No one needs to tell how dangerous any fire is, and how hard it is to fight fire, which is capable of destroying the results of many years of work of human hands together with man himself in a matter of hours. However, it used to be so. However, time passes, and science develops with it. Today, people have learned to fight fire and learn about the threat of a fire at the moment when the flame first appeared, and it is not difficult to cope with it. All this became possible with the advent of such a device as an automatic fire extinguishing installation.
What is this? What are its goals?
Automatic systems and installations for fighting fire, as a rule, are part of a set of devices designed to ensure the overall fire safety of a building or structure. Their main purpose is to prevent the spread of flames and fight against the elements at the earliest stages.
These devices are optionalcomponents of the fire extinguishing system. However, at such facilities where there is an increased threat of fire and rapid spread of flame, as well as where there is no possibility of emergency evacuation of people caught in the fire affected area, automatic fire extinguishing installations (AFS) can be said to be simply irreplaceable.
An automatic fire fighting system can be called a set of devices that can independently activate when parameters and factors controlled in the protected zone are exceeded relative to threshold values.
A distinctive feature of these devices is their performance of automatic fire alarm functions. These elements, usually included in the overall fire fighting system, should ensure the achievement of one, or better, several goals at once, the main of which are:
- elimination of the flame on the protected object until the critical values of ignition factors are reached;
- elimination of fire before the limit of fire resistance of building structures at the facility;
- elimination of the fire earlier than the maximum damage to property and material values will be caused;
- termination of combustion processes before there is a danger of destruction of technological installations with which the protected object is equipped.
Further, among the most important functions that must be performed by automatic fire extinguishing installations, there is such as emergency assistance in providing a safe zone for people on the territoryobject.
Options for existing automatic installations
At the moment, there are quite a few options for automatic installations for fighting fire. They can be classified according to several parameters. By design, these devices can be aggregate, modular, deluge and sprinkler. According to the method of extinguishing the fire, they can be voluminous, by area and local.
According to the method of operation (or start) of the installation, they can be divided into manual, automatic and with various kinds of drives (electric, hydraulic, pneumatic, mechanical, combined).
According to such a factor as inertia, automatic fire extinguishing installations can be divided into ultra-fast, high-speed or small inertia, medium inertia and high.
In addition to the above, fire extinguishing installations are classified according to the duration of the supply of fire extinguishing agent. They can be impulse, short-term, medium-term and long-term.
However, both among specialists and among ordinary consumers, the most famous is the classification according to the type of substance used to extinguish the flame. According to this factor, automatic fire alarm and fire extinguishing installations can be divided into water, foam, gas aerosol, powder and steam.
Foam based installations
Automatic foam fire extinguishing installationis one of the most complex, because it additionally includes mechanisms that convert the powder from a specific composition into foam (they are called sprinklers or steam generators). In addition, in foam installations (in particular, in a fire pipeline), special containers or tanks should be provided in which a concentrate for foam production or an already prepared composition will be stored.
The use of the finished composition and the preparation of foam directly in the process of extinguishing a fire are two incomparably different principles of AUPT operation. Each of these methods has both positive and negative aspects. If we draw a boundary between them purely conditionally, then we can say that an automatic fire extinguishing installation, in which the foam concentrate and the water supply are stored separately, will be more effective in protecting large areas.
Installations with a composition ready for direct use are more suitable for extinguishing flames on objects of small areas, because there are a number of disadvantages that appear when storing large enough volumes of foam mass. Among the most significant are the following. The finished composition has a short shelf life, i.e. it must be changed regularly, which entails an increase in cash costs (moreover, in proportion to the size of the tank). Further, if the required pressure is able to provide fire water supply, then it makes no sense to invest in constructionlarge reservoir. In addition, the contact of the foam composition and concrete is unacceptable, that is, it will be necessary to cover the inner surface of the storage container with epoxy mastics, which, again, increases the cost. And large tanks make it much more difficult to dispose of old foam and replace it with new one.
Automatic foam fire suppression system will be most effective in chemical and petrochemical applications where a lot of flammable liquids are stored. It is also justified to use them in warehouses and in hangars with equipment, that is, where there are usually few people and there is no way to quickly evacuate material assets.
Water installations for fighting fire
Installations that use water in their work are the most versatile compared to all others, since they can be used where the safety of people and the possibility of their emergency evacuation is a priority goal over everyone else (offices, government agencies, etc.).).
