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Ins and outs of aerosol fire extinguishing systems, all in this article

November 6, 2022

Aerosol Fire Extinguishing System is widely used in variety of industries now, and now it can be compared with the traditional gas type suppression systems, why aerosol is so awesome? today, let’s talk about it.

ORIGIN AND DEVELOPMENT HISTORY OF AEROSOL FIRE EXTINGUISHING SYSTEM

Aerosol fire extinguishing technology is developed from the military technology of the former Soviet Union. It has a history of more than 50 years; In Russia, it has formed a series of products, which are widely used in various places to extinguish fires.

In 1990’s it was subsequently applied by high-tech companies in the United States, Italy, The Netherlands, Cyprus and Malaysia, Their purpose is mainly for fire-fighting.

In the year 2002, it became imported to China, our company and another company Shanxi JR and China national Institute and University together import the aerosol suppression technology from Russia, after many years of development, we published the newest aerosol technology based on a more clean aerosol agent and more advanced activation elements.

We have studied and analyzed the following development processes of aerosols, and the details are as follows:

FIRST GENERATION-SMOKE EXTINGUISHING TECHNOLOGY

First generation aerosol fire extinguishing technology originates from the former Soviet Union, they use it to launch rockets, many year later, some Russian fire suppression enterprises found that aerosol also can be used for fire-fighting, so one of them invented an aerosol fire extinguishing device.

The smoke fire extinguishing system belongs to the pipe network fire extinguishing technology, the fire extinguishing mechanism is mainly like this: The fire extinguishing agent in bulk is ignited in a spiral way by the fuse wrapped on the ignition cylinder, the fire extinguishing agent produced by the initial burning agent and the generating agent without burning reaction are sprayed to the burning area with high pressure, it covers the flames by means of total submergence, asphyxiates by inert gas, decomposes and cools the solid particles to achieve the goal of extinguishing fire.

The problem existing in the improvement of fire extinguishing technology are as follow: the fire extinguishing compound is divided into bulk agent, which burns violently, has large instantaneous pressure, and has the risk of losing control; the device is not equipped with a cooling system, which makes a great risk.

SECOND GENERATION-POTASSIUM NITRATE(ALSO NAMED K TYPE) AEROSOL EXTINGUISHING TECHNOLOGY

Second generation potassium nitrate aerosol fire extinguishing technology is also called K type technology, wherein, K means the element symbol of potassium, it is the second stage of aerosol fire extinguishing technology during its development.

It starts from the explosion suppression system of armored vehicles of the former Soviet Union in the Middle 1960’s. The technical features of this stage are: It mainly uses potassium nitrate as the main oxidant, many countries in the world have carried out in-depth research and improvement on this technology, and invented many medicines and products in different forms. Beijing University of Technology introduced this technology into China and applied it to the full submergence fire fighting in the enclosed space.

Although potassium nitrate aerosol fire extinguishing technology was developed in the Middle of 1960’s, however, the secondary fire hazards caused by high temperature during reaction and aerosol release of this type of aerosol extinguishing agent could not be effectively solved at that time, and it has a congenital fatal defect-It will cause secondary damage to precision instruments and high technology of equipment, cultural relics, archives etc, the root cause is that the chemical substances produced by the combustion of potassium nitrate are corrosive, some American and European aerosol technology suppression system adopt this technology to produce aerosol suppression device.

THIRD GENERATION-STRONTIUM NITRATE(S TYPE) AEROSOL SUPPRESSION TECHNOLOGY

Since the signing of the Montreal Agreement, more and more people have realized that halon products have great destructive power to the atmospheric ozone-layer, the living environment of human beings is under great threat.

Aerosol fire extinguishing technology is gradually recognized and valued by people as a green and environmental friendly halon alternative, However, the defects of K type aerosol need to be improved.

In 2002, the scientific research team led by SHANXI JR and our company, found that a new combination of strontium nitrate as the main oxidant and potassium nitrate as the auxiliary oxidant is used in the aerosol generator formula, which can greatly reduce the secondary damage to electronic equipment while ensuring the fire extinguishing ability.

After two years of continuous exploration, the proportion of strontium nitrate was gradually determined, and finally the type S hot aerosol fie extinguishing agent was successfully developed, which fundamentally solved the secondary damage problems in insulation, corrosion and other aspects of the protected object.

In 2004, the national Fire Protection Bureau of China prepared the standard specification GA499.1-hot aerosol fire extinguishing systems to define the relevant technical indicators of type S; in 2005, it incorporated aerosols into the gas fire extinguishing systems and prepared standard-GB50370 code for Design of gas fire extinguishing systems, which clarified that S type aerosol generator could be used in electronic equipment rooms and other places instead of halon agents; After the revision of the standard, type s aerosol fire extinguishing devices have been widely used in mobile base stations, railway signal rooms and other places.

WHAT IS AEROSOL AND WHY IT CAN EXTINGUISH FIRE

Aerosol is a colloidal system formed by suspension of liquid or solid particles in a gas dispersion medium, the use of aerosols as fire extinguishing agent is an important role in practical applications, Its dispersion is composed of liquid, solid or solid-liquid mixture.

