Electric motors, electrical appliances, and instrument products used in explosive hazardous environments in petroleum, chemical, military, pharmaceutical, and other enterprises can generate arcs, sparks, and dangerous high temperatures during normal operation. Once the concentration of combustible mixtures in the environment reaches the explosive limit range, it will cause explosions in the surrounding environment. Therefore, these electrical products are designed as explosion-proof electrical equipment.
The design scheme of explosion-proof electrical products should generally consider the following aspects:

1、 Determine the explosion-proof type of the product

In explosion-proof electrical engineering design projects, the level of explosion hazard, the level and temperature group of explosive mixtures in which electrical equipment is located are marked. According to the GB3836.15-2010 standard, the explosion-proof type of electrical equipment must be suitable for the explosion hazard area.
1The explosion-proof types of electrical equipment suitable for hazardous environments in Zone 0 include: ia, s

Among them: ia - Intrinsically safe ia level

S-Explosion proof special type
2The explosion-proof types of electrical equipment suitable for hazardous environments in Zone 1 include: ia, ib, d, e (partial), m, p, o, q

Among them: ib - Intrinsically safe IB level

D - Explosion proof type

E - Increased safety type

M - Pouring and sealing type

P-Positive pressure type

O - Oil filled type

Q - Sand filled mold

Note: The use of increased safety electrical equipment in Zone 1 environments is limited to explosion-proof junction boxes, three-phase squirrel cage asynchronous motors, and single pin fluorescent lamp products.
3The explosion-proof types of electrical equipment suitable for hazardous environments in Zone 2 include all explosion-proof types and n-type electrical equipment in Zone 0 and Zone 1 environments.

Among them: n - includes non spark type, spark type, energy limiting equipment, non ignition components, restricted breathing type, simple positive pressure type and other explosion-proof structural measures that take explosion-proof measures for spark contacts.

If some explosion-proof instruments are used in two hazardous environments at the same time, the explosion-proof design of the instruments should comply with the respective hazardous areas where they are installed. For example, for a liquid level sensor installed in a petroleum liquid tank, its probe body is located in zone 0, and the junction box or on-site measuring instrument is located in zone 1. The probe body should be designed as cost, quality, and safety (IA level), and the junction box or on-site measuring instrument should be explosion-proof.

 2、 Determine the type, explosion-proof level, and temperature group of the product

1Explosion proof electrical equipment is divided into two categories: Class I and Class II

Class I - Mining Electrical Equipment

Class II - Electrical Equipment for Factory Use

Class II electrical equipment is further divided into three levels: IIA, IIB, and IIC. They are classified according to the maximum non explosive gap and the minimum ignition current ratio.

Explosion proof electrical products of Class IIC, suitable for Class IIC, IIB, and IIA combustible gases

Explosion proof electrical products of Class IIB, suitable for Class IIB and IIA combustible gases

Explosion proof electrical products of Class IIA, suitable for Class IIA combustible gases  

2Explosion proof electrical equipment is divided into six temperature groups T1-T6, which are determined according to the highest surface temperature of the equipment in Table 1.

Electrical equipment in the T6 temperature group can be used for combustible gases in the T1, T2, T3, T4, T5, and T6 temperature groups, while electrical equipment in the T5 temperature group can be used for combustible gases in the T1, T2, T3, T4, and T5 temperature groups, and so on. 

3、 Consider the usage environment of explosion-proof products

The structure and materials of explosion-proof electrical equipment should be able to withstand the effects of chemical corrosion, sunlight, rain, humidity, and vibration in the environment. They can be designed as outdoor, anti-corrosion, seismic, and humidity resistant explosion-proof electrical products, respectively

For fuel dispenser equipment installed at gas stations, the sealing material of the electrical equipment and the sheath of the wiring cables should be made of oil resistant rubber products or polyvinyl chloride sheathed cables to extend the service life of the products.

Outdoor explosion-proof electrical equipment should increase the protection level of the equipment casing or add sunscreen barriers. A light colored layer can effectively reduce the surface temperature of the device.

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