Electrical equipment protection methods in GB/T3836 system
| Standard number | International abroad Corresponding standards | Explosion-proof type | Explosion-proof principle | Graphical method |
| GB/T 3836.1 | IEC60079-0 EN60079-0 FM3600 UL2279 | General requirements | ____ | ____ |
| GB/T 3836.2 | IEC60079-1 EN60079-1 FM3600 UL2279 | Explosionproof type “d” | When the equipment is in normal operation, the components that can generate spark arcs are placed in a flameproof enclosure. The flameproof enclosure can withstand the internal explosion pressure without loss and prevent it from spreading outside the enclosure. | 
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| GB/T 3836.3 | IEC60079-7 EN60079-7 FM3600 UL2279 | Increased safety type “e” | During normal operation, arcs, sparks and dangerous high temperatures will not be generated, and further structural protection measures will be taken to improve the safety of the equipment. | 
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| GB/T 3836.4 | IEC60079-11 EN60079-11 FM3601 UL2279 | Intrinsically safe “i” | Under specified conditions, the electrical sparks and thermal effects generated by the circuit inside the equipment during normal operation or specified fault conditions cannot ignite explosive mixtures. | 
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| GB/T 3836.5 | IEC60079-2 EN60079-2 FM3620 NFPA496 | Positive pressure type “P” | Keep the pressure of the internal protective gas higher than the surrounding environment to prevent explosive mixtures from entering the enclosure, or allow sufficient protective gas to pass through the enclosure to reduce the concentration of the explosive mixture inside to below the lower explosion limit. | 
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| GB/T 3836.6 | IEC60079-6 EN60079-6 FM3600 UL2279 | Liquid immersion type “O” | Immerse all components of electrical equipment in protective fluid so that the equipment cannot ignite explosive gases on the liquid surface or outside the enclosure. | 
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| GB/T 3836.7 | IEC60079-5 EN60079-5 FM3600 UL2279 | Sand filled type “q” | An explosion-proof type of electrical equipment in which fixed conductive parts that can ignite explosive gases are completely buried in the filling material to prevent ignition of the external explosive gas environment. | 
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| GB/T 3836.8 | IEC60079-15 EN60079-15 UL2279 | “n”type | Electrical equipment cannot ignite surrounding explosive gases (under normal working conditions and under determined abnormal working conditions). | 
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| GB/T 3836.9 | IEC60079-18 EN60079-18 FM3600 UL2279 | Pouring type”m” | The part that may ignite the explosive mixture is sealed in the compound so that it cannot ignite the surrounding explosive gas. | 
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| GB/T 3836.31 | IEC60079-31 EN60079-31 | Anti-dust ignite shell “t” | Electrical equipment used in explosive dust environments protected by enclosures to prevent dust ingress and limit surface temperatures. | 
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Classification of hazardous locations for electrical equipment used in explosive gas environments
| Zone 0 | Zone 1 | Zone 2 |
| Places where explosive gas environments appear continuously or exist for a long time. | Places where explosive gas environments may occur during normal operation. | During normal operation, it is impossible for an explosive gas environment to occur. If it does occur, it will only occur occasionally and only for a short period of time. |
Examples of explosion-proof signs for electrical equipment used in explosive gas environments
| Ex | db | [iaGa] | llB | T6 | Gb |
| EX symbol | Explosion proof type symbol | Intrinsically safe related equipment | Category symbol | Temperature group | EPL protection level |
Maximum surface temperature grouping of Class Il electrical equipment
| Temperature group | Maximum surface temperature of equipment (℃) |
| T1 | 450 |
| T2 | 300 |
| T3 | 200 |
| T4 | 135 |
| T5 | 100 |
| T6 | 85 |
Explosive gas classification group
| Electrical equipment categories | Representative gas | Gas classification | Maximum Test Safety Gap (MESG) | Minimum ignition current (MIC) |
| Category I | Methane (biogas) | — | — | |
| Class IIA | propane | A | MESG>0.9mm | MIC ratio>0.8 |
| Class IIB | Ethylene | B | MESG0.5mm~0.9mm | MIC ratio: 0.45~0.8 |
| Class IIC | Hydrogen/acetylene | C | MESG<0.5mm | MIC ratio<0.45 |
Note: Category I: Electrical equipment for underground coal mines (methane); Category Il: Electrical equipment for factories (other explosive gas environments except coal mines);
*: Only applicable to Class Il explosion-proof “d” intrinsically safe “i” electrical equipment and some “n” type equipment.
