The North American Explosion Protection Certification System (NEC system) differs significantly from the GB system supported by China's national standard system in terms of classification and grouping of explosive substances, classification of hazardous areas, explosion protection methods, installation and wiring. Although the Electrical Installation Regulations (NEC) in the United States have gradually accepted the hazardous area classification system of the IEC60079 series standards (corresponding to the Chinese national standard GB3836 series) since the 1996 edition, and the product standards in the United States have also been revised and supplemented accordingly. However, for manufacturers of explosion-proof electrical products familiar with China's explosion-proof certification system and users in industries such as petrochemicals that widely use imported products, they still feel confused about the classification system in North America and the design and manufacturing requirements, installation and use, and reasonable selection of explosion-proof electrical products under China's explosion-proof certification system. Especially for some manufacturers who strive to enter the North American market, they are eager to understand the differences between the two standard systems on how to smoothly enter the North American market.
1、 Differences in venue division
1Classification and grouping differences of explosive substances
2Differences in zoning of explosive locations
3Differences in temperature groups
2、 Differences in protection methods
Protection methods and scope of application of North American NEC system and Chinese GB system
1. Explosion proof type
2. Intrinsic safety type
In the NEC system, the intrinsic safety type corresponds to the intrinsic safety type ia in the GB system.
In the NEC system, there is no intrinsic safety type ib; In the GB system, it is also limited to use in Zone 1.
In terms of structural requirements, it is equivalent to the "non induced circuits" and "non induced components" in the NEC system.
3. Enhanced safety: In the NEC system, this protection method is not available.
4. Spark free type: In the NEC system, this protection method is not available.
5. Sealing type: In the NEC system, this method is only used for local protection or component protection.
6. Special type: In the NEC system, this protection method is not available.
3、 Differences in installation methods
4、 Comparison of two major system symbols
NEC system: Class I, Division 1, Group C, T6
GB/IEC system: Ex d IIB T4
5、 Comparison of two major system standards
China/IEC explosion-proof system: GB3836 and IEC60079 series standards
NEC explosion-proof system: UL standard
Explanation: In the North American standard system, explosion-proof product standards are divided by specific types of products, such as ANSI/UL894 (switches for hazardous locations), while the GB standard system is divided by explosion-proof types The explosion-proof product standards in the NEC system not only specify requirements for explosion-proof structures, but also specify performance requirements for products related to explosion-proof safety
6、 Comparison between NEMA enclosure type rating and IP protection rating
NEMA: National Electrical Manufacturers Association of the United States
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