Division method of dangerous areas of the hottest

Classification method of dust explosion hazardous areas

1 significance of classification of dust explosion hazardous areas combustible dust will explode under the condition of having a certain concentration (exceeding the lower explosion limit) and sufficient ignition energy. The existence of combustible dust forms a potential explosion environment, and the dangers of these areas can be divided into high and low. Therefore, it is necessary to classify these dangerous areas, so as to take corresponding explosion-proof measures according to the type of dangerous areas, so as to minimize the possibility of explosive concentration of combustible dust, the possibility of any ignition source, and the possibility of both at the same time, Minimize the possibility of dust explosion. The State Administration of work safety clearly stipulates in the code for safety acceptance and evaluation that whether there is a scientific and accurate regional division for the hazardous environment of dust explosion is an important part of the acceptance and inspection items. At the same time, scientific division of hazardous areas is also of great significance for saving project investment. The price of dust explosion-proof equipment is 2-3 times that of ordinary products. Only by scientifically dividing dangerous areas can explosion-proof electrical equipment be reasonably selected to avoid waste. 2 principles for the division of dust explosion hazardous areas China has long formulated the principles for the division of dust explosion hazardous areas, such as the code for electrical safety in explosion hazardous areas (gbj58-83) and electrical equipment in explosive dust environment: dust explosion proof electrical equipment (GB12476.1 has achieved the historical breakthrough of the Chinese nation's centenary "big plane dream" - 2000) (code for design of electrical installations in explosive and Fire Hazard Environments) (gb50085-92), (safety code for dust explosion in grain processing, storage and transportation systems) (GB 17440-1998), etc. are described in detail. The International Electrotechnical Commission (IEC), the American electrical code (NEC) and Germany, Japan and other countries have provisions on the principle of regional division. However, with the passage of time and different national conditions, the division principles are not consistent. At present, the popular ones in China are "zone 2" (explosion hazardous area and non explosion hazardous area) and "class 2" (zone 10 and zone 11), which are classified according to gb50085-92 and gb17441) - 1998. This division method is being used by iec1241-3 and gb12476.1-2000 "two areas" (classified areas and non classified areas) "Level 3" (zone 20, zone 21, zone 22) Instead, both are divided according to the frequency and duration of explosive dust mixture, as shown in Table 1. Table 1 several popular explosion area classification standards gb50085-92gb17440-98 define iec1241 define explosion hazard area 10 environmental classification area with continuous or long-term occurrence of explosive dust 20 area during normal operation Combustible dust often or frequently occurs. In zone 11, explosive dust mixture occasionally occurs. In zone 21, a sufficient amount of combustible dust and air mixture may be produced during normal operation. In zone 22, combustible dust may be produced infrequently for a short time, and combustible dust layers or deposits may appear, And mixed with the air to form a dangerous non explosive hazardous area, which cannot produce explosive dust under normal or abnormal conditions. Combustible dust in non classified areas will not appear and reach the formation of a noteworthy explosive dust environment. Gb17440 emphasizes the "closed environment" of zone 10, which is only the relative condition or sufficient and necessary condition of dust explosion. IEC 1241 determines the possibility of explosive dust/air mixture according to the release source (i.e. release source level and dust state), and the principles for determining hazardous areas are shown in Table 2. Table 2 classification of dust explosion hazardous areas by release source level dust state dust cloud dust layer often has disturbance and little disturbance lasts (level 0) 202122 main (Level 1) 21212 aluminum Shanxi new materials company 280000 ton Carbon Project No. 3 baking furnace is put into operation 2 secondary (Level 2) 222122 Table 3 classification level characteristic status of release source example 0 continuous release of dust cloud continuous formation of dust cloud may exist continuously or may exist for a long or short term frequently inside dust removal equipment, bucket elevator and other conveying equipment, silos and other equipment 1 main release occasionally formed or periodically formed during normal operation, occasionally or periodically there are semi open electronic scales The intermittent release of human data on the equipment basically does not form. During normal operation, it generally does not release or is infrequent. There are maintenance doors, holes and other so-called releases that are occasionally opened for a short time. Bayer materials technology, the president of silcotech, has 30 production bases and about 14200 employees around the world. Michael Maloney and Gary Lord, the global strategic marketing director of health care of Dow Corning, said that the release source, It refers to the release or rise of dust from a certain point or location, resulting in the formation of explosive dust/air. The classification principle is determined according to the frequency and time, as shown in Table 3. The determination of the release source is the basis for dividing the dangerous area and the dangerous level, because the division of the area level is determined by the danger of the release source and the released dust state, and the area range is determined by the distance from the position of the relative release source. Therefore, it can be said that the correct determination of the release source is the premise of the area division. The principles for determining the location of the release source are as follows: (1) its location occurs in the processing equipment, processing process or processing operation process. (2) Dust clouds are released/generated at this location or