Detailed explanation on the classification of explosion-proof grade of explosion-proof electrical equipment

The definition of explosion-proof grade the classification of explosion-proof grade of explosion-proof electrical equipment is based on the type of equipment used, the temperature group of explosive gas mixture and the explosion-proof type of explosion-proof electrical equipment The explosion-proof electrical equipment is divided into two categories: Category I refers to the electrical equipment used in the coal mine; category II refers to the electrical equipment used in places other than the coal mine According to the Zui large test safety gap (MESG) or Zui small ignition current (MICR), category II electrical equipment is divided into three categories: IIA, IIb and IIC The above four categories are mainly based on the Zui small spark energy that may detonate under different working conditions China, Europe and most countries and regions in the world divide the explosive gas into these four risk levels The specific differences are as follows: group comparison: Secondly, according to the difference of ignition temperature, the explosive gas mixture is divided into six groups: T1, T2, T3, T4, T5 and T6 The ignition temperature is expressed in t (℃) The ignition temperature of each group is: T1: 450 ℃ T2: 300 ℃ T3: 200 ℃ T4: 135 ℃ T5: 100 ℃ T6: 85 ℃ Thirdly, for different purposes, the explosion-proof types of explosion-proof electrical are different, mainly including: 1 Explosion-proof type, marked D; 2 Increased safety type, marked E; 3 Positive pressure type, marked p; 4 Intrinsic safety type, marked I, 5 Oil filled type, marked o; 6 Sand filled type, marked Q; 7 Spark free type, marked n; 8 Cast in type, mark m; 9 Air tight type, mark H [edit this paragraph] example: the explosion-proof mark is dIIBT4, which represents: the explosion-proof electrical products are of explosion-proof type, which are of class IIB (class) used in class II places, and the ignition temperature of explosive gas is of class T4 The basic principle of explosion-proof the concept of explosion is that a substance changes from one state to another after physical or chemical changes, and emits huge energy The energy released at a rapid speed will make the surrounding objects suffer violent impact and damage Explosion must have three conditions: 1) explosive substances: substances that can react with oxygen (air), including gas, liquid and solid (gas: hydrogen, acetylene, methane, etc.; liquid: alcohol, gasoline; solid: dust, fiber dust, etc ）2) oxygen: air 3) ignition source: including open fire, electrical spark, mechanical spark, electrostatic spark, high temperature, chemical reaction, light energy, etc Why explosion-proof and explosive substances: many production places will produce some combustible substances About two-thirds of the underground places in coal mines have explosive substances; in the chemical industry, about 80% of the production workshop areas have explosive substances Oxygen: oxygen is everywhere in the air Ignition source: a large number of electrical instruments are used in the production process Various kinds of friction electric sparks, mechanical wear sparks, electrostatic sparks, high temperature, etc are inevitable, especially when the instruments and electrical faults occur Objectively, many industrial sites meet the explosion conditions When the mixture concentration of explosive substance and oxygen is within the explosion limit, if there is an explosion source, explosion will occur Therefore, it is necessary to take explosion-proof measures Principle of instrument explosion-proof hazardous area division: definition of explosive substance area China standard North American Standard area 0: Div.1 gas (class I) under normal conditions, explosive gas mixture continuously or for a long time area 1: under normal conditions, explosive gas mixture is likely to occur area 1: div.2 Under normal conditions, explosive gas mixture is unlikely to occur, only under abnormal conditions, occasionally or for a short period of time, area 10 Div.1: dust or fiber (class II / III) under normal conditions, the mixture of explosive dust or combustible fiber and air may be continuous, Div.2, zone 11, short-term frequent or long-term presence: under normal conditions, explosive dust or mixture of combustible fiber and air cannot appear, only under abnormal conditions, The applicability of occasionally or short-term explosion-proof methods to hazardous areas: No explosion-proof type code national standard explosion-proof measures applicable area 1 explosion-proof type D gb3836.2 isolated ignition source Zone1, zone2 increased safety type E gb3836.3 try to prevent the generation of ignition source Zone1, Zone2 3 intrinsically safe type Ia gb3836.4 energy of restricted ignition source zone0-2 intrinsically safe type Ib gb3836.4 energy of restricted ignition source Zone1, zone2 4 