【 Weak current College 】 on automatic fire alarm and fire control system design and equipment selection (1)---Power By 【 China power house network 】

Abstract: the automatic fire alarm and fire control system design and equipment selection is one of the electrical design. This article is in the design of some of the problems in practice, such as automatic fire alarm and fire control system, select, and so on.

Keywords: fire auto-alarm fire control system for electrical design

A modern building with large scale, high standards, personnel are crowded, the device numerous, extremely stringent fire safety requirements. To this end, in addition to building layout, construction and decoration materials selection, equipment selection and configuration has a lot of restrictions, you also need to set up a modern fire-fighting facilities. As China's economic construction, high-rise buildings, large and medium-sized commercial building, plant emergence, automatic fire alarm system raised higher and more stringent requirements. For early detection and notification of a fire, preventing and reducing the fire hazard, the protection of personal and property safety, defend socialist modernization in the modernization of industrial civil buildings, hotel, library, research and business sectors, automatic fire alarm system has become an essential facility. Electrical engineering design, installation and use are correct not only directly affects the building fire safety but also directly related to the various fire facilities can truly make a difference. Therefore, automatic alarm and fire protection design and equipment selection is very important.

1. system composition

Automatic fire alarm and fire control system is the building fire safety integrated monitoring system, fire alarm systems and fire control system. In a real application, the system consists of a wide range of how many of the devices, device classes are very different. However, the decision system features an automatic fire alarm and fire control system.

(A) automatic fire alarm system

Automatic fire alarm system typically consists of a detector and signal line and automatic alarm device made up of three parts.

1, fire detectors and alarm button

Fire detectors are entire alarm system testing component. Its stability, reliability and sensitivity, and other specifications directly affects the entire operation of fire protection systems.

1) detector types

Fire detectors are many kinds of generally are the following:

(1) Ion sensing smoke detectors.

(2) photoelectric smoke detector.

(3) thermal detectors (including fixed temperature and temperature-difference).

(4) gas-detector.

(5) IR-detectors.

(6) UV-detector.

2) common basic principles of fire detectors

(1) smoke detector

Fire development process can be classified in the early phases, stages of development and decay is off stage. Smoke detector features in the initial phase of combustion smoke, can automatically issue a fire alarm signal, with a view to put out the fire before without a disaster. According to the structure, a smoke detector can be divided into ion sensing smoke detectors and optical smoke detector.

① ion sensing smoke detector

Ion sensing smoke detector is composed of two series of sources containing Am241 room, FET and switch circuit. Ionization chamber that compensation within the Chamber is sealed, a smoking is not easy to enter; ionization chamber that is outside the examination room, is the opening of the tobacco successfully entered. In-line two ends of the ionization chamber directly access 24V DC power supply. When a fire occurs, smoke entered the test ionization chamber, of α-Ray Am241 blocked, reducing their ability, and ionization ionization current reduction, test ionization chamber air equivalent impedance and compensation ionization chamber for smoke-free access, the impedance of the ionization chamber remains unchanged, so that applied to two ionization chamber ends divider ratio changes in test ionization chamber for both sides voltage increase volume reaches a certain value, the switch circuit actions, issue a warning signal.

② photoelectric smoke detector

Photoelectric smoke detector consists of a light source, optoelectronic components and electronic switches. Use of light-scattering theory on fire smoke for the early detection and timely alarm signal. According to the different light sources can be divided into general optical, laser and optical, ultraviolet photoelectric 4 infrared photoelectric, etc.

A general photoelectric smoke detector, based on their structural characteristics can be divided into shading-and scattering of two kinds.

Shading type photoelectric smoke detector consists of a lamp (bulb or light-emitting diode) and a corresponding optoelectronic components in a small dark room. In smoke-free, light sources emit light through the lens and the light beam, exposure to electro-optical components, and convert them into electrical signals, so that the whole circuit is maintained in the normal state, not beep. When the fire had a smoke into the detector so that the light propagation characteristics change, light intensity significantly weakened, circuit normal state is destroyed, the alarm signal.