Installations that use water to extinguish fires can be divided into two types: local (sprinkler) and protecting the entire building as a whole (drencher).
Automatic sprinkler fire extinguishing installation (from the English sprincle - "drizzle, splash") is equipped with a fully autonomous response system. When a temperature increase is registered at any point of the protected surface, it (UAPT) is activated independently and sends a jet of finely atomized liquid as close as possible to the heat source.
If, when choosing UAPTs, their water type is preferred, you need to pay attention to the type of control unit (“dry” or “wet”). The former are mainly used on unheated objects and premises, while the latter (“wet”) are used where the temperature is never below zero.
Drencher water fire extinguishing installations (automatic), unlike sprinklers, are never autonomous. They always work in tandem with the fire alarm system that activates them. Deluge devices are not equipped with sensors that would determine the location of the source of increased heat separation and coordinate their work in this direction. These units, when operating, cover all accessible surfaces in the protected area with water.
If preference is given to water versions of UAPT, it must be remembered that water can react with some organometallic compounds and compounds. The result of such reactions may be the release of toxic substances into the air, which, of course, will create conditions that prevent the evacuation of people, and may harm their he alth. For this reason, the use of automatic water-type fire extinguishing installations, as a rule, is unacceptable at those industrial-type facilities where coal, iron, metal carbides, etc. are involved in the technological cycles. Also, the desired effect will not be achieved in cases where water be used to extinguish flames in rooms in which flammable liquids with a temperature ofburning not higher than 90 degrees.
TEV settings
At present, a new unique technology for the operation of a water fire extinguishing installation has been developed and successfully implemented. Automatic devices of the new generation do not cover all accessible surfaces with a thin layer of water, but spray the liquid in small droplets directly into the flame. The liquid evaporates, thereby binding the fire. Such means are called water mist fire extinguishing installations (TRV). In addition to binding an open fire, the evaporation of a liquid leads to an increase in vaporization. Steam, in turn, reduces the volume of free oxygen contained in the closed space and thereby suppresses the possibility of combustion processes. The result of the impact of such installations is the maximum localization of the fire, its separation and complete extinction of the flame.
Automatic fire extinguishing systems using fine atomization technology work effectively in places where flammable compounds and liquids are stored. Also, such AUPTs are able to stop the combustion process, provoked by sudden voltage drops in the mains. In such cases, most often you have to fight fire when extinguishing electrical equipment that is under voltage. Provided that the water sprayer and the burning object are at a distance of at least 1 m, the permissible voltage values \u200b\u200bcan reach up to 36000 V.
In addition, a cloud of tiny water droplets is an excellent absorbent that binds carbon monoxide vapor, ash and other particles that can cause serious damage to organshuman breath. The process of extinguishing a fire with an expansion valve does not prevent the evacuation of people (if necessary) and the protection of property.
Of the minuses of such devices is the inability to use them in places where there is a risk of contact with organometallic compounds.
Gas type units
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In the premises protected by gas AUPT, upon the occurrence of the fact of operation, devices and mechanisms of light (the inscriptions "Gas - go away!" and "Gas - do not enter!") And sound notification of a fire should be turned on. These are the requirements of the GOST system.
Gas fire extinguishing installations (automatic) create an environment where the development of fire is impossible in principle. This is very convenient for rooms with a high risk of flame spread. If the fire area is small and the introduction of significant volumes of gas is not required, such fire extinguishing is possible even without preliminary evacuation of people. However, you need to know that gas in large doses can cause serious damage to human he alth.
The use of gas installations for extinguishing fires is justified in cases of fire in power supply premises, at thermal power plants and state district power plants (extinguishing generators in the case of using hydrogen-type cooling), at facilities forin the production of flammable materials, in long-distance transport, in warehouses with valuables. In libraries and museums, such installations can be used provided that exhibits and rarities are stored under glass.
It should be remembered that a gas-based automatic fire extinguishing installation will not be effective where materials can burn without the participation of oxygen in this process. Such devices are also not used in cases where materials are prone to spontaneous combustion and smoldering (wood chips, rubber, cotton, etc.), for certain types of metals that can react with gases, for pyrophoric materials.