positive pressure type P gb3836.5 hazardous substance and ignition source Zone1, zone2 5 oil filled type O gb3836.6 hazardous substance and ignition source Zone1, zone2 6 sand filled type Q gb3836.7 hazardous substance and ignition source Zone1, zone2 7 non sparking type n gb3836.8 try to prevent the generation of ignition source zone2 8 pouring type m gb3836.9 try to prevent the generation of ignition source Zone1, zone2 9 airtight type H gb3836.10 try to prevent the generation of ignition source Zone1, The applicability of zone2 explosion-proof to dangerous places: according to the classification of explosive dangerous gases, according to the small spark energy of Zui that may detonate, explosive gases are divided into four risk levels in China, Europe and most countries and regions in the world, as shown in the following table: working condition category gas classification substitute for surface gas Zui small spark energy mine I methane 0.280mj The plants outside the mine Ⅱ a propane 0.180mj Ⅱ B ethylene 0.060mj Ⅱ C hydrogen 0.019mj in the United States and Canada first divided the explosive objects scattered in the air into three classes: class I gas and vapor; class II dust; class III fiber Then the gas and dust were divided into group (Group): Representative gas or dust A acetylene B hydrogen C ethylene D propane e metal dust f coal dust g grain dust gas temperature group division: temperature group safe object surface temperature common explosive gas T1 ≤ 450 ℃ hydrogen, acrylonitrile, etc 46 T2 ≤ 300 ℃ acetylene, ethylene, etc 47 T3 ≤ 200 ℃ The meaning of explosion-proof mark ex (IA) Ⅱ C T6 for 36 kinds of T4 ≤ 135 ℃ acetaldehyde, tetrafluoroethylene, etc and 6 kinds of T5 ≤ 100 ℃ carbon disulfide instruments: the meaning of mark content symbol explosion-proof declaration ex meets some explosion-proof standards, for example, IA is adopted as the national standard explosion-proof mode IA in China Class II intrinsically safe explosion-proof method, which can be installed in Zone 0, gas class II C, which is allowed to involve class II C explosive gas temperature group T6, the surface temperature of the instrument does not exceed 85 ℃, ex (IA) II C, the meaning of the sign content, the meaning of the explosion-proof declaration, ex complies with the European explosion-proof standard, explosion-proof mode IA, which adopts class IA intrinsically safe explosion-proof method, and can be installed in Zone 0 gas category Ⅱ C is allowed to involve explosive gas category Ⅱ C: Note: there is no temperature group item in the sign, indicating that the instrument is not in direct contact with explosive gas Explosion proof terminology: relevant explosion-proof terminology and standard safety barrier safety parameter definition: * 8226; Safety barrier Zui high allowable voltage: Um ensures the intrinsic safety performance of safety barrier intrinsic safety end, and allows the Zui high voltage * 8226 that may be input by non-native safety end; safety barrier Zui high open circuit voltage: when UOC is in the range of Zui high allowable voltage, the voltage Zui high value * 8226 when the intrinsic safety end is open circuit; Safety barrier Zui large short-circuit current: the current Zui large value * 8226 when ISC is short circuited at intrinsically safe terminal within the range of Zui high allowable voltage; safety barrier allowable distributed capacitance: CA under the condition of ensuring intrinsic safety performance, the allowable external capacitance at intrinsically safe terminal * 8226; safety barrier allowable distributed inductance: La under the condition of guaranteeing intrinsic safety performance, the allowable external inductance at intrinsically safe terminal Zui Explosion proof sign format description: the explosion-proof sign and explosion-proof form of explosion-proof equipment on site shall be determined by scientifically classifying and classifying the explosion-proof dangerous medium in the factory or mining area according to its ignition energy, Zui small ignition temperature and the time period of the existence of explosive dangerous gas on site Format of explosion-proof sign: ex (IA) Ⅱ C T4 explosion-proof sign explosion-proof grade gas group temperature group explosion-proof grade Description: ia grade: electrical equipment that cannot ignite explosive gas mixture in normal operation, one fault and two faults In normal operation, the safety factor is 2.0; in one failure, the safety factor is 1.5; in two failures, the safety factor is 1.0 Note: the contact with spark must be equipped with flameproof shell, airtight shell or double to improve the safety factor Class Ib: electrical equipment which cannot ignite explosive gas mixture in normal operation and a fault In normal operation, the safety factor is 2.0; in case of a fault, the safety factor is 1.5 In normal operation, the contact with spark must be timed with a safety factor of 1.0 Shi, a fault