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What is aerosol fire extinguisher? One article takes you to understand
1. What is Aerosol fire extinguishing
2. Aerosol fire extinguisher development history
The first generation of aerosol fire extinguishing technology was born in our country, also known as smoke fire extinguishing technology, which began in the early 1960s. It was completed by scientific researchers from the Tianjin Fire Research Institute of Public Security, who independently developed an automatic smoke fire extinguishing system, which is mainly used to extinguish fires in Class A, B, and C liquid storage tanks.
In the early 1980s, with the emergence of environmental protection problems of “halon fire extinguishing agent”, finding alternatives to halon became an important research topic.
At the end of the 1980s, Russian scientists first succeeded in researching aerosol fire extinguishing technology that can extinguish fires in a submerged manner, which opened up a new way for halon substitution research. Subsequently, aerosol fire extinguishing technology has attracted the attention of the international community, and countries such as China, the United States, Australia, Malaysia and other countries have also begun research on new aerosol fire extinguishing technologies.
Generally speaking, aerosol is a stable state system formed by the dispersion of fine solid or liquid particles in a gas. Professionally, it refers to a colloidal system that uses gas (usually air) as the dispersion medium and solid or liquid particles as the dispersant.Common aerosols in nature—clouds, smoke, fog, etc.The size of the particles in aerosols is mostly in the order of 10-5 to 10-1μm, which has gas fluidity and can diffuse around obstacles.
The medicament in the aerosol fire suppression system device is solid, and the component emitted by the medicament through the oxidation-reduction reaction is aerosol. The first generation of aerosol fire extinguishing technology-smoke fire extinguishing technology.
K-type aerosol fire extinguisher, also called potassium salt fire extinguishing technology, is the second stage of the development of aerosol fire extinguishing technology, which began in the former Soviet Union in the mid-1960s. Our country started late in this regard, starting in the early 1990s.
In this type of aerosol generating agent, potassium nitrate is mainly used as the main oxidant. Its sprays have high fire extinguishing efficiency, but because they contain a large amount of potassium ions, Easy to absorb moisture, forming a yellow and sticky strong alkaline conductive liquid film, this substance is very damaging to electronic equipment, so K-type aerosol automatic fire extinguishing device can not be used in electronic equipment, precision instruments and cultural relics Archive place. At present, the use in the market is gradually decreasing.
The third-generation aerosol (S type) is mainly made of strontium salt as the main oxidant. Unlike the second-generation potassium salt (K-type) aerosol, strontium ions do not absorb moisture, do not form a conductive solution, and will not cause damage to electrical equipment. In 2001, China Mobile Communications Corporation selected the strontium salt aerosol (S-type aerosol automatic fire extinguishing device) produced by the company after strict inspection and verification to protect its communication base stations and other places equipped with sophisticated electronic equipment.
At present, strontium salt aerosol products have been applied in thousands of engineering projects, and the third-generation aerosol has become more and more accepted by users
3. Aerosol fire extinguisher application range
a. Electrical fire
Communication room, communication base station, electronic computer room, etc.;
Electrical fires in places containing precision instruments and equipment, such as power distribution rooms, generator rooms, cable interlayers, cable wells, cable trenches, etc.
b. Solid surface fire
Surface fire of combustible solid materials in places where combustible solid materials are used or stored.
c. Liquid fire
Liquid fires in places where diesel oil is produced, used or stored (except -35 diesel), heavy oil, transformer oil, animal and vegetable oil and other flammable liquids of Category C; Before extinguishing a gas fire, the gas source can be cut off.
d. The S-type aerosol fire extinguishing device cannot be used to put out the following fires
①Substances that can be oxidized without air, such as nitrocellulose, gunpowder, etc.; active metals, such as potassium, sodium, magnesium, titanium, etc.; compounds that can decompose by themselves, such as certain peroxides, hydrazine, etc. Metal hydrides, such as potassium fluoride, sodium hydride, etc. Natural substances, such as phosphorus. Strong oxidants, such as nitrogen oxide, fluorine, etc.
② Deep fire of combustible solid materials.
③Fire in crowded places, such as theaters, auditoriums, etc.
④ Fire in places with explosion hazard, such as workshops with explosive dust.
⑤ Ultra-clean environment, such as pharmaceutical workshops, chip processing places, medical rooms, etc.
4. Aerosol fire extinguishing working principle
The four elements of combustion: combustibles, oxidizer, temperature and uninhibited chain reaction. The fire extinguishing mechanism of fire extinguishing gas is to eliminate one or several of the four elements of combustion.
The solid fire extinguishing agent in the S-type aerosol fire extinguishing device is started by electricity, and it undergoes redox reaction to form a large number of agglomerated fire extinguishing aerosols, and its composition is mainly N2, a small amount of CO2, and metal salt solid particles.