Aerosol fire extinguishing agent can be divided into two types: one is the process in which the gas dispersion medium and the dispersed medium are stable before the aerosol extinguishing agent is released, and the gas dispersion liquid or solid extinguishing agent forms aerosol; The other is that the release of aerosol extinguishing agent undergoes combustion reaction, the reaction product contains both solid and gas. The gas dispersed solid particles form aerosols, which can also be called aerosol generators.

According to the temperature at which aerosols are produced, they can be divided into cold aerosols and hot aerosols, when the reaction temperature is higher than 300℃, it is called hot aerosol; when the reaction temperature is lower than 300℃, it is called cold aerosol.

Aerosol extinguishing agent is generally composed of oxidant, reducing agent, performance additive and adhesive.

Aerosol generating agent is an energetic material, belonging to pyrotechnic composition. Its selection, manufacture, performance parameters and processing technology are all guided by pyrotechnics.

To reduce the temperature at which aerosols are produced, there are two ways to use coolant. One is to evenly mix the coolant in the agent, which is called internal cooling; Another cooling method is to place the coolant in the gas path of the gas generator, which can be called external cooling. The general practice is to use the external cooling method.

The aerosol fire extinguishing device is generally composed of shell, ignition device, aerosol agent, coolant, spacer ring, nozzle and other accessories, In particular, the agent contains a variety of chemical components that can extinguish the fire. The main extinguishing substances are strontium nitrate and potassium nitrate, Its starting methods are generally electric starting, thermal starting and manual starting. In practical applications, most of them are electric starting and thermal starting; When the aerosol generator is started, it will extinguish the fire with extremely high speed and efficiency, and extinguish the flame in a few seconds.

WHAT IS EXTINGUISHING PRINCIPLE OF AEROSOL FIRE EXTINGUISHING AGENT

Mechanism of heat absorption, temperature reduction to suppress fire

K2O will decompose when the temperature is higher than 350℃, the melting point of K2CO3 is 891℃, the solid particles in the aerosols are mainly K2O, K2CO3 and KHCO3 etc, Which will have a strong endothermic reaction on the flame, the heat released by any fire is limited in a short period of time. If the solid particles in the aerosol can absorb part of the heat of flame in a short time, the temperature of the flame will be reduced, and the heat radiated to the burning surface of the combustibles for gasification of combustibles and decomposition of the vaporized combustibles into free radicals will be reduced, and the speed of combustion reaction will be restrained to a certain extent, this effect is especially obvious in the early stage of fire.

is limited in a short period of time. If the solid particles in the aerosol can absorb part of the heat of the flame in a short period of time, the temperature of the flame will be reduced, and the heat radiated to the burning surface of the combustibles for gasification of combustibles and decomposition of the vaporized combustibles into free radicals will be reduced, and the speed of combustion reaction will be restrained to a certain extent, This effect is especially obvious in the early stage of fire.

Mechanism of gaseous phrase chemical suppression

  • Gas phase chemical inhibition.
    Under thermal action, K dissociated from the solid particles in the aerosol may exist in the form of steam or cation, and it may have multiple chain reactions with the active groups H, OH and O during combustion in a moment: K+OH?KOH; K+O?KO; KOH+OH?KO+H2O;KOH+H?K+H2O; Consume the exothermic reaction between active groups and inhabit the exothermic reaction between active groups H, OH, O, thus inhibiting the combustion reaction.
  • Solid phase chemical inhibition.
    The solid particles in the aerosol are very small, with the particle size between 10-9 m and 10-6 m, with large specific surface area and surface energy, it is a typical thermodynamic unstable system. It has a strong tendency to lower its surface energy in order to reach a relatively stable state.

Therefore, it can selectively adsorb some charged ions, so that the unsatisfied force field on its surface can be compensated to reach a relatively stable state; Although these particles are small, they are much larger than the size of free groups and pyrolysis products of combustibles, and have considerable adsorption capacity for active free groups and pyrolysis products of combustibles.

It can make the pyrolysis products of combustibles no longer participate in the reaction of generating active free radicals, which will reduce the source of free radicals, thus inhibiting the combustion rate.

In a world, aerosols produce a series of chain reactions, consume a large number of active genes, and interrupt the combustion chain, below is the aerosol chain reaction and its fire extinguishing schematic diagram:

MAIN APPLICATION OF AEROSOL GENERATOR

It has been proved by history and practice tat it can be used in various industries and places.

If classified by fire type, it can extinguish the following types of fire:

  • Solid combustible material fire, for example: paper, wood, textiles.
  • Flammable fires, for example: Petrol, Diesel, Oil.
  • Electrical fires, for example: Natural gas, Propane.
  • Electrical fires, for example: Short circuiting equipment.
  • Cooking Oil and fats fire, for example: deep fat fryers.