Categories and temperature groups of explosive gases or vapors
| Temperature group | T1 | T2 | T3 | T4 | T5 | T6 | |||
| category | I | Methane | — | ||||||
| IIA | acetic acid acetone Acetonitrile Allyl fluoride ammonia aniline Phenethane benzene Methyl styrene trimethylbenzene Pen-2-one (Methyl propyl ketone) | Cresol Ethyl bromide Isobutane Butyryl fluoride Methyl chloride propane Ethyl chloride oil Nitrogen (miscellaneous) benzene | cyclopentane Methylcyclopentane propionic acid Acetylene Methanol Methyl formate Ethyl acetate Ethylene oxide diisopropyl ether | Propanol Cyclohexanone Ethylene Furans Butane Methylamine Chlorohydrin Ethyl acrylate | Pentane Methylcyclohexane Petroleum (including gasoline) diesel fuel kerosene hexane Ethyl mercaptan Pentanol Chlorobutane Tetrahydrothiophene | Acetaldehyde | Ethyl nitrite | ||
| IIB | Propylene (methyl acetylene) Cyclopropane Acrylonitrile | hydrogen cyanide coke oven gas | Butadiene-1,3 Ethylene oxide Methyl acrylate Furans | Diformaldehyde Methylhydrofuranmethanol Crotonaldehyde Ethyl mercaptan | Ethyl methyl ether Diethyl ether Dibutyl ether Tetrafluoroethylene | ||||
| IIC | Hydrogen | Acetylene | — | Carbon disulfide | |||||
Electrical equipment for explosive dust environments
| District 20 | District 21 | District 22 |
| Places where explosive dust environments in the air appear continuously in the form of dust clouds for a long time or occur frequently. | Places where explosive dust environments in the air may appear or occasionally appear in the form of dust clouds during normal operations. | During normal operation, explosive dust rings in the air It is a place where it is impossible to appear in the state of a dust cloud, and if it appears, it will only exist for a short period of time. |
Examples of explosion-proof markings for electrical equipment used in explosive dust environments
| Ex | tb | lllC | T80°C | Db |
| Ex symbol | Explosion-proof type symbol | Category symbol | Maximum surface temperature T | EPL protection level |
Traditional correspondence between equipment protection levels (EPL) and zones
| Equipment protection level/area | Ga/Zone 0 | Gb/1 area | Gc/Zone 2 |
| The protection requirements stipulated for the equipment are based on the possibility of the equipment becoming an ignition source and the different characteristics of explosive gas environments and explosive dust environments protection level. | Equipment for use in explosive gas atmospheres, with a “very high” level of protection, is not a source of ignition during normal operation, expected failure or rare failure. | Equipment for use in explosive gas atmospheres, with a “high” level of protection, which is not a source of ignition under normal operation or expected failure conditions. | Equipment used in explosive gas environments has a “general” protection level and is not a source of ignition during normal operation. Some additional protective measures can also be taken to ensure that effective ignition will not occur when the ignition source is expected to occur (such as the failure of a lamp) ignite. |
| Da/20 area | Db/Area 21 | Dc/District 22 | |
| Equipment for use in explosive dust atmospheres, with a “very high” level of protection, is not a source of ignition during normal operation, anticipated failures or rare failures. | Equipment for use in explosive dust atmospheres, with a “high” level of protection, is not a source of ignition under normal operation or expected failure conditions. | Equipment used in explosive dust environments has a “general” protection level and is not an ignition source during normal operation. Some additional protective measures can also be taken to ensure that effective ignition will not occur when the ignition source is expected to occur (such as the failure of a lamp)ignite. |
Equipment protected by dust ignition resistant enclosure
| Class IIIA | Class IIIB | Class IIIC |
| he explosive environment in the air is a place where flammable flying catkins are present | Places where the explosive environment in the air is non-conductive dust | Places where the explosive environment in the air is conductive dust |
Equipment category and protection level
| protection level | Class IIIC | Class IIIB | Class IIIA |
| “ta” | IP6X | IP6X | IP6X |
| “tb” | IP6X | IP6X | IP5X |
| “tc” | IP6X | IP5X | IP5X |
