Division of hazardous areas

According to the length of time the hazardous substances exist in the site, the hazardous sites under two types of different states are divided into three zones, namely, zone 0, zone 1 and zone 2 for explosive gas environment, zone 20, zone 21 and zone 22 for combustible dust environment.
For explosive gas environment, GB 3836.14 - 2021 standard stipulates:
Zone 0: The explosive gas environment appears continuously or exists for a long time.
Zone 1: In normal operation, where explosive gas atmosphere may occur.
Zone 2: In normal operation, it is impossible to have an explosive gas environment. If it occurs, it will happen occasionally and only exist for a short time.
Here, "normal operation" refers to the normal start-up, operation, parking, loading and unloading of flammable substances, opening and closing of the closed container cover, safety valve, discharge valve and all plant equipment are working within its design parameters.

Analysis of Explosion-proof Signs

Explosion-proof electrical equipment shall comply with the requirements of GB 3836. The contents of explosion-proof marks for explosion-proof electrical equipment shall include:
Explosion-proof type Equipment category Gas group Temperature group 1. Explosion-proof type

2. Equipment category
Electrical equipment for explosive gas environments is divided:
Class I: underground coal mine electrical equipment;
Class II: Electrical equipment for plant use
Class II flameproof "d" and intrinsically safe "I" electrical equipment is further divided into classes IIA, IIB, and IIC.
3. Gas group
The explosive transmission capacity of explosive gas mixture marks the degree of explosion danger. The greater the explosive transmission capacity of explosive mixture, the higher the risk. The explosive transmission capacity of explosive mixtures can be expressed by the maximum test safety clearance. At the same time, the degree of difficulty of explosive gas, liquid vapor and mist being ignited also marks the degree of explosion danger, which is expressed by the minimum ignition current ratio. Class II flameproof electrical equipment or intrinsically safe electrical equipment is further divided into classes IIA, IIB and IIC according to its maximum test safety clearance or minimum ignition current ratio applicable to explosive gas mixtures. as shown in the following table.

4. Temperature group
The ignition temperature of an explosive gas mixture is the temperature limit at which ignition can take place.
Electrical equipment is divided into T1 ~ T6 groups according to its maximum surface temperature, so that the maximum surface temperature of the corresponding T1 ~ T6 group of electrical equipment can not exceed the allowable value of the corresponding temperature group. The relationship between temperature groups, equipment surface temperature and ignition temperature of flammable gas or steam is shown in the following table: