are compressed gases, since carbon dioxide protects a person from hypoxia.
The freons used in the systems (according to NPB 88-2001 *) are low-toxic and do not show a pronounced pattern of intoxication. In terms of toxicokinetics, freons are similar to inert gases. Only with prolonged inhalation exposure to low concentrations of freons can adversely affect the cardiovascular, central nervous systems, and lungs. With the inhalation of high concentrations of freons, oxygen starvation develops.

Below is a table with the time values ​​of a person's safe stay in the environment of the most commonly used brands of freons in our country at various concentrations.

The use of freons when extinguishing fires is practically safe, since the fire-extinguishing concentrations for freons are an order of magnitude less than lethal concentrations with a duration of exposure up to 4 hours. Approximately 5% of the mass of freon supplied to extinguish the fire undergoes thermal decomposition, therefore the toxicity of the environment formed when extinguishing the fire with freons will be much lower than the toxicity of pyrolysis and decomposition products.

Freon 125 is ozone-safe. In addition, it has maximum thermal stability compared to other freons, the temperature of thermal decomposition of its molecules is more than 900 ° C. The high thermal stability of Freon 125 allows it to be used to extinguish fires of smoldering materials, because at a smoldering temperature (usually about 450 ° C), thermal decomposition practically does not occur.

Freon 227ea is no less safe than freon 125. But their economic performance as part of a fire extinguishing system is inferior to Freon 125, and efficiency (the protected volume from a similar module differs insignificantly). It is inferior to Freon 125 in terms of thermal stability.

The specific costs of CO2 and freon 227ea practically coincide. CO2 is thermally stable when extinguishing fire. But the CO2 efficiency is not high - a similar module with HFC 125 protects the volume 83% more than the CO2 module. The fire-extinguishing concentration of compressed gases is higher than that of freons, therefore, 25-30% more gas is required and, therefore, the number of containers for storing gaseous fire-extinguishing substances increases by a third.

Effective fire extinguishing is achieved at a CO2 concentration of more than 30% vol., But such an atmosphere is unsuitable for breathing.

Carbon dioxide at concentrations of more than 5% (92 g / m3) has a harmful effect on human health, the volume fraction of oxygen in the air decreases, which can cause the phenomenon of oxygen deficiency and suffocation. When the pressure drops to atmospheric pressure, liquid carbon dioxide turns into gas and snow with a temperature of minus 78.5 ° C, which cause frostbite of the skin and damage to the mucous membrane of the eyes. In addition, when using carbon dioxide automatic fire extinguishing systems, the ambient temperature of the working area should not exceed plus 60 ° C.

In addition to freons and CO2, inert gases (nitrogen, argon) and their mixtures are used in gas fire extinguishing installations. The unconditional environmental friendliness and safety for humans of these gases are the undoubted advantages of their use in AUGPT. However, the high fire-extinguishing concentration, and the associated larger (compared to freons) amount of gas required and, accordingly, a larger number of modules for its storage, make such installations more bulky and expensive. In addition, the use of inert gases and their mixtures in AUGPT is associated with the use of a higher pressure in the modules, which makes them less safe during transportation and operation.