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 flammable mixtures in the environment reaches the explosive limit range, it will cause an explosion 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 the design project of explosion-proof electrical engineering, the level of explosion hazard zone, the level and temperature group of explosive mixture where the electrical equipment is located are all marked. According to the GB/T 3836.15-2017 standard, the explosion-proof type of electrical equipment should adapt to the explosion hazard zone.
1The explosion-proof types of electrical equipment suitable for hazardous environments in Zone 0 are: ia、s
Among them: ia - intrinsic safety type ia level
OP is - Intrinsically Safe Optical Radiation
Ma - Sealing type ma grade
SA - 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 - intrinsic safety type ib level
Db - Explosion proof type
EB - Increased Safety Type
MB - Sealed Type
Pxb, pyb - positive pressure type
Ob - Oil filled type
Qb - sand filling mold
Note: The use of increased safety electrical equipment in Zone 1 environment 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 in Zone 0 and Zone 1 environments, and n-type electrical equipment.
Among them: n - including spark free type, spark type with explosion-proof measures for spark contacts, energy limiting equipment, non igniting components, restricted breathing type, simple positive pressure type and other explosion-proof structural measures.
If some explosion-proof instruments are used in two hazardous environments at the same time, the explosion-proof design of the instruments should be in accordance with the hazardous areas where they are installed. For example, the liquid level sensor installed in the petroleum liquid tank should have its probe body located in Zone 0, and the junction box or on-site measuring instrument located in Zone 1. The probe body should be designed to be cost-effective and safe (IA level), and the junction box or on-site measuring instrument should be explosion-proof.
2、 Determine the type, explosion-proof rating, 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 divided into three levels: IIA, IIB, and IIC. They are classified according to the ratio of maximum non explosive gap and minimum ignition current.
Explosion proof electrical products of Class IIC, suitable for Class IIC, Class IIB, and Class IIA flammable gases
Explosion proof electrical products of Class IIB, suitable for Class IIB and Class IIA flammable gases
Explosion proof electrical products of Class IIA, suitable for Class IIA flammable 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.
| Temperature group |
Maximum surface temperature ° C |
| T1 |
450 |
| T2 |
300 |
| T3 |
200 |
| T4 |
135 |
| T5 |
100 |
| T6 |
85 |
Electrical equipment in the T6 temperature group can be used for flammable gases in the T1, T2, T3, T4, T5, and T6 temperature groups, while electrical equipment in the T5 temperature group can be used for flammable 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, sun exposure, rain, humidity, vibration, etc. in the environment. They can be designed as outdoor, anti-corrosion, shock resistant, humidity resistant and other explosion-proof electrical products
The sealing material of the electrical equipment and the sheath of the wiring cable of the fuel dispenser equipment installed at the gas station should be made of oil resistant rubber products or polyvinyl chloride sheathed cables, which can extend the service life of the product.
Outdoor explosion-proof electrical equipment should increase the protection level of the equipment casing or add sun protection barriers. Light colored layers can effectively reduce the surface temperature of equipment.
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