Aerosol fire extinguishing mechanism is as follows
Mechanism of endothermic cooling and fire extinguishing
Metal salt particles absorb a large amount of heat at high temperatures, and undergo physical endothermic processes such as thermal melting and gasification. The flame temperature is lowered and then radiated to the combustible combustion surface for gasification of combustible molecules and vaporized combustible molecules. The heat of pyrolysis of combustion molecules into free radicals will decrease, and the combustion reaction speed will be suppressed to a certain extent.
① Gas phase chemical inhibition: Under the action of heat, the vaporized metal ions or electron-losing cations decomposed in the fire extinguishing aerosol can interact with the active groups in the combustion, repeatedly consume a large amount of active groups, and reduce burning free radicals. .
② Solid-phase chemical suppression: The particle size of the fire extinguishing aerosol is very small (10-9～10-6m), has a large surface area and surface energy, can adsorb the active groups in the combustion, and produce chemical effects. Consume a lot of active groups and reduce burning free radicals.
③ Reduce oxygen concentration: N2 and CO2 in fire extinguishing aerosol can reduce the oxygen concentration in combustion, but its speed is slow, and the fire extinguishing effect is far less than heat absorption and temperature reduction and chemical inhibition.
5. Aerosol fire extinguisher advantages and disadvantages
Advantages of aerosol fire suppression system
No harm to human body, high fire extinguishing efficiency, less fire extinguisher consumption, weight and space saving, environmentally friendly, easy installation, extremely low maintenance cost, and cost saving.
The small aerosol fire extinguisher belongs to the total submerged system. Under the condition of controlling the fire source, the full submerged fire extinguishing is gradually completed, so that people have enough time to evacuate and escape.
It is suitable for power distribution rooms, generator rooms, energy storage, battery boxes, cable trenches, etc People, relatively closed, and small spaces are suitable for extinguishing fires caused by the production and storage of diesel (except -35 diesel), heavy oil, lubricating oil and other Class C combustible liquids and surface fires of combustible solid materials.
The aerosol is stored in a solid form, and it is not volatile, so there will be no leakage and other problems, it has a long storage life, and the facilities in the protected area can also be easily monitored from time to time.
Disadvantages of aerosol fire suppression system
The aerosol fire suppression system used in indoor places or enclosed space or semi-enclosed space, because the aerosol spray happens very quickly and if outdoors, it will not reach the necessary concentration to put out the fires.
The S type aerosol fire suppression system is disposable, charging one time but last 10 years life time.
6. Aerosol fire suppression system design & calculation
China aerosol fire suppression system is calculated by Chinese Standard GA499.1-2010, which the china standard is similar with NFPA2010, UL2775, ISO15276, but china have its own calculation formula.
The calculation formula are as below:
W=C2 * KV * V
Here by W is aerosol quality in kg, C2 is design application density in kg/m³.
And in design it is normally use design density of 100 gram cover per 1 cubic meter, for example, a 100 gram of china strontium nitrate aerosol compound cover 1 cubic meter space, 250 gram cover 2.5 cubic meter, and so on.
The aerosol agent and its components are together gathered into a 304 stainless steel or red painted steel cylinder, the cylinder is set with extinguishing nozzles for let aerosol discharging out when it works, also in installation is use installation brackets and screws, or mount by magnetic and 3M brand of glue.
7. Aerosol fire suppression system vs fm200
We know that FM200 gas suppression system is the world’s most famous fire suppression system, some people want to compare aerosol with fm200, now hereby we help to compare with you, their differences are below:
1. Aerosol agent is normally solid compound and hfc-227ea agent is liquid when store in cylinder.
2. Aerosol is without pressure and no need pressurized cylinder to load, and hfc-227ea is have pressure need pressurized cylinder to load.
3. Aerosol is non toxicity but hfc-2227ea will have a little toxicity.
4. Aerosol start-up have 4 ways of electrical activation, thermal cord, thermo bulb, liner heat detector activation; FM200 device is with N2 or Electronic start-up.
5. Aerosol device is work without pipeline, but normally FM200 system need piping, special steel cylinder, pressure cylinder and valves to work.
6. Aerosol device not have problem of leakage, but FM200 may have problem of leakage.
7. Aerosol device is easy to install, low cost in maintenance, instead FM200 system maybe more complex.
8. ALT value of aerosol is zero and GWP value of aerosol is zero, but ALT value of FM200 is 31 years and GWP value of FM200 is 2050.
Their commons points are below:
1. Low in ODP value.
2. Both fire extinguishing ability and fire extinguishing speed are high and fast.
3. Both belongs to gas suppression system.
Vehicle engine aerosol fire suppression system
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