I. AUTOMATIC FIRE ALARM SYSTEM OVERVIEW
Automatic fire alarm system is a system that can detect and alarm whenever a fire occurs. The system operates continuously in 24/24 hours and can detect fire automatically by fire detectors or by people.
II. AUTOMATIC FIRE ALARM’S COMPONENTS
A typical automatic fire alarm system includes 3 following components:
1- Fire alarm center
Designed in cabinet style, contain main equipments: mainboard, adapter and battery
2- Input equipments
- Detector: smoke detector, heat detector, gas sensor, fire.
- Emergency switch (emergency button)
3. Output equipments:
- Display panel (keypad).
- Alarm sounder, siren.
- Strobe light, Emergency light
- Interactive phone module.
III. FIRE ALARM SYSTEM’S PRINCIPLE OPERATION
Fire alarm system operates in a closed process. When input equipments (detector, emergency button) detect fire signals (temperature increases suddenly, smoke or spark appears), they will send information about the fire to the center. At the system center, fire alarm panel processes the the received information and send signal to output equipments (display panel, alarm sounder, siren, alarm light), these equipments will announce people about the fire by light or sound.
IV. TYPE OF FIRE ALARM SYSTEM
Fire alarm system uses two kinds of power voltage: 12V and 24V
In theory, both voltages have the same usage. Compared to 24V fire alarm system, 12V fire alarm system is not as professional, its center is mostly used in intrusion alarm, and the system has to have programming keypad. While 24V fire alarm system is a professional fire alarm system, which can transmit signal over longer distance, and may operate without programming keypad. However, 12V fire alarm system’s processing panel is cheaper than 24V fire alarm system.
Besides, fire alarm systems are also classified into 2 main types:
1- Common fire alarm system:
With simple functions, low cost, common fire alarm system is suitable for small and medium-sized area (about several thousand m2), with little number of rooms; or small house and shop… All the system’s equipments are connected together and to the center panel in series. When a problem occurs, the center will know the alarm zone (not be able to specify the exact place). This will limit the operator’s actions.
2- Addressable Fire Alarm System
With the most advanced technology, addressable fire alarm system is the most ideal for large scale or multi-area application where area is separately splitted. All the equipments are connected directly to the center panel to receive the fire signal from each area, each site. Then the center can know the information about the fire accurately and completely. Information will be displayed on the display panel for the operator to settle the problem quickly and safely.
V. EQUIPMENT’S DETAILED INFORMATION
1- Fire Alarm Panel:
The fire alarm panel is the most important and critical component of the fire alarm system. It receives and processes the fire signal or failure signal, display information about the system, place of the fire or alarm, it also supplies the power for the detectors. When necessary, the fire alarm panel can send signal to the associate person or system. In addition, the center panel has the ability to check the system operation’s condition or find the reason of the system’s failure.
2- Input equipments:
The input equipments that is sensitive to the phenomenon of fire (temperature increment, smoke, photogenic, luminescence,…) will receive the information about the place of fire and send the signal to the fire alarm panel.
2.1.1 Smoke Detector:
- The smoke detector, the direct sensor, detects the occurrence of smoke to inform the center. The time of detecting smoke and sending the signal to center is only 30s. The normal smoke density of environment is from 15% to 20%. If the environment’s smoke density exceed the limit (10%-20%), the equipments will send the alarm signal to the center.
- Smoke detectors are normally installed in office, conference room. vault, and in place where has close space and substances that creates smoke first.
- Smoke detector is divided into 2 main types:
22.214.171.124 Spot-type smoke detector:
Being used in small area, with low ceiling (office, apartment…), spot-type smoke detector includes two kinds
a. Ionization type smoke detector: Detector generates streams of moving minus and positive ions. When smoke occurs, it will block the movement of ions, then the detector will send the fire alarm signal to the center.
b. Photoelectric smoke detector: The detector includes a pair of poles (a transmitter and receiver) set in two opposite sides. When smoke occur between the two poles, smoke will block the transmitting line of the two poles, then the detector sends the alarm signal to the center
126.96.36.199 Beam smoke detector:
- Beam smoke detector includes a pair of devices installed at two sides of the monitored place. One device is the transmitter that creates a infrared beam. The other is the receiver that receives the beam from the transmitter. The receiver has a photoelectric sensor to monitor the balance of the beam. The principle operation of the detector is blurring contrary light by light diffusing principle.
