1. Explosion-proof electrical equipment knowledge

(1) Hazardous Locations: According to the provisions of GB3836.14-2000 "Electrical Equipment for Explosive Gas Environments Part 14: Classification of Hazardous Locations", hazardous locations can be divided into Zone 0, Zone 1, Zone 2.

(a) Zone 0: Sites where explosive gas atmospheres occur continuously or for a long period of time.

(b) Zone 1: Locations where explosive gas atmospheres may occur during normal operation.

(c) Zone 2: In normal operation, it is not possible to have an explosive atmosphere, and if it does occur, it occurs occasionally and only for a short period of time.

(2) Category: The type of electrical equipment is related to the use environment. There are mainly two categories:

Category I: Coal mining electrical equipment.

Category II: Other explosive gas atmospheres other than coal mines.

Type II flameproof type "d" electrical equipment according to the maximum experimental safety gap, intrinsically safe "i" electrical equipment according to the minimum ignition current is divided into IIA, IIB, IIC category (IIB category the most widely used, only hydrogen Sites such as acetylene are required to use Class IIC, see Table 3).

(3) Maximum surface temperature: The highest temperature of any part or surface that can cause ignition of the surrounding explosive atmosphere when the electrical equipment is operated under the most unfavorable conditions within the permissible range.

(4) Ignition temperature: The minimum temperature at which a combustible gas or mixture of steam and air is ignited by a hot surface under specified conditions (see Table 1).

(5) Temperature group: The group of electrical equipment divided by its maximum surface temperature (see Table 1).

Table 1 Relationship between temperature group, surface temperature and ignition temperature

Electrical equipment temperature group	The maximum surface temperature of electrical equipment	Gas or vapor ignition temperature
T1	450℃	＞450℃
T2	300℃	＞300℃
T3	200℃	＞200℃
T4	135℃	＞135℃
T5	100℃	＞100℃
T6	85℃	＞85℃

(6) Dust explosion hazardous locations: According to the frequency and duration of the explosive or flammable dust environment, dust explosion hazardous locations are divided into:

Zone 10: Zones in which explosion or explosion of dust clouds or dust layers that may occur or may occur during normal processing, treatment or cleaning.

Zone 11: Sites not designated as Zone 10, but under unusual conditions, areas where dust clouds or dust layers mixed with air can reach explosive concentrations can occur.

(7) The relationship among dust temperature group, ignition temperature, and maximum surface temperature (Table 2).

Table 2

Temperature group	Lighting temperature T	Highest surface temperature
Temperature group	Lighting temperature T	No overload	With approved overload
T11	T＞270℃	215℃	190℃
T12	＜200℃T≤270℃	160℃	145℃
T13	＜150℃T≤200℃	120℃	110℃

(8) Examples of flammable gases that are allowed in the use environment:

table 3

Group temperature

category

ⅡA、ⅡB、ⅡC

Methane, ethane, propane, styrene, benzene, toluene, xylene, acetone, carbon monoxide, phenol, cresol, dichloroethylene, chlorobenzene, ammonia, propyne, acrylonitrile, hydrogen cyanide, coke oven gas, hydrogen Wait

Butane, cyclopentane, propylene, ethylbenzene, isopropylbenzene, methanol, ethanol, propanol, butanol, cyclohexanone, methyl formate, ethyl acetate, dichloroethane, vinyl chloride, methylamine, Ethylene, acetylene, etc.

Pentane, hexane, cyclohexane, turpentine, naphtha, petroleum, kerosene, fuel oil, gasoline, pentanol, hexanol, chlorobutane, dimethyl ether, crotonaldehyde, etc.

Ethyl methyl ether, acetaldehyde, dibutyl ether, diethyl ether

Note: This table is quoted from Appendix B of GB3836.1—2000 “Electrical Equipment for Explosive Gas Environments Part 1: General Requirements”.

Explosion-proof electrical equipment selection principle

2.1 GB3836.15-2000 "Electrical Equipment for Explosive Gas Atmospheres Part 15: Electrical Installations for Hazardous Locations (Excluding Coal Mines)" provides three selection principles for explosion-proof electrical equipment:

(1) According to the classified hazardous area selection, it can be divided into 0 zone, 1 zone, and 2 zone equipment.

Zone 10 equipment: A single intrinsic safety "ia" class. Explosion-proof electrical appliances with other explosion-proof types cannot be used in zone 0.

21 zone equipment: Meet the requirements of one or more types of explosion-proof type such as explosion-proof "d", encapsulated "m", intrinsically safe "i", oil-impregnated "o", and increased safety "e" equipment.

32-zone equipment: Equipment for zones 0 and 1 and electrical equipment of type "n" and special type "s" according to IEC 6007-15.

(2) Select the ignition temperature based on the gas or vapor

Electrical equipment shall be sized for the highest surface temperature of any gas or vapour at the ignition temperature (Table 1)

(3) Selection according to gas type

The type of gas should be considered in the electrical equipment with explosion-proof “d” and intrinsically safe “i”, and the gas category and the electrical category should be in accordance with Table 4.

Table 4 Relationship between gas/vapor classification and equipment category

Gas/Vapor classification	Equipment classification
ⅡA	ⅡA、ⅡB or ⅡC
ⅡB	ⅡB、ⅡC
ⅡC	ⅡC