Scattering photoelectric smoke detector of light-emitting diode and the optical component of the location is not set. Optoelectronic components set in porous small darkroom. No smoke, light not hoses and optoelectronic components, circuit to maintain normal state. But there is a fire, smoke detectors, light entering through the smoke particles of reflection or scattering to da optoelectronic components, optical signal conversion to electrical signals, amplified by the amplifier circuit, driven automatic alarm beep signal.

B, laser-smoke detector. The laser transmitter (including pulse power and laser generator) and laser receiver (including optical receivers, pulse amplification and alarm). It utilizes strong laser orientation, high brightness and color and coherence of good features. In no case, pulsed laser beam shoots to the photodiode, conversion to electrical signals, alarm beep. Once the laser beam in emission during smog shielding and weakened to a certain extent, the photodiode signal noticeably, detectors issue reportAlarm signal. In a wide range of laser source, a semiconductor laser with low excitation voltage required, high efficiency, pulse power, device volume is small, seismic resistance, long life and low-cost advantages and attention.

C, ultraviolet and infrared light smoke detector. They have a high sensitivity, stable performance, reliable, accurate detection of orientation, etc., and generally pay attention to, and become important equipment of fire detectors and development direction.

Photoelectric smoke detector developed rapidly, the species is increasing, their function is concerned, it can achieve early fire alarm, in addition to the large interior, but also especially suitable for the electrical fire hazard in larger establishments, such as the computer room, instrumentation, and trenches, tunnels and so on.

(2) heat fire detectors

Heat detector principle different in terms of structure with double metal film chip-type, box type, heat-sensitive electronic components and three.

① bi-metal blade-type is application of two different expansion coefficients of metal as a sensitive element, generally made of poor modest fixed temperature in two forms, fixed temperature is increased when the ambient temperature reaches the set temperature, constant temperature parts immediate action, the alarm signal; differential temperature is rising sharply when the ambient temperature, the temperature rise rate (¡æ/min) meet or exceed the requirements of action temperature detector rate, poor temperature parts immediate action, the alarm signal.

② membrane cartridge-type detector consists of corrugated plate form a gas chamber, indoor air only via gas plug screw holes and atmosphere. Under normal circumstances (of environment temperature rise rate not greater than 1 ℃/min), Chamber heated, indoor expansion of gas through gas plug screw holes leakage into the atmosphere. In the event of fire, the temperature rise rate increased sharply, increasing the pressure of the gas chamber, corrugated plate up muster, promotion of elastic contact, through to the electrical contacts, the alarm signal.

③ Electronic heat detector consists of two resistance and temperature characteristics of the same thermistor and electronic switch line, one in a thermistor can directly experience the environment temperature, and the other closed to a certain heat capacity of the ball. When the outside temperature is changing slowly, two thermistor resistance with temperature change basic close, switch circuit not actions. When the fire broke out, the ambient temperature rises dramatically, two thermistor resistance changes, the original state of sabotage switch circuit open, an alarm signal.

3) fire detector options

(1) according to the characteristics of fire detector selection

① in the early stages of a smoldering fires, resulting in a lot of smoke and a small amount of heat, of little or no flame, should use smoke detector.

② fire rapidly, produce a lot of heat, smoke and flame radiation, can choose smoke detector and heat detector, flame detector or their combination.

③ fire rapidly, there is a strong fire radiation and a small amount of smoke and heat, should use flame detector.

④ fire formation of unpredictable and can carry out simulation test, according to test results select probes.

(2) according to the installation site environment feature selection detector

① long-term relative humidity greater than 95%, airflow speed greater than 5m/s, have large amounts of dust, water spray stranded, potentially corrosive gases, under normal circumstances where there's smoke, stranded, produce alcohols, ethers, ketones, and other organic substances in place, it is not advisable to use ion sensing smoke detectors.

② may generate a smoldering fire not early or alarm will cause major loss of place, it is not advisable to use thermal detectors; temperature is 0 degrees centigrade of places, it is not advisable to use fixed temperature probes; under normal conditions of temperature changes, should not use differential temperature detector.

