The fire alarm system is divided into the following components
1. Fire detection equipment (detectors) 2. Fire alarm equipment (flashers, sirens, etc.) 3. Cables 4. The central control panel that is in charge of communication between detectors and fire alarm devices. Below is a description of the various components Fire alarm system We pay:
1. Fire detection equipment (detectors)
Detectors are electronic devices that are produced in different shapes and designs and usually white in color by manufacturers and are installed in suitable places in the building such as kitchens, engine rooms, archive rooms, corridors, home rooms and conference rooms on ceilings or walls on special mounting bases. they turn The duty of detectors is to detect fire and report it to the central control panel. Detectors are often powered with a voltage of 15 to 30 volts. There are also detectors that are powered by 12 and 48 V DC or 220 V AC. Usually, there is a warning lamp (LED) on the detectors, which is off in normal mode or blinks intermittently by the central control panel, but after the detector is triggered, it turns on steadily and stays on until the fire effect has not disappeared. Detectors, according to which fire effect they use for detection, are made in different types as follows:
a) Smoke Detector:
These detectors are installed on the ceiling and have a chamber that is triggered after being filled with smoke and when the current changes, they report a fire to the central control panel, and they have three types:
First type: Ionization smoke detector:
These detectors have radioactive elements. As a result of radioactive rays passing through the air inside the chamber and ionizing it, some current passes. When smoke enters this chamber, the flow changes and causes a fire alarm. Due to high sensitivity to smoke, these detectors are used in places where there is a lot of fire and little smoke. A sign is engraved on these detectors that means the presence of radioactive radiation.
Second type: optical smoke detector:
In these detectors, the smoke produced by the fire enters the chamber and affects the light intensity that passes through the detector case. Also, smoke can cause light scattering and reflection. As a result, the light cell that is inside the detector is stimulated by the decrease of light and gives a fire alarm. These types of detectors are also called photoelectric detectors. This type of detector is suitable for places such as plastic warehouses where thick smoke is produced during a fire and the fire burns slowly.
The third type: beam smoke detector (Detector Beam):
In cases where we want to cover a large, open or high place (such as religious places, warehouse, museum and historical buildings, customs, large reception hall, factory hall, sports hall, etc.) and installing normal detectors are difficult or uneconomical, these types of detectors are used. These detectors have an infrared light transmitter (TX) that sends a ray to the receiver (RX) and are installed on two sides of the hall. This receiver device takes the infrared light sent by the transmitter and compares the emission percentage and the light absorption percentage. If the percentage of radiation that is absorbed is low (according to the setting, for example, less than 60%), this state is considered as a sign of the presence of smoke and causes a fire alarm. One example of these detectors is able to cover a space 15 meters wide and 10 to 100 meters long. Their installation height is between 2.7 meters and 25 meters. Their working voltage is 24 V DC.
b) Heat Detector:
This detector has a thermal resistance that changes due to the heat generated by the fire and causes an increase in current and reports the fire to the central control panel. The sensitivity of thermal detectors is lower than other types of detectors, for example, the flame must reach one third of the height of the ceiling for this detector to work. Therefore, they should not be used in places where a weak fire causes a lot of damage. They are also installed on the ceiling and are offered in two types:
First type: fixed thermal detector (FIX):
This detector is triggered at a certain temperature (for example, 55 degrees Celsius), but it does not react to the normal increase in air temperature caused by heating systems, sunlight, etc. Therefore, they are also called fixed or spot thermal detectors. These types of detectors are used in places where sudden temperature changes occur (such as the kitchen).
The second type: rise of rate thermal detector:
This detector is used to compare the amount of temperature increase and display the reaction to it, and it is used in places where the temperature increase occurs gradually (such as the engine room). This type of detector is equipped with a volume to regulate the temperature. Newly built electronic detectors can be used both as a fixed thermal detector and as an increasing detector, and they are called combined detectors, and they have a higher detection power than the above two types. Detectors have also been made that include two floors, one works like a thermal detector and the other works like a smoke detector, and they are used in places like archive rooms and libraries, where both smoke and heat can be generated during a fire. These types of detectors are called multifunctional or multi.
c) Flame detector (Violet Ultra Flame Detector or Flame Infrared):
This detector detects a flame or an infrared ray by using an ultraviolet ray detector and announces a fire. Its response time is about a few seconds and it detects fire very quickly. This device is available in two types that can be installed for indoor and outdoor space. These detectors must be installed in line of sight of the area they will cover. Flame detectors are often used to cover large open spaces with very high ceilings or no smoke collecting roof. The analog detector is a more complete type of these detectors that reacts to flames that even have smoke.
d) Gas Detector:
This detector is used to detect gas leaks and to announce the danger before a fire occurs in places where there are flammable gases. This detector is installed on the wall or ceiling and often has a self-contained alarm and is powered by a battery or 220 volt voltage. Some types of these detectors are able to command a gas valve and close the gas path if a gas leak is detected.
2. Fire alarm equipment
In order to inform the residents of the building about the occurrence of fire, special fire alarm system equipment is used, which are mentioned below:
a: (Sounder):
Sirens are audio news devices that sound when there is a fire. Their construction is usually electronic. Sirens should be heard from all parts of the building. They are installed on the wall. Along with some sirens, a flasher light is installed so that if the environment is noisy, that light will inform people about the occurrence of fire. The power supply of sirens is usually 24 volts DC and the color of sirens is red. In noisy environments, such as workshops and industrial environments, motorized sirens that produce a strong sound are used.
b: (Bell):
In addition to sirens, bells are also used in fire alarm systems.
c: indicator lights:
In spaces where there is a lot of noise, or places where residents cannot hear the sound of sirens, it is necessary to install flashing lights that can be seen from a distance. The types of these lights are as follows: a) Elite strobe light ) These lights are made with constant or flashing light, as well as fixed or rotating, and are usually red and installed on the stairwells or in the corridors. They are closed in parallel with the sirens and are used together with the siren. These lights may also indicate exit routes with the words “Exit” written on them.
d: Fire alarm system manuals (Manual Call Point):
These hands are made for manual fire alarm. In normal mode, the thumb contact is open, and in the fire alarm mode, a resistor in series with the thumb (the value of which is 470 ohms according to the standard) is placed in the path in parallel with the resistance at the end of the line, and the current increases, and as a result, the central control panel of the fire alarm does The word Fire is written on the hands and it is red in color. There are two types of these washers: First type: glass type. In the glass washer type, the washer is under pressure and when the glass is broken, the contact is closed. In these shasti, there is no need to break the glass with a hammer, but the glass should be broken by pressure and the shasti is activated. Second type: Push type In the push type, you have to press the thumb to close the contact. Article related to cables and central control panel (click)