sprinkler system
Sprinkler systems (from English to sprinkle, “sprinkle” or “wet”) act as automatic fire extinguishing systems to prevent a fire that has broken out from developing into a major fire . They are used in special buildings such as high-rise buildings, commercial buildings, department stores , industrial plants, meeting places and underground garages . They are part of the fire protection equipment that is usually required by authorities or insurance companies. Liability for malfunctions and operating errors is very controversial.
History and functioning
The first attempts to fight fires in the early stages were made in American weaving mills. Water-carrying pipes with openings at intervals were placed above the looms. These openings were closed with lids and these were fixed by means of a weight connected to a cotton thread. When a fire broke out, the cotton thread would burn through, the weight yielded, and the opening was opened for water to escape.
Sprinklers were invented in 1874 by the American Henry S. Parmalee, a manufacturer of pianos . Originally the water outlet nozzles were closed with a metal plate that was held in place by a device connected to a fusible link . When exposed to the appropriate temperature, the solder melted, the holding device released the metal plate, this was pressed out by the water pressure, and the water flowing in was sprayed.
Today's sprinklers are closed with glass ampoules, which are filled with a colored special liquid based on glycerine, which in turn contains an air bubble to compensate for the constantly fluctuating air pressure. Several such sprinklers, which are connected to a water pipe network, are installed on the ceiling or in the upper area of the side walls. There is a constant water pressure within the sprinkler system, which is controlled in the sprinkler control unit.
In the event of a fire , the liquid in the glass ampoules heats up. The expansion of this liquid (and compression of the air bubble) ruptures the ampoules, opening the sprinklers and causing water to leak out of the sprinkler piping. In the event of a fire, only the sprinklers whose ampoules have reached the trigger temperature will open. In contrast to this are the so-called water spray extinguishing systems . With these, the pipe network is empty and the nozzles are not closed. This is why water spray extinguishing systems - as known from films - extinguish when triggered with all nozzles belonging to the fire compartment. In Germany, however, this construction method is only used in special situations due to the expected water damage.
The release temperature depends on the size of the trapped air bubble, i.e. H. as the size of the air bubble increases, the activation temperature increases, which is indicated by the color of the ampoule liquid. On average, the trigger temperature is approx. 30 ° C above the expected room temperature.
The pressure drop in the pipe network is detected and leads to the opening of special valves (alarm valve stations) and the starting of pumps (system-specific). From this point on, water is pumped into the sprinkler system from tanks provided for this purpose or via a water connection dimensioned for this purpose at such a pressure that at least about 0.5 bar is applied to each sprinkler. This escapes from all open sprinklers and extinguishes or minimizes the fire .
The pipe network and water supply are dimensioned so that only water is available for a certain number of sprinklers (so-called "effective area"). If more sprinklers open than are provided for the designed effective area, the amount of water available per sprinkler drops and the effectiveness of the system decreases.
Sprinkler systems are therefore mainly able to fight the initial phase of a fire ( incipient fire ) and not to fight a full fire. A fire-resistant partition must be set up between areas without a sprinkler system and areas with a sprinkler system so that a fire that has developed in an unprotected area cannot spread to the section of the building that is protected by a sprinkler system.
The use of a sprinkler system in museums , libraries and archives is problematic . The extinguishing agent water is fundamentally questionable here, as it could damage irreplaceable objects.
Alarm valve station
An alarm valve station is installed between a group of sprinklers and the water supply and is connected to a so-called sprinkler monitoring center (SUZ). If a sprinkler barrel bursts, this causes a pressure drop in the line, which is registered by the alarm valve station. The valve station releases the water supply for extinguishing, triggers an alarm hydromechanically by means of a bell and reports the alarm to the SUZ via a pressure switch. This forwards the signal either to a higher-level fire alarm center or directly to the responsible fire brigade .
Drying system
So-called drying systems are used particularly in areas where there is a risk of frost and the sprinkler lines could freeze. In these systems, the pipeline network between the sprinkler and alarm valve station (here: dry alarm valve station , TAV for short) is filled with compressed air. The system is only filled with water after a sprinkler has been triggered.
Pilot operated sprinkler system
In particularly sensitive areas known to pre-controlled sprinkler systems ( Preactionanlage ) to be installed. Here, too, the lines behind the sprinklers up to the alarm valve station are filled with compressed air, but in the event of a pressure drop (caused by the bursting of a glass jar) water is only given if an automatic fire detector (usually a smoke detector) simultaneously triggers an alarm in the affected area . If no fire is detected by the detector, the (pre-controlled dry alarm ventilation) VTAV remains locked. However, if a fire alarm is triggered before a glass barrel on the sprinkler bursts, the pipe network is already flooded. However, even now, water can only escape if a glass barrel on the sprinkler bursts. If the fire alarm system fails due to a malfunction (e.g. according to DIN VDE 0833), the pre-control on the VTAV is canceled and the VTAV station works as a normal TA valve, so that the function of the extinguishing system is guaranteed at all times.
interpretation
In Germany, sprinkler systems are designed according to VdS CEA 4001 ( VdS Schadenverhütung , CEA Comité Européen des Assurances ) or DIN EN 12845. In Austria, the design is based on ÖNORM EN 12845 and the supplementary TRVB S 127.
The American standards of the NFPA ( National Fire Protection Association ) - in modified or further developed form of the guidelines, also FM standards - are enjoying increasing popularity with international builders and are now generally accepted by German approval authorities. The design depends on the risk of fire in the area to be protected by specifying the water exposure to the source of the fire between 2.25 mm / min and 30 mm / min (1 mm / min corresponds to 1 l / m² / min), the action time between 30 and 90 min and the distance between the sprinklers.
Web links
Individual evidence
- ^ Derbyshire Fire & Rescue Service website
- ↑ Joachim Herz Foundation: Physics - How Sprinkler Ampoules Work
- Richardson, K., Historical Evolution of Fire Protection Engineering, History of Fire Protection Engineering, National Fire Protection Association, Quincy, MA, 2003
- Wermiel, Sara. Mill Fire Protection Methods Enter the Mainstream, (in) The Fireproof Building: Technology and Public Safety in the Nineteenth-Century American City. Baltimore: Johns Hopkins University Press, 2000.
