Explosion-proof electrical equipment: electrical equipment designed and manufactured according to the specified conditions (explosion-proof type) without causing the explosion of explosive mixtures (explosive hazardous places), that is, an electrical equipment applied to explosive environments. Equipment for use in explosive environments: refers to electrical explosion-proof equipment used alone or in combination in explosive environments to prevent explosions caused by their own potential ignition sources.

1. Classification of electrical equipment for explosive environments

1.1 Electrical equipment for explosive environments is divided into Class I, Class II and Class III.

Class I: For coal mine gas environment.

The explosion-proof type of Class I equipment takes into account the ignition of gas and coal dust and the increased physical protection measures of underground equipment. Equipment used in coal mines, when the environment may contain other explosive gases in addition to gas, shall be manufactured and tested in accordance with the requirements of the corresponding combustible gases of Class I and Class II.

Class II: For explosive gas environments other than coal mine gas environments.

They can be further reclassified according to the characteristics of the explosive gas environment in which they are intended to be used.

Reclassification of Class II equipment:

Class A: The representative gas is propane;

Class II B: The representative gas is ethylene;

ⅡC class: The representative gases are hydrogen and acetylene.

Note: Class ⅡB equipment is applicable to the conditions of use of class ⅡA equipment, class ⅡC equipment is applicable to the conditions of use of class ⅡA and class ⅡB equipment. ⅡC class equipment indicates that the explosion-proof level is high, but it does not mean that this type of equipment has the best performance.

Class III: For explosive dust environments other than coal mines.

Class III equipment can be further classified according to the characteristics of the explosive dust environment in which it is intended to be used.

Reclassification of Class III equipment:

-- Ⅲ Class A: Combustible floc;

Class III B: non-conductive dust;

Class III C: conductive dust.

Note: Class ⅢB equipment is suitable for the use conditions of class ⅢA equipment, class ⅢC equipment is suitable for the use conditions of class ⅡA or class ⅢB equipment.

1.2 Equipment for a specific explosive gas environment shall be tested according to a specific explosive gas environment, in which case the relevant information shall be recorded in the explosion-proof certificate and marked accordingly on the equipment.

2. Device protection level EPL

2.1 Definition:

EPL (equipment protection level) : Equipment used in explosive environments, according to the possibility of the equipment to become the ignition source and the explosive gas environment, explosive dust environment and coal mine methane explosive environment has different characteristics of the protection level of the equipment.

2.2 Classification

Coal mine gas: Ma, Mb;

Explosive gas environmental equipment: Ga, Gb, Gc;

Environmental equipment for explosive dust: Da, Db, Dc.

Iii. Regional classification

3.1 Explosive gas environment according to the frequency and duration of occurrence is divided into:

Zone 0: Explosive gas is always present or for a long time; Continuously present an area with a risk greater than 1000 hours/year;

Zone 1: Flammable gases may occur or be present during the normal operation of the instrument; Intermittently present danger areas of 10 to 1000 hours/year;

Zone 2 (Zone 2) : In general, there is no flammable gas and even if it occurs occasionally, its existence is short; The danger exists in the accident state 0.1~10 hours/year area;

3.2 Combustible dust environment is divided into: according to the frequency, duration and dust layer thickness:

Zone 20: During normal operation, combustible dust occurs continuously or frequently in quantities sufficient to form mixtures of combustible dust with air or in the interior of containers where uncontrollable and extremely thick dust layers may form.

Zone 21: During normal operation, the amount of dust that may occur is sufficient to form a mixture of combustible dust and air, but is not classified as Zone 20. This area includes places directly adjacent to the point of charging or discharging dust, places where dust layers occur, and places where mixtures of combustible dust and air may produce combustible concentrations under normal operation.

Zone 22: Under abnormal conditions, flammable dust is occasionally present and only for a short time, or flammable dust is occasionally accumulated or there may be dust layers and an air mixture of flammable dust is produced. If it is not possible to guarantee the exclusion of combustible dust accumulation or dust layer, it should be divided into 21 zones.