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Interrelated water mist fire extinguishing system to understand the mechanism of

    A brief introduction of water mist: "mist" (watermist) is relative to the "Water Spray" (waterspray) concept, the so-called water mist, is the use of a special nozzle, the water produced by high pressure water jet particles.

    In NFPA750, the fine mist is defined as: the minimum design working pressure, 1 m away from the nozzle plane, measured the thickest portion of the water mist particle diameter of not more than Dv0.99 1000μ.

    The origin and development of water mist.

    Water mist in the application of fire began in the forties, which was mainly used in special places, such as transport and so on. Now because of environmental issues, fire extinguishing agents to be phased out,ratchet tie dowm and water mist fire extinguishing agent as a potential advantage for the environment so that it continues to expand the scope of application, water mist fire extinguishing systems for residential buildings, flammable liquid storage facilities and electrical equipment, research, encouraging results have been achieved.

    1993, from engineering and scientific research departments, water mist system manufacturers, insurance companies, administrative authorities and representatives of industrial users to form the American Federation of water mist fire extinguishing systems technology committee, which began with the preparation of Specifications of water mist technology in NFPA standards as the basis for the design and installation.

    In 1996, Boston, Massachusetts, United States, May 20-23, every year the annual meeting of the Technical Committee of water mist system mist specifications submitted and received approval from the National Fire Protection Association. The specification by the National Standards Institute on July 18 the same year issued with effect from August 9, the same year on July 26, 96, was approved for the U.S. version of NFPA750 national norms.

    Water mist fire extinguishing mechanism and application.

    Water mist fire extinguishing system the key to success is to increase the surface area per unit volume of water particles. After the particles of water, even if the same volume of water, but also can increase the total surface area. The surface area increases, the more easily absorb heat, cooling the combustion reaction. Easily absorb the heat of vaporization of water particles, volume increased about 1,700 times. As the generation of steam, both dilute the concentration of oxygen near the flame, choking the combustion reaction, and effective control of the thermal radiation. That the water mist fire suppression mainly through high-efficiency cooling and the dual role of hypoxia asphyxia.

    Water mist particle diameter size distribution of water and fire-fighting capacity is a complex relationship issues. In general, Level 1 and Level 2 water mist for fire fighting liquid fuel tanks better, and will not stir the pool surface. Typically, a water mist with the first Class A combustibles fight is difficult, which may be can not penetrate the carbon layer of water mist and wet combustion. However, because of the high speed jet of water mist, burning at the surface or in the closed space, is conducive to the case of oxygen reduction, or to fight Class A combustibles. This shows that, for certain combustion, the particle diameter of water mist fire-fighting capacity is not the only factor in the decision. System, water mist fire suppression results were compared with the flame jet direction, speed and water density, which are closely related.

    Tests showed that a single low-pressure system to produce a larger flow of water particles in the fight against Class A fire deep, showing good results. This is due to its relatively large flow (single-flow high-pressure system, 3 to 4 times), resulting in a surface wetting effect, but weakens the system by blocking the fire fighting capabilities. The single-flow high-pressure fire fighting system is exactly the opposite effect, due to the smaller diameter of the water particles to improve the ability to fight fires by blocking, and weakened the fight against deep-seated Class A fire effects. Test showed that the large space by blocking the fire, when the fire at the oxygen concentration to 18% or less, the flame can be extinguished.

    Water mist fire extinguishing systems and Halon gas fire suppression system or other than fire-fighting for much longer, the former is about 100-200 seconds, which is about 10-20 seconds.

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