Modern addressable fire detectors.
The Russian fire safety market is undergoing changes both in the regulatory framework and in technologies. Addressable fire alarm systems (AFAS) are in increasing demand due to the fact that they most fully comply with new regulatory requirements, and are also more effective in detecting a fire hazard than traditional non-addressable ones.
Such systems, as a rule, are polling and have control over the operability of the connected detectors, which allows installing one addressable fire detector per room (in accordance with SP 5.13130.2009) in contrast to traditional non-addressable detectors, of which at least two are required per room. The cost of addressable system equipment is slightly higher than the traditional one, but significantly lower than the cost of addressable-analog SPS equipment. And if you take into account not only the cost of equipment, but also installation, commissioning, and further maintenance, then the cost of the system for the consumer becomes even more attractive. Detectors in modern addressable SPS have, as a rule, the ability to adjust sensitivity within specified limits, mechanisms for its stabilization during operation, control over the dust level with information on the current value, etc. Interest in this class of SPS is increasing every year, and not only from the consumer. There are already more than a dozen manufacturers of addressable SPS on the Russian market today, and, unfortunately, not all of them produce effective systems. In this article, we will consider addressable fire alarm systems from the point of view of their main component – the fire alarm.
The purpose of a fire alarm is to detect a fire at an early stage of development, when it can be extinguished using primary fire extinguishing means with minimal material losses. Most fires (combustion of solid combustible materials) usually begin with smoldering and are accompanied by a significant release of smoke during thermal decomposition, which is carried into the surrounding space by thermal flows. Only a smoke fire alarm can provide early detection. A smoke optical alarm is the most common type of smoke alarm not only in Russia, but throughout the world. Let's consider it in more detail.
What characteristic is of primary importance for the most effective fire detection at the earliest stage? For smoke detectors, this is the sensitivity measured in dB/m. According to GOST R 53325-2009, the sensitivity of optical-electronic smoke detectors must be specified in the technical documentation for the detector and be in the range of 0.05-0.2 dB/m. Certification tests according to GOST R 53325-2009, during which the sensitivity of the detector must remain in this range, allow changes in this sensitivity over a very wide range. For example:
when changing the orientation to the direction of the air flow — by 1.6 times;
when changing the air flow speed — by 0.625-1.6 times;
from copy to copy — by 1.3 times;
when changing the supply voltage — by 1.6 times;
when the ambient temperature changes to +55 0С – by 1.6 times.
With the simultaneous impact of all the listed factors, which usually happens in practice, the sensitivity of the optical-electronic detector can change more than eight times (1.6 x 1.6 x 1.3 x 1.6 x 1.6 = 8.5)! In addition, during operation, the sensitivity decreases due to dust accumulation, aging of electronic components, etc., which further increases the spread.
Unfortunately, almost all Russian manufacturers of addressable fire alarms do not indicate a specific sensitivity value in their product data sheets, but only provide a range of 0.05-0.2 dB/m. Therefore, for the consumer, all alarms look the same in this parameter.
In an addressable fire alarm system, an addressable alarm, just like a traditional non-addressable one, is a threshold alarm, i.e. the response threshold is “flashed” into the alarm itself during its production at the factory. Many unscrupulous manufacturers take advantage of this: having a non-addressable alarm in their arsenal, they “mechanically” convert it into an addressable one, while, of course, this does not provide any advantages in early detection, except for the address of the alarm that triggered the alarm.
The modern level of addressable fire detectors is polling intelligent fire detectors with analog-to-digital converters, non-volatile memory for storing algorithms for processing information, operating modes, the current level of dust in the smoke chamber, and even the date of manufacture, the date of the last maintenance, etc. The use of special algorithms for compensating for changes in sensitivity when the smoke chamber is dusty allows for a stable level of sensitivity during operation. Some manufacturers implement in their detectors the ability to adjust sensitivity within specified limits, which allows adapting the addressable system to the conditions of the controlled object. In clean rooms, increased sensitivity ensures earlier detection of the source of fire, in rooms where the optical density of the environment may change under normal conditions, sensitivity may be reduced to eliminate false alarms.