Powder fire extinguishing systems
At present, most often (about 80% of cases), all previously described types of automatic fire extinguishing installations are inferior to powder-type UAPs. This breadth of application is due to a number of advantages. Firstly, these devices are quite versatile (it is possible to use them even for extinguishing electrical installations). Secondly, the shelf life of the reagent is quite long, and its disposal is not very difficult. In addition, these UARTs have a high temperature limit and are non-toxic.
Powder-type units are capable of fighting class A, B and C fires, which significantly expands their capabilities in extinguishing fires at remote sites, where sometimes you have to wait a long time for help.
An automatic fire extinguishing installation using powders is effective in case of fires at oil loading and pumping facilities, when working with electrical points andnodes. However, the desired result will not be achieved if materials are burning that do not need oxygen to support this process, as well as those that are prone to spontaneous combustion and smoldering.
Powder extinguishing devices are not compatible with smoke ventilation systems. And since the latter must be present where people are constantly located, then industrial facilities, warehouses and tunnels fall on the share of powder UAPT.
Aerosol type devices
Automatic aerosol fire extinguishing installation is a rather highly specialized device. They cannot be used to extinguish fires of potentially explosive substances, as well as where people are constantly present. The composition of the aerosol itself is, in principle, harmless and is not capable of causing any serious harm to he alth. However, by operating autonomously, automatic fire alarms and aerosol fire suppression systems prevent people from seeing where escape routes are.
Due to the high efficiency of these UAFs, people can wait in the building until it is completely eliminated. But here it is important to follow and take the necessary measures in order to prevent the explosion of the installations themselves due to the large amplitude of fluctuations in internal pressure relative to external temperatures.
Aerosol-type devices have proven themselves in cases where it was necessary to extinguish fires caused by power outages. Effectivesuch installations and in the fight against fires of technogenic origin. It is an ideal fire safety tool for large vehicles, oil farms, etc.
However, such an automatic fire extinguishing and alarm system using aerosols is not able to completely eliminate smoldering in the inner layers (porous, fibrous materials) and combustion without the presence of oxygen.
Autonomous actuation and action settings
Above in the text, in most cases, automatic stationary fire extinguishing installations were described, but along with them there is the concept of an autonomous system for fighting a fire. What is it?
Autonomous installation is capable of independently detecting a source of increased heat transfer and making a decision on the need to activate the fire extinguishing process. Such devices can be fully attributed to water and gas UAPT. Such systems, as a rule, are equipped with special sensors that are sensitive to temperature rise or identify the corresponding particles in the air composition. If such factors are fixed, the sensors transmit a signal to their own panel for analysis and commands to activate the workflow (in case of a clear fire threat). For different types of installations, the sequence of actions may differ slightly, however, in most cases, the algorithm is constant: "identification - request - activation".
So, the mandatory components included in the autonomousautomatic fire extinguishing installations are devices for detecting and starting and, in fact, devices for direct fire extinguishing. The former, of course, can be called the most important node of an autonomous installation. Detection and triggering devices include fire detectors equipped with a battery or generating EMF using an induction coil. Other devices include fire cord, thermal lock and initiating powder.
In addition, autonomous installations often have the ability to manually start the system, which allows you to activate the workflow without waiting for the moment when the temperature in the protected area exceeds critical values. This function is very, very useful, since a person can often feel and react to the signs of a developing fire (temperature increase, smell, smoke, etc.) much earlier than the mechanical sensor system does.
Price range
When installing automatic fixed fire extinguishing systems to protect your own households, it is important to strike a balance, not trying to save where it is unacceptable, but not investing extra money, since a fire is a rare phenomenon, and the maintenance of a fire extinguishing installation is financially comparable to its original cost.
Today, powder and aerosol type UAPs are considered the cheapest, since they cause irreparable damage to material values and, for the most part, are dangerous for plants and animals. Gas installations are slightly more expensive: there is no harm to property, butthe tightness of the premises and the preliminary evacuation of people are required. Foam plants are even more expensive, but generally not applicable in private housing construction and are ideal for warehouses and hangars with equipment.
The most expensive systems can be called fine water spray systems, which in no way interfere with the evacuation of people, allow you to wait out the fire in the room until it is completely eliminated and do not cause any harm to material values. The liquid droplets are so small that when they come into contact with the flame, they evaporate without reaching the surfaces. Also, during the fire extinguishing process, steam is generated, which prevents the spread of fire and lowers the temperature in the room.