If classified by industry application, it can be used in the following industries, but not limits to:

  • Logistic and warehousing.
  • Manufacture and Processing.
  • Food and beverage.
  • Marine and voyage.
  • Telecommunication.
  • Chemicals.
  • Mining industry.
  • Sports and Culture.
  • Education and health care.
  • Energy and energy storage.
  • Municipal facilities.
  • Road traffic and transportation.
  • Residential and commercial construction etc.

If classified by specific application program, it can be use in the following places, but not limits to:

  • Computer room.
  • Server room.
  • Cable well and cable trench.
  • Data processing room.
  • Switch gear.
  • Substation.
  • Transformer.
  • Operating floor.
  • Wind turbine.
  • Power facility.
  • Auto vehicles.
  • Power cabinet.
  • Control box.
  • Battery cabinet.
  • Distribution board.
  • Agricultural machinery.
  • Construction machinery.
  • Mining equipment and facilities.

But it can not be able to use in the following places:

a. Places full of people or public places.

b. Places where the following substances are stored:

  • Substances that can be oxidized without air, such as Nitrocellulose and gunpowder.
  • Active metal, such as potassium, sodium, magnesium, titanium etc.
  • Metal hydride, such as potassium fluoride, sodium hydride.
  • Self-decomposing chemicals, such as some peroxides, hydrazine.
  • Spontaneously combustible substance, such as phosphorus.
  • Strong oxidants, such as nitrogen oxide and fluorine.

AEROSOL FIRE EXTINGUISHER FEATURES ADVANTAGES AND DISADVANTAGES

ADVANTAGES OF AEROSOL SYSTEM

Aerosol have the following benefits and advantages that we count out:

  • Small in dimension or size, it is space saving.
  • Compact and highly concentrated, its design density only 60 to 100 grams per cubic meters.
  • Non toxic, non corrosive, no residual powder after spraying, so it is environmentally friendly, green and healthy.
  • It is paced with high-grade metal materials, without any pressure, it is a safe product.
  • According to the aging test, its service life can be arrives at 10 to 15 years, in which other fire extinguishing agents can be up to 5 years only.
  • It spray evenly, and instantly extinguish the fire point.
  • It is easy to install with a bracket or 3M glue. It is maintenance free and can be used like a household appliance.
  • It can be started without electricity, which means that it can automatically detect and thermal start, with very powerful functions.
  • It is stored as a solid and not easy to volatilize, so there will be no leakage and other problems.

DISADVANTAGES OF AEROSOL SYSTEM

  • The temperature is very high when it is sprayed, so it may hurt people if someone touches or approaches.
  • The fire extinguishing efficiency is very high when it is used in a closed or semi closed place. But if it is used in an open area, the fire extinguishing efficiency may be slightly lower.

HOW TO CALCULATE USAGE AND WHAT IS ITS FORMULA

It is designed according to the Chinese Aerosol Fire Extinguishing System Design Code GA499.1-2010, which is copy from and refer to standards of NFPA2010, UL2775 and ISO15779, in China its design formula as below:

M=Da*Fa*V

M is the aerosol quality, normally in kilograms, Da is the aerosol design concentration, unit in kg/m3, Fa is additional design factors, also named “correction factor”, V is the protection space volume.

For example, a electrical cabinet is with space of 2 meter length, 1.5 meter width, 1 meter height, then the total volume is 3 m3, as the Da is normally 0.1 (Kilograms/m3), and Fa is 1.0 (under the condition that the space is not over 500 m3), so based on these data, we can calculate out that M=2*1.5*0.1=0.3 kilograms, this means a 300 gram of aerosol generator is required to install in this electrical cabinet, for total flooding purpose.

HOW TO INSTALL AND MAINTAIN AEROSOL 

Because aerosol is a system without pressure and pipe network, so its installation and maintenance are very simple.

Firstly, Install with supporting bracket, clamp and screw; Among them, small aerosols can also be installed with 3M adhesive tape, and floor standing aerosols can be directly placed on the floor to install.

Secondly, Aerosol agent is a very stable chemical substance, non volatile and non pressure, so it does not require annual maintenance by staff.

But it needs to be replaced after 10 years service life since from its manufacturing date.

ATTENTION MATTER OF AEROSOL DEVICE

The following items shall be noted during aerosol installation and commissioning:

a. The aerosol fire extinguishing device should not be installed in the following positions:

  • Escape route.
  • Near the open fire and fire source.
  • Places easy to be drenched, watered or flooded.
  • Places frequently subject to vibration, impact and corrosion.
  • Near air inlet, air outlet, door, window and other openings.

b. Key points of aerosol installation:

  • It is forbidden to dismantle the aerosol device without authorization.
  • The installation is not affected by the height of the position. It can be placed on the ground, on the wall or on the ceiling.
  • Select the applicable model according to the installation conditions in different places.
  • There should be no obstacles within and around one meter in front of the installation location.
  • No other objects are allowed to be placed on the aerosol fire extinguishing device.
  • When debugging the system, use the relay, or the ignition head/thermo bulb for debugging, do not directly connect the aerosol device, because it will spraying agent after the power is on.

If there are other questions that need us to answer, please consult our customer service team info@aerosol.com.

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