The sensitivity adjustment function by 1.5–2 times cannot be implemented in every detector. As we have said earlier, according to GOST R 53325-2009, the sensitivity of a smoke detector can be changed by 1.6 times when changing the orientation to the air flow direction, and by 0.625–1.6 times when changing the flow speed from 0.2 to 1 m/s. The dependence of the detector sensitivity on the direction and speed of the air flow is determined only by the shape of the smoke inlet, the design of the smoke chamber, the location of the optocoupler and cannot be compensated for by electronics. With a significant dependence of sensitivity on changes in environmental conditions, sensitivity adjustment loses its meaning and is even unacceptable, since it will lead to going beyond the range of 0.05–0.2 dB/m. Naturally, the requirements of GOST R 53325-2009 for a detector with sensitivity adjustment must be met in the entire range of sensitivity changes, including when setting the extreme values of the range. A careful study of the detector design is required to reduce the dependence of its sensitivity on various factors. For example, consider a non-addressable and addressable detectors from a world-famous manufacturer of fire-fighting equipment, which have the same smoke chamber. If in a traditional detector it was permissible to use a smoke chamber with a flat cover (Fig. 1), then in modern addressable detectors with a sensitivity adjustment function it was necessary to place additional elements on the smoke chamber cover to eliminate the influence of the asymmetrical location of the optocoupler (Fig. 1).
Fig. 1. Smoke chamber and cover of a traditional detector
Is it really necessary to significantly complicate the circuitry and design of the detector to stabilize and adjust the sensitivity? Many believe that it does not matter what the sensitivity of the smoke detector is, it will work anyway someday. However, the simplest experiment clearly shows the dependence of the detection time of a smoldering fire on the set sensitivity of the smoke fire detector.
In the upper part of a small enclosed space (0.1–0.15 m3 is sufficient), addressable smoke fire alarms with varying sensitivity are installed, in the lower part – a smoldering cotton wick on a miniature stand and one or two fans for uniform distribution of smoke throughout the entire volume (Fig. 2).
According to Western experimental estimates, with a specific optical density of smoke of 0.1 dB/m, visibility is approximately 100 m. Considering that at the first stage of the development of a fire, smoke is present only in the upper part of the room, a signal from a smoke detector with a standard sensitivity of about 0.1–0.12 dB/m should provide greater opportunities to stop the development of a fire, protect people and property.
The complexity of measuring the sensitivity of smoke detectors at a facility leads to the fact that detectors are recognized as inoperative only in case of complete failure of the electronics. At one important facility, smoke detectors were tested using smoke from smoldering textile materials. Some detectors did not trigger even when the test source was close, which was explained by their low sensitivity. However, instead of rejecting these detectors, the service personnel «achieved» their triggering by isolating the detector and the source from the external environment using a polyethylene sleeve and thereby increasing the smoke concentration to unrealistic values. But even such a simple test of the threshold system requires a significant investment of time and is carried out only at some facilities. Modern intelligent addressable SPS provide the ability to read the set sensitivity level and even the level of dust and smoke in the smoke chamber from the non-volatile memory of the detector. As a rule, this is possible with the help of additional accessories, which may be called differently by different manufacturers. Ease of use of accessories is not the last factor when choosing a system. There is a difference in testing the detector with a button, a sharp object, a magnet, or using a universal remote control with an LCD screen, where all current information about the detector is displayed (Fig. 3).
Fig. 2 Multifunctional remote control
Ease of setting and reading the address plays an important role. Different manufacturers use different methods of recording detector addresses. One such example of a method of setting addresses is rotary address switches, which are located on the back of the detector (Fig. 4), which makes it possible to determine or change the current number of the detector without connecting it to the control panel.
Fig. 3. Rotary switches for setting addresses
Another example is a method of recording an address in the non-volatile memory of the detector using additional devices such as an address programmer (Fig. 5). This method of setting the address is the most common in addressable fire alarm systems.