Beam smoke detector has very long range (15m x 100m), suitable for used at place where photoelectric smoke detector can’t be used, for example in place where fire creates black smoke first.
In addition, beam smoke detector can operate in severe weather conditions i.e. high or low temperature, dust, high humidity,…Since beam smoke detector can be placed after glass for easy cleaning and maintenance.
Beam smoke detector is used in large area where the ceiling is too high to install spot type detector (workshops,…)
2.1.2 Heat Detector:
- Heat detector is the detector that monitor the environment’s temperature. When the temperature does not meet the pre-defined regulations of the detector, it will send the alarm signal to the center.
- Heat detector is used in applications that can’t used smoke detector (machine storey, garage, high voltage electrical cabinet, factory, kitchen,…)
188.8.131.52 Fixed temperature heat detector
Fixed temperature heat detector is actived and send the alarm signal when the temperature increases to the pre-defined temperature. (57o, 70o, 100o…)
184.108.40.206 Rate of rise heat detector
Rate of rise heat detector is actived and send the alarm signal when the temperature increases 9oC per minutes
2.1.3 Gas Detector
- Gas detector is the detector used for monitor and alarm when the gas density is over 0.503% (Propane/ Butane).
- Gas detector is usually installed near places that have gas such as gas storage tank… Gas detector is fixed on wall, 10-16cm from the floor, it must not fixed on the floor.
2.1.4 Flame Detector
- Flame detector is used to sense the ultraviolet beam from fire, and send alarm signal to the center.
- Flame detector is usually used at places that have extremely high risk, or places where the light of fire is the typical sign (i.e. flammable liquid tank).
- Flame detector is very sensitive to ultraviolet beams and is reliable to avoid false alarm. The detector only sends alarm signal when there is two ultraviolet sensing pulses in every 5s.
2.2- Emergency Breaker
Emergency Breaker is installed at conspicuous place of corridor or stair for prompt action when needed. This equipment is used to send the alarm signal for warning people about the fire to evacuate and handle the fire. Emergency breaker has many type:
2.2.1 Round or square type
2.2.2 Break glass
2.2.3 Pull type
3- Output equipments:
The output equipments receive signal from the fire alarm panel and inform the information by sound (bell, horn), light (strobe light) to let people know that there is a fire.
3.1 Display panel
The display panel is used to display information about the fire zone. The status signal is sent from the fire alarm panel.
3.2 Alarm bell
Installed at the security room, corridor, stairs or crowded place, the alarm bell alarms everybody about the fire.
When an alarm occurs, the alarm bell will sound to help the security guards know about the detailed alarm information through display panel.
3.3 Alarm horn
The alarm horn has the same features and mounting place as the alarm bell, and is specially used where the distance is too far.
3.4 Alarm Light
Alarm lights have many type, each type has different usage and mounting place.
3.4.1 Exit Light
Mounted near stairs, exit light indicates the emergency exit in case of fire. Automatically lighting when the AC power is lost.
3.4.2 Corridor Lamp
Installed beside the emergency breaker. Corridor lamp will light when the emergency breaker is activated. It is also emergency light for people in the house. This is very important since the still-working emergency breaker need to be distinguished from the malfunction one in case of fire.
3.4.3 Room Lamp
Installed at the door of room, room lamp helps to identify the problem room.
3.4.4 Emergency Light:
When a fire occurs, the power will be cut off. In that case, the emergency light will be turned on automatically to help people to find emergency exit easily or help the responsible persons to do the needing. In case the power is cut off, the emergency light is also a temporary light.
3.5 Interactive phone module
Installed in the central cabinet, when receiving the fire alarm signal from the panel, this equipment will dial to predefined phone number to inform the responsible people. The interactive phone module probably has the ability to dial to 3-10 phone numbers.
Keypad is the equipment used for controlling the system operation. Through keypad, you can easily control the operation as your wish, such as enter the command to switch the system to monitoring mode, stop monitoring some zones, or program for scheduling the system to monitor some zones.
3.7 Address module:
Addressable module is used in addressable fire alarm system, this equipments helps to identify the accurate location of the fire.
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