This summary is primarily divided based on the equipment application category, temperature classification of explosive gas mixtures, and explosion-proof protection types.

1. Equipment Application Category

Explosive electrical equipment is classified by type as follows:

Category I: Electrical equipment for underground coal mines

Category II: Electrical equipment for all explosive gas environments except underground coal mines

Category III: Electrical equipment for explosive dust environments except coal mines

Category II electrical equipment is further subdivided:

IIA: Representative gas is propane, with a relatively low explosive level.

IIB: Applicable to the operating conditions of Category IIA equipment, with a medium explosive level; representative gas is ethylene.

IIC: Applicable to the operating conditions of Category IIA and IIB equipment, with the highest explosive level; representative gases are hydrogen and acetylene.

For Category III electrical equipment, it is classified by dust type:

IIIA: Combustible dust clouds

IIIB: Non-conductive dust

IIIC: Conductive dust

2. Temperature Classification of Explosive Gas Mixtures

Temperature classification is divided based on differences in the ignition temperature of explosive gas mixtures, as shown below:

T1: t<450°C

T2: 200° C<t≤300 ° C

T3: 135° C<t≤200° C

T4: 100° C<t≤135°C

T5: 85° C<t≤100° C

T6: t≤85°C

3. Explosion-Proof Protection Types

Explosion-proof protection types are designed for different purposes and environments, primarily including:

d: Flameproof enclosure

e: Increased safety

i: Intrinsic safety

m: Encapsulation

n: Type n

o: Oil-immersed

p: Pressurized enclosure

q: Sand-filled

s: Special type

t: Dust ignition-proof enclosure

4. Example of Ex Certification Marking

Taking the explosion-proof mark Ex db IIB T4 Gb as an example, its meaning is:

Ex: Indicates that the equipment is an explosion-proof equipment.

db: Indicates that the equipment is of flameproof enclosure type.

IIB: Indicates that the explosive gas environment for the equipment is Category IIB, with the representative gas being ethylene.

T4: Indicates that the maximum surface temperature group of the equipment does not exceed 

135°C (T4).

Gb: Indicates the equipment protection level, with a high protection grade.

In summary, the division of explosion-proof protection grades is a comprehensive consideration process, which needs to integrate multiple factors such as equipment application category, temperature group of explosive gas mixtures, and explosion-proof protection type. In practical applications, the appropriate explosion-proof protection grade and equipment should be selected according to the specific explosive environment and equipment requirements.

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