Fig. 4 Address programmer
And in conclusion, I would like to consider another type of fire alarm — aspiration. No other alarm provides such a level of fire detection efficiency. Today, many Western companies, manufacturers of addressable fire alarm systems, consider this technology to be one of the most promising and provide the ability to connect an aspiration alarm to their addressable control and monitoring devices (CMD).
The simplest addressable aspiration smoke fire alarm consists of a pipe with holes for taking air samples, which enter a block with a highly stable turbine and with optical density meters of the environment, as a rule, these are point intelligent addressable smoke alarms with sensitivity stabilization, which are connected to the addressable loop of a compatible control panel directly. And information from the aspiration block (power supply failure, pipe system break, clogged holes, etc.) is transmitted to the addressable control panel via the «Fault» relay. The pipe is located in the controlled area, and the aspiration device — the central block, can be installed in a place convenient for control and maintenance in the same or another room.
Fig. 5 Aspiration system
Aspiration control method – constant forced air extraction through a system of pipes from the controlled volume provides significant advantages over traditional point detectors, which under certain conditions are simply not reached by smoke. The aspirator ensures the flow of air from a sufficiently large volume of the room through each hole, which compensates for the influence of air flows from supply and exhaust ventilation, air conditioning systems, etc., which distort the “standard” distribution of smoke in the room. Aspiration also reduces the effect of air stratification (layering) in a high room, when a layer of warm air under the ceiling prevents smoke from entering the upper part of the room. In addition, the simultaneous flow of smoke through several holes in the pipe compensates for the decrease in smoke concentration under the ceiling in a high room.In this article, we tried to look at addressable fire alarm systems from the point of view of a fire detector. Since this class of systems represents the next stage in the development of fire alarm systems, upgrading the detector class — traditional threshold, intelligent addressable with sensitivity adjustment — requires not only more complex circuitry, but also a higher level of design development of the detector, smoke chamber and optocoupler. Otherwise, the stability of sensitivity and efficiency of the detector will be practically no different from simpler models. Only modern addressable systems that use advanced fire detection solutions, such as aspiration systems, and intelligent addressable detectors with sensitivity adjustment and its stabilization during operation, can provide the required level of fire protection for an object.
ASD (System Sensor) series aspiration detectors
Maximum rapid detection of a fire hazard. Reduction of the influence of air flows. Embedding in decorative elements and building structures. No loops and electronic devices in the protected premises. Convenient design program. Easy installation, programming and maintenance. Minimum costs when upgrading a fire alarm system.
Application area – ultra-clean rooms, containment areas (microelectronics production), processing shops (woodworking, paper, tobacco factories), buildings with non-standard architecture, glass atriums, historical architecture, museums, libraries, archives. Ideal solution for long and high rooms (up to 15 m), warehouses. Areas with electronic equipment (server rooms, data centers, telecommunication systems). Spaces behind suspended (stretch) ceilings under double floors, hard-to-reach and dusty areas. Elevator shafts, escalators, tunnels.
«Invisible» automatic smoke detector Bosch series 520 (Bosch Security Systems)
The ultra-thin FAP-0-520 smoke detectors not only reliably detect fire symptoms, but also fit well into the interior of the premises, as they are mounted flush to the ceiling and allow the use of color inserts to match the overall interior color scheme. They are designed specifically for connection to the LSN improved local security network, and two built-in isolators allow you to maintain the functions of the ring loop in the event of a wire break or short circuit. Bosch FAP-520 are equipped with two optical sensors and a pollution sensor, while the sensor does not have an optical chamber in its usual sense. The sensor has 2 built-in LEDs that emit a light flux at a certain angle into the working area under the detector, and when smoke particles get there, photodiodes measure the amount of reflected light in a virtual optical chamber and convert it into a proportional electrical signal. To eliminate false alarms, the detector uses 2 virtual optical chambers operating on the «I» logic, and the photodiode is sensitive only to IR radiation coming from the LED. In addition, the FAP-0-520 has a pollution compensation mechanism, and the corresponding sensor issues a signal when the detector needs cleaning.
