các hệ thống báo cháy của Hochiki, honeywell đầy đủ hướng dẫn Hochiki’s stateofthart FireNET® Vapor detectors include a widerange of air sampling smoke detection systems, from an aspirated pointinabox (PIAB) detector to a unique 15channel addressable detector.
Fire Detection and Alarm System Basics Hochiki America Corporation 7051 Village Drive, Suite 100 Buena Park, California 90621 www.hochiki.com Fire Detection and Alarm Systems A key aspect of fire protection is to identify a developing fire emergency in a timely manner, and to alert the building's occupants and fire emergency organizations This is the role of fire detection and alarm systems Depending on the anticipated fire scenario, building and use type, number and type of occupants and criticality of contents and mission, these systems can provide several main functions: First, they provide a means to identify a developing fire through either manual or automatic methods Second, they alert building occupants to a fire condition and the need to evacuate Another common function is the transmission of an alarm notification signal to the fire department or other emergency response organization They may also shut down electrical, air handling equipment or special process operations, and they may be used to initiate automatic suppression systems Fire Detection Principles Manual Fire Detection - Pull Stations Manual fire detection is the oldest method of detection In the simplest form, a person yelling can provide fire warning In buildings, however, a person's voice may not always transmit throughout the structure For this reason, manual alarm stations are installed The general design philosophy is to place stations within reach along paths of escape It is for this reason that they can usually be found near exit doors in corridors and large rooms The advantage of manual alarm stations is that, upon discovering the fire, they provide occupants with a readily identifiable means to activate the building fire alarm system The alarm system can then serve in lieu of the shouting person's voice They are simple devices, and can be highly reliable when the building is occupied The key disadvantage of manual stations is that they will not work when the building is unoccupied They may also be used for malicious alarm activations Nonetheless, they are an important component in any fire alarm system 2007 NFPA 72, 3.3.63.3 Manual Fire Alarm Box A manually operated device used to initiate an alarm signal Fire Detection Principles Automatic Detectors – Spot type 2007 NFPA 72, 3.3.43.21 Spot Type Detector A device in which the detecting Element is concentrated at a particular location Typical examples are Bimetallic detectors, fusible alloy detectors, certain pneumatic rate-of-rise Detectors, certain smoke detectors, and thermoelectric detectors Fire Detection Principles Automatic Detectors – Photoelectric Hochiki SLR-24V detector 2007 NFPA 72, 3.3.181.4 Light Scattering Smoke Detection The principle of using a light source and a photosensitive sensor arranged so that the rays from the light source not normally fall onto the photosensitive sensor When smoke particles inter the light path, some of the light is scattered by reflection and refraction onto the sensor The light signal is processed and used to convey an alarm condition when it meets preset criteria Fire Detection Principles Automatic Detectors – Photoelectric In the normal case, the light from the light source on the left shoots straight across and misses the sensor When smoke enters the chamber, however, the smoke particles scatter the light and some amount of light hits the sensor A – Light Source B – Photo Sensor Fire Detection Principles Automatic Detectors – Ionization Ionization smoke detectors use an ionization chamber and a source of ionizing radiation to detect smoke This type of smoke detector is more common because it is inexpensive and better at detecting the smaller amounts of smoke produced by flaming fires Inside the ionization detector is a small amount (perhaps 1/5000th of a gram) of Americium241 The radioactive element americium has a half-life of 432 years, and is a good source of alpha particles An ionization chamber is very simple It consists of two plates with a voltage across them, along with a radioactive source of ionizing radiation Hochiki SIJ-24 detector 2007 NFPA 72, 3.3.181.2 Ionization Smoke Detection The principle of using a small amount of radioactive material to ionize the air between two differentially charged electrodes to sense the presence of smoke particles Smoke Particles entering the ionization volume decrease the conductance of the air by reducing ion mobility The reduced conductance signal is processed and used to convey an alarm condition when it meets preset criteria Fire Detection Principles Automatic Detectors – Ionization Ionization Smoke detectors The alpha particles generated by the americium have the following property: They ionize the oxygen and nitrogen atoms of the air in the chamber To "ionize" means to "knock an electron off of." When you knock an electron off of an atom, you end up with a free electron (with a negative charge) and an atom missing one electron (with a positive charge) The negative electron is attracted to the plate with a positive voltage, and the positive atom is attracted to the plate with a negative voltage (opposites attract, just like with magnets) The electronics in the smoke detector sense the small amount of electrical current that these electrons and ions moving toward the plates represent When smoke enters the ionization chamber, it disrupts this current the smoke particles attach to the ions and neutralize them The smoke detector senses the drop in current between the plates and sets off the horn Fire Detection Principles Automatic Detectors – Heat/Thermal Heat detectors are the oldest type of automatic fire detection device They began development of automatic sprinklers in the 1860s and have continued to the present with proliferation of various types of devices Heat detectors that only initiate an alarm and have no extinguishing function are still in use Although they have the lowest false alarm rate of all automatic fire detector devices, they also are the slowest in fire detecting A heat detector is best situated for fire detection in a small confined space where rapidly building high-output fires are expected, in areas where ambient conditions would not allow the use of other fire detection devices, or when speed of detection is not a prime consideration Heat detectors are generally located on or near the ceiling and respond to the convected thermal energy of a fire They respond either when the detecting element reaches a predetermined fixed temperature or to a specified rate of temperature change In general, heat detectors are designed to operate when heat causes a prescribed change in a physical or electrical property of a material or gas 2007 NFPA 72, 3.3.43.9 Heat Detector A fire detector that detects either abnormally high temperature, or rate of temperature rise, or both Heat detectors can be sub-divided by their operating principles : Fire Detection Principles Automatic Detectors – Fixed Temp Fixed-temperature heat detectors are designed to alarm when the temperature of the operating elements reaches a specific point The air temperature at the time of alarm is usually considerably higher than the rated temperature because it takes time for the air to raise the temperature of the operating element to its set point This condition is called thermal lag Fixed-temperature heat detectors are available to cover a wide range of operating temperatures - from about 135'F (57'C) and higher Higher temperatures detectors are also necessary so that detection can be provided in areas normally subject to high ambient temperatures, or in areas zoned so that only detectors in the immediate fire area operate Hochiki DFE Series Heat Detector 2007 NFPA 72, 3.3.43.7 Fixed-Temperature Detector A device that responds when its operating element becomes heated to a predetermined level Non-digital Loop Response When an alarm occurs on many non-digital protocol systems, some panels must continue polling until it reaches the alarming device, before an alarm is initiated Larger systems with hundreds of points can cause delays initiating an alarm Non-Digital Loop Response Addressable Heat Detector Addressable Smoke Detector 001 002 Addressable Input Module (Waterflow) 004 Addressable Pull Station FIRE FIRE SILENT KNIGHT 005 003 Addressable Relay Module (Fan Shutdown) ABC FIRE SYSTEMS ALL SYSTEMS NORMAL 15-Jan-00 3:10 PM Addressable Smoke Detector 006 Non-Digital Loop Response Addressable Heat Detector Addressable Smoke Detector 001 002 Addressable Input Module (Waterflow) 004 