③ a place, it is not advisable to use flame detector:

A, no fireworks disaster that may occur;

B, the flame spread of smoke front has occurred;

C, detectors of lens susceptible to pollution;

D, probes the ' eye ' susceptible to blocking;

E, detector easy Sun or other sources of direct or indirect irradiation;

F, under normal circumstances, have open fire jobs as well as the x-ray, arc etc.

High-rise buildings and its related parts of fire detector type select the reference in the following table.
Project settings for a site, the type of fire detector is poor temperature differential fixed temperature type constant temperature smoke-I-II-III-class I-II-III-class I-II-III-class I-II-III-1 Theater, cinema, Hall, Conference Hall, Department stores, shopping malls, hotels, hotels, halls, apartments, houses, hospitals, libraries, museums □ 0000 □ □ □ 2000 × 2000, boiler room, 2 kitchens, boiling water disinfection, × × × × × × □ ○ ○ × × × 3 drying drying place × × × × × × □ ○ ○ × × × 4 has the potential to produce large amounts of steam site × × × × × × □ ○ ○ × × × 5 generator room, garage, hangar, × 2000 × 2000 × × × □ ○ 6 TV Studio, film review rooms × × • × □ ○ ○ ○ ○ × 2000 7 fire, the temperature changes very slowly booth × × × ○ ○ ○ ○ ○ ○ □ ○ ○ 8 staircases and inclined road × × × × × × × × × □ ○ ○ aisles and channel 9 × × × × × × × × × □ ○ ○ 10 cable shaft, pipeline well × × × × × × × × × □ ○ ○ 11 electronic computer room, the communications room □ × × • × × • × × □ 0000 12 stacks, underground warehouse □ ○ ○ □ ○ ○ ○ × × □ ○ ○ 13 smoking room, small meeting room × × ○ ○ ○ ○ ○ × × × × ○ ○ said:; □ represents is suitable for use under such conditions, the installation site is limited to the ability to effectively detect fire place; × means no is suitable for use. (3) according to the room height select probes the use of different types of probes and the room height of references in the table below.
Room height (m) smoke detector heat detector flame detector I-II-III-12 & lT; h ≤ 20. unsuitable for unsuitable for 8 < h ≤ 12 suited not ideal for unsuitable for 6 < h ≤ 8 fit suitable for unsuitable for 4 < h ≤ 6 fit suitable for unsuitable for h ≤ 4 suit fit suitable for detector sensitivity option, should as far as performance and use of the probe, under normal circumstances (no fire) false alarm system did not prevail. At present, domestic high-rise buildings, most of the use of photoelectric smoke measurement device, only the individual places, the kitchen, the generator room, garage and a gas fire extinguishing installations of establishments using thermal detectors. Only one detector, linkage system easy to produce malfunction, this will result in the unnecessary loss, no linkage system vulnerable to false positives. It should use two or more types of detectors. They are "and" logical relationships, when two or more probes at the alarm linkage until the action, in order to ensure that unnecessary losses in short, the detector selection should be based on actual environmental situation select suitable detector, to achieve timely, accurate alarm purposes. 4) Manual alarm button alarm area each fire partitions should at least set a manual fire alarm button, and from one fire partitions in any location to the nearest one manual fire alarm button should not be greater than the distance 30m and should be set in clear and easy-to-use location. Manual alarm button from the ground 1.5m. 2, automatic alarm for China's automatic fire alarm equipment, production and application, although relatively late, but the development is very fast, especially in recent years, with the rapid development of China's modernization and strengthening of the fire service, fire alarm installations for the production and use has a larger development, manufacturers, product range and production and application of units are constantly increasing. Our current production of automatic fire alarm device is including alarm display, fault display and control directives issued by the complete automation. When it receives a fire detectors, alarm buttons or other triggers a signal sent to the fire, can emit sound and light alarm signal, to record time, automatic print fire occurrence, location, and output control other fire equipment instruction signal, automatic fire extinguishing system. Currently, the production, use of the automatic warning devices, the use of multiple lines system, divided into area alarm controller, centralized alarm controller and intelligent fire alarm controller. (1) area alarm controller zone alarm is an electronic composition of auto alarm and surveillance devices. It joins a range of all fire detectors, accurate and timely for the automatic fire alarm. Therefore, each zone alarm