The present situation and application of the fire

2022-08-07
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The present situation and application of water mist fire extinguishing system Abstract: the development situation, fire extinguishing mechanism, performance characteristics and application scope of water mist fire extinguishing system are briefly described. Based on some fire extinguishing test parameters at home and abroad, the fire extinguishing efficiency, application site, project cost and problems to be solved of water mist fire extinguishing system are explained, and the good engineering application prospect of water mist fire extinguishing system is prospected

key words: water mist; DV0.99; Typical test; Fire fighting efficiency

1 preface

fire will cause huge losses to people's lives and property, and the fire fighting work is "more important than Mount Tai". All countries in the world are committed to the research of new fire protection technology. It is the direction of people's efforts to develop fire-fighting technology that not only has high fire-fighting efficiency, but also has no pollution to the environment. In particular, it is found that halon fire extinguishing agent used has a destructive effect on the atmospheric ozone layer. After the signing of the Montreal Protocol, this work is particularly urgent. Water mist fire extinguishing technology is the representative of this direction. Therefore, it has attracted more and more attention

2 overview of the development of water mist fire extinguishing system

since ancient times, people have known how to use water to extinguish fires. "Water and fire are incompatible, and water and fire are mutually exclusive" has been well known in ancient times. Therefore, water is the earliest fire extinguishing agent used by human beings. With the development of human society and the progress of science and technology, great changes have taken place in the types and forms of fires, and the methods of human using water to extinguish fires have also developed accordingly. See Table 1 for the development of water fire extinguishing utilization mode

the application of water mist fire extinguishing technology in fire fighting began in the 1940s, when it was mainly used in special places, such as transportation vehicles. As the water spray fire extinguishing technology was the main development and research direction at that time, the water mist fire extinguishing technology had not been deeply studied, so it had been developing slowly. With the progress of science and technology, the change of people's concept of fire prevention and extinguishing, especially the discovery that halogenated alkyl fire extinguishing agents have a destructive effect on the atmospheric ozone layer and the signing of the Montreal Protocol on substances that Deplete the ozone layer in 1987, water mist fire extinguishing technology, as one of the main alternative technologies of Halon, has attracted the attention and favor of all walks of life. Water mist fire extinguishing technology developed rapidly in the 1990s

1996, at the annual meeting of the American Fire Protection Association in Boston, Massachusetts, the water mist fire extinguishing system Technical Committee submitted the water mist fire extinguishing system standard and obtained the approval of the American Fire Protection Association. It was promulgated on July 18 of the same year and implemented on August 9. On July 26, the 96 edition n FPA 750 was approved as a US national specification. This is the first specification for design and installation of water mist fire extinguishing system in the world, and it is a performance-based specification. Its appearance further promotes the in-depth study of water mist fire extinguishing technology, and also indicates that the application of water mist will enter a new stage

many developed countries (mainly European and American countries) have successively developed various types of water mist fire extinguishing systems after years of theoretical test exploration and applied research. And began to be widely used in relevant fields and places. At present, some products have entered the domestic market, and some have been put into use

in the late 1990s, China began the research, development and test of water mist fire extinguishing system, which was listed as the national "Ninth Five Year" scientific and technological research project. It mainly refers to the NFPA 750 standard of the United States and carries out various research and development work in combination with the actual application in China. So far, two corresponding water mist fire extinguishing systems, which can be divided into inert materials and degradable materials, have been successively developed. At present, the existing products can also adopt a single sample processing system and its application

at present, the competent authorities in Beijing, Zhejiang and Hubei have formulated corresponding specifications for design, construction and acceptance of water mist fire extinguishing system, and the competent authorities in Jiangsu and Hunan are also formulating corresponding specifications for design, construction and acceptance. It is believed that with the extensive application of water mist products, national water mist fire extinguishing system design, construction and acceptance standards and specifications will be issued soon

3 definition and classification of water mist

3.1 definition of water mist

water mist: under the minimum design pressure of the nozzle and on the plane 1 m away from the nozzle, the measured droplet diameter D at the coarsest part of the water mist is smaller than V 0199 and does not exceed 1000lm. This is a method to express the droplet diameter by volume method. DV 0.99 means less than 1000 μ The diameter volume content of M is 99%. Generally, water mist refers to droplet diameter DV 0199 ≤ 400 μ M

volume 99% diameter DV 0.99: a method to express the droplet size in terms of the volume of spray droplets. When measured by volume, it means that 1% of the total volume of spray droplets is composed of droplets with a diameter greater than this value, and the other 99% is composed of droplets with a diameter less than this value

3.2 classification of water mist

according to the size distribution of water particles in spray water mist, water mist can be divided into three categories, as shown in Figure 1

class I water mist: the cumulative percentage volume distribution curve is all located at the connection DV 0.1= 100 μ M and DV 0.9= 200 μ On the left of the M line, this represents the finest water mist. At present, most manufacturers produce class 1 water mist nozzles

class II water mist: it is part of the cumulative percentage volume distribution curve, which is outside the limit of class I spray, but it is all connected with DV 0.1= 200 μ M and DV 0.9= 400 μ The left side of the M line. This kind of water mist can be produced by pressure jet nozzle, two-phase flow nozzle and many impact nozzles. Due to the appearance of large water droplets, class II water mist is easier to produce large flow than class I water mist

class III water mist: DV 0.9> 400 μ m. Or there are many companies committed to graphene production and utilization in the UK. Any part of the curve exceeds the right side of the class II boundary (but DV 0.9

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