Classification of explosion-proof electrical equipment
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Electrical equipment for explosive environments is divided into classes I, II and III.
Type I
Class I electrical equipment is used in coal mine gas environment.
Note: Class I explosion-proof type takes into account the ignition of methane and pulverized coal and the increased physical protection measures of underground equipment.
Electrical equipment used in coal mines, where the environment may contain other explosive gases in addition to methane, shall be manufactured and tested in accordance with the requirements of class ⅰ and ⅱ corresponding combustible gases. Such electrical equipment should be marked (for example, "Ex D I/IIB T3" or "ExdI/II(NH3)".
Class II
Class II electrical equipment is used in explosive gas environments except coal mine methane gas.
Class II electrical equipment may be further subclassified by the type of explosive environment in which it is intended to be used.
Reclassification of Class II electrical equipment:
Class IIA: representative gas is propane;
Class IIB: representative gas is ethylene;
IIC: The representative gas is hydrogen.
Note 1 The above classification is based on the maximum test safety gap (MESG) for flameproof enclosure electrical equipment and the minimum ignition current ratio (MICR) for intrinsically safe electrical equipment (see GB3836.11-2010 and GB3836.12-2010).
Note 2: Mark IIB equipment can be applied to IIA equipment conditions, mark IIC class equipment can be applied to IIA and IIB class equipment conditions.
Class III
Class III electrical equipment for use in explosive dust environments other than coal mines.
Class III electrical equipment may be further subclassified according to the characteristics of the explosive dust environment in which it is intended to be used.
Reclassification of Class III electrical equipment:
Class IIIA: inflammable catkin;
Class IIIB: non-conductive dust;
Class IIIC: conductive dust.
Note: Mark IIIB equipment can be applied to IIIA equipment conditions, mark IIIC class equipment can be applied to IIIA or IIIB class equipment conditions.
Equipment for specific explosive environments
Electrical equipment may be tested for a particular explosive environment, in which case the relevant information shall be recorded in the explosion-proof certificate and marked on the electrical equipment accordingly.