and the jurisdiction of the fire detectors having properly connected, it cannot constitute a complete and independent automatic fire alarm system. The basic principles of regional alarm: ① receive detector or alarm button issued fire signal to the form of sound and light alarm; ② electronic clock can remember the first time a fire; ③ can lead some to relay contact gives appropriate external function; you can configure an alternate ④ to DC power when the power outage, DC standby power is automatically input; ⑤ with self-test function, when the zone alarm and detectors are bad or broken lines, alarm issued open circuit or short circuit fault sound, light and alarm signal and automatically display faults areas; ⑥ has priority "fire" features all kinds of alarm signal to the regional alarm choose the signal processing circuit, fire, short circuit, open circuit judge, alarm fire alarm signal first issued, indicating the specific fire ignition parts, fire alarm sound, memory, open circuit, short circuit fault signal; ⑦ through communication interface circuit will be three types of signals to set alarm controller. Area alarm controller receives the signals of the fire detectors "and" "or" logical combination control relay use linkage to external devices, such as exhaust valves, air valves, fire doors, etc. At present domestic producers in the capacity of regional alarm that monitor how different parts of the body. Different models of regional alarm with different models of the detector. Xi'an 262 factory JB-QB-2700/088A series range alarm, for example, it has two kinds of wall-mounted, Cabinet type, maximum size is 256 road, is a part number, a detector occupies a position number. In engineering design, select the area alarm controller capacity should be greater than the number of probes in the region. If a building with one floor at a district, a total of 24 rooms, each room a probe, a total of 24 months, you should choose 30 Road area alarm controller. If 48 bedrooms, you should choose 50 loop area alarm controller. (2) centralized alarm controller set alarm controller's basic principle is as follows: ① put several regional alarm connected to form a system of centralized management; ② can poll connected regional alarm have no fire signal or fault signal, and timely indication of fire district parts and fault zone, at the made sound, light and alarm signal; ③ other features, the tenets of area alarm controller. In the system as only detector and centralized alarm is not working. Because the scan function set alarm, fire alarm, self-inspection function are constituted with regional alarm system before. Therefore, the only area of the alarm and set the alarm, in order to constitute an automatic fire alarm system. Set alarm system for large, complex projects. Set alarms maximum capacity received 40 regional alarm. (3) intelligent fire alarm control intelligent fire alarm controller's basic principle is as follows: ① adopt analog detectors, outside non-fire factors, such as temperature, humidity and dust, and so affect the implementation of automatic compensation, resulting in a variety of different conditions to address has a false positive and accurate warning laid the technical foundation; ② alarm controller uses the entire bus computer communication technology, the realization of bus alarm and bus linkage control, reduces the control output and executive bodies of long distance pipeline between; ③ adopt big capacity control matrix and cross-lookup program package, the software programming instead of hardware combinations, and increases the flexibility of the fire and modifiability. 262 factory NA1000 series fire alarm controller in relation to such forms. (4) automatic warning device select the automatic fire alarm system, the fire alarm system should have theThe following basic functions: ① power supply for fire detectors; ② can receive from fire detector or alarm button alarm signal; ③ can detect and send the fault signal system itself; ④ can check fire alarm in the alarm function; ⑤ with power conversion function. Fire alarm controller options, consider the following factors: ① fire detectors, fire alarms to choose the same manufacturers of complementary products; ② alarm system circuit number; ③ need automatic fire control function; ④ installation location and installation methods. (Ii) fire control system of fire control range according to the actual size of the project, the level of the different levels vary. Linkage control equipment with water fire extinguishing, fire hydrant, fire-extinguishing, fire doors, fire shutter, exhaust fan, air-conditioning facilities, fire damper, exhaust valve, elevators, Induction lamp, incident light, alarm, cut off the power supply, etc.