Addressable analog linear smoke detectors 6500 and 6500S (ESMI)
Single-position addressable analog linear optical-electronic smoke detectors 6500 and 6500S are designed to operate in the ESMI FX NET fire alarm system. The detectors are fully compatible with the 200+ protocol and are used to protect rooms with high ceilings and ceilings of complex shapes (atriums), as well as extended rooms (warehouses, hangars, etc.).
The 6500S and 6500 detectors have a transmitter and receiver in one housing. The transmitter generates an infrared beam in the direction of the reflector. The beam reflected by the reflector hits the receiver, and the received signal level is analyzed. The alarm condition is determined by the change in the intensity of the received signal. The 6500S detector has a unique remote testing capability. «Fine tuning» of the detector together with the reflector can be achieved thanks to the digital signal intensity indicator.
The sensitivity of the detector can be set between 25% and 50% attenuation, which provides flexibility in adapting to environmental conditions. The detector also implements automatic sensitivity compensation technology.
Addressable smoke detector IQ8Quad-802371 (Esser by Honeywell)
The IQ8Quad-802371 optical smoke detector provides reliable early fire detection. It is capable of detecting smoke emitted by various combustion products and complies with the design standards for fire alarm systems in the Russian Federation. Like all models in the IQ8Quad series, this detector is equipped with a short-circuit isolator and has an extremely low quiescent current consumption. It has a flat housing, but at the same time a capacious mounting base, standard for all detectors in this series. The presence of such a base allows you to replace the camera without opening the fire loop and with an active alarm. In addition, the manufacturer produces a modification of the smoke detector with a built-in siren, the volume of which reaches 92 dB, which eliminates the need to install additional acoustic warning devices.
Leonardo Addressable Fire Detector Series (System Sensor)
Possibility of installing 1 addressable detector with automatic performance monitoring in the room instead of 2 non-addressable ones (clause 13.3.3 SP 5.13130.2009). Minimum cable consumption: two-wire addressable bus for 99 detectors of any topology. Elimination of an additional loop for protecting the ceiling space. All this ensures total cost savings at the stage of delivery of the Leonardo addressable system compared to the non-addressable one, especially at small and medium-sized facilities. Early and reliable detection of a fire hazard situation with indication of the address of the activated detector.
Compatible with addressable fire alarm and security devices PPKOPA «Signal-99», «Kvazar-A», S632-2GSM (Proxyma), as well as with any non-addressable threshold PPKP and PPKOP — through the addressable module AM-99 with the relay «FIRE1», «FIRE2» and «MALFUNCTION». The warranty for addressable detectors of the Leonardo series is 5 years.
Addressable aspiration smoke detector VESDA VFT-15 (Xtralis Ltd)
A distinctive feature of this detector is its addressability. Using the VFT-15, it is now possible to determine not only in which air intake pipe, but also through which opening the smoke entered the VESDA system. Addressable smoke detection is performed within a radius of up to 50 m from the detector. At the same time, the minimum smoke concentration that the VFT-15 recognizes is only 0.001% obscuration/m.
Innovative solution from Xtralis allows to significantly increase fire safety of such objects as server rooms, data processing centers, archives, telephone exchanges, hotels, correctional technical institutions, etc., where it is necessary to accurately (for example, with an accuracy of the server rack) determine the location of the fire hazard source.
Addressable fire smoke detectors «AVRORA-DA» (IP 212-79) (Argus Spectr)
Work together with addressable fire control panels «RADUGA-2A» and «RADUGA-4A».
Automatic continuous analysis of the detector's performance. The patented smoke chamber has 2 dust collectors. Power supply via a two-wire line from the fire control panel. The reflector system provides protection from external illumination, and the symmetrical smoke chamber is sensitive to smoke in all directions. The built-in protective mesh is a reliable barrier for insects. The reed switch allows testing the detector using a magnet. Setting the address and operating mode of the detector with the Aurora-2P programmer. Mounting bases (main, reinforced, high) with a central location of contacts ensure ease of installation and easy replacement of detectors.
The detector operates stably in the temperature range from -30 ° C to + 55 ° C.