Addressable Pull Station FIRE Addressable Smoke Detector FIRE SILENT KNIGHT 006 005 FIRE! 003 Addressable Relay Module (Fan Shutdown) ABC FIRE SYSTEMS ALL SYSTEMS NORMAL 15-Jan-00 3:10 PM A fire erupts at the Heat Detector (Point 001) while the system is polling the Smoke Detector (Point 002) Non-Digital Loop Response Addressable Heat Detector Addressable Smoke Detector 001 002 Addressable Input Module (Waterflow) 004 Addressable Pull Station FIRE Addressable Smoke Detector FIRE SILENT KNIGHT 006 005 FIRE! 003 Addressable Relay Module (Fan Shutdown) ABC FIRE SYSTEMS ALL SYSTEMS NORMAL 15-Jan-00 3:10 PM An alarm is not initiated The system continues polling until it reaches the point in alarm Non-Digital Loop Response Addressable Heat Detector Addressable Smoke Detector 001 002 Addressable Input Module (Waterflow) 004 Addressable Pull Station FIRE Addressable Smoke Detector FIRE SILENT KNIGHT 006 005 FIRE! 003 Addressable Relay Module (Fan Shutdown) ABC FIRE SYSTEMS ALL SYSTEMS NORMAL 15-Jan-00 3:10 PM An alarm is not initiated The system continues polling until it reaches the point in alarm Non-Digital Loop Response Addressable Heat Detector Addressable Smoke Detector 001 002 Addressable Input Module (Waterflow) 004 Addressable Pull Station FIRE Addressable Smoke Detector FIRE SILENT KNIGHT 006 005 FIRE! 003 Addressable Relay Module (Fan Shutdown) ABC FIRE SYSTEMS ALL SYSTEMS NORMAL 15-Jan-00 3:10 PM An alarm is not initiated The system continues polling until it reaches the point in alarm Non-Digital Loop Response Addressable Heat Detector Addressable Smoke Detector 001 002 Addressable Input Module (Waterflow) 004 Addressable Pull Station FIRE Addressable Smoke Detector FIRE SILENT KNIGHT 006 005 FIRE! 003 Addressable Relay Module (Fan Shutdown) ABC FIRE SYSTEMS ALL SYSTEMS NORMAL 15-Jan-00 3:10 PM An alarm is not initiated The system continues polling until it reaches the point in alarm Non-Digital Loop Response Addressable Heat Detector Addressable Smoke Detector 001 002 Addressable Input Module (Waterflow) 004 Addressable Pull Station FIRE Addressable Smoke Detector FIRE SILENT KNIGHT 006 005 FIRE! 003 Addressable Relay Module (Fan Shutdown) ALARM POINT 001 HEAT DETECTOR 15-Jan-00 3:10 PM ALARM! Non-Digital Loop Response Addressable Heat Detector Addressable Smoke Detector 001 002 Addressable Input Module (Waterflow) 004 Addressable Pull Station FIRE Addressable Smoke Detector FIRE SILENT KNIGHT 006 005 FIRE! 003 Addressable Relay Module (Fan Shutdown) ALARM POINT 001 HEAT DETECTOR 15-Jan-00 3:10 PM Systems with hundreds of points can take 15 -20 seconds or longer to respond to alarm conditions Digital Loop Response When an alarm occurs on most digital protocol systems, an interrupt request from the device sensing the alarm interrupts the polling sequence to immediately handle the alarm Systems with hundreds of points will respond to alarms in the same amount of time that they would to smaller systems with very few points Digital Loop Response Addressable Heat Sensor Addressable Smoke Sensor 001 002 Addressable Input Module (Waterflow) Addressable Pull Station 004 006 005 003 Addressable Relay Module (Fan Shutdown) ABC FIRE SYSTEMS ALL SYSTEMS NORMAL 15-Jan-00 3:10 PM Addressable Smoke Sensor Digital Loop Response Addressable Heat Sensor Addressable Smoke Sensor 001 002 Addressable Input Module (Waterflow) Addressable Pull Station 004 Addressable Smoke Sensor 006 005 FIRE! 003 Addressable Relay Module (Fan Shutdown) ABC FIRE SYSTEMS ALL SYSTEMS NORMAL 15-Jan-00 3:10 PM A fire erupts at the Heat sensor (Point 001) while the system is polling the Smoke Detector (Point 002) Digital Loop Response Addressable Heat Sensor Addressable Smoke Sensor 001 002 Addressable Input Module (Waterflow) Addressable Pull Station 004 Addressable Smoke Sensor 006 005 FIRE! 003 Addressable Relay Module (Fan Shutdown) ABC FIRE SYSTEMS ALL SYSTEMS NORMAL 15-Jan-00 3:10 PM The Heat Sensor (Point 001) interrupts the polling process to handle the alarm immediately Digital Loop Response Addressable Heat Sensor Addressable Smoke Sensor 001 002 Addressable Input Module (Waterflow) Addressable Pull Station 004 Addressable Smoke Sensor 006 005 FIRE! 003 Addressable Relay Module (Fan Shutdown) ALARM POINT 001 HEAT SENSOR 15-Jan-00 3:10 PM ALARM! THE END Hochiki America Corporation 7051 Village Drive, Suite 100 Buena Park, California 90621 www.hochiki.com