preface
Differences in the division of sites
Classification of hazards
Gas group
Temperature class
Differences in protection methods
Differences in installation methods
The two systems are marked in contrast
The standards of the two systems are compared
Differences in the division of sites
Classification and grouping of explosive substances (by the nature of combustible substances)
NEC system: Divided into three categories and seven groups:
Class I: Explosive gas Group A (acetylene),
Group B (hydrogen),
Group C (ethylene and related substances),
Group D (Propane and Alcohol products)
Class II: Explosive dust
Group E (Metal dust)
Group F (pulverized coal)
Group G (Grains and non-metallic dust)
Class III: Explosive Floc (not regrouped)
Classification and grouping of explosive substances (by the nature of combustible substances)
GB system: is divided into two categories and three groups:
Explosive gas
Group C (acetylene and hydrogen),
Group B (ethylene and similar substances)
Group A (propane and similar substances),
Combustible dust (not regrouped)
Classification of explosive hazardous sites
NEC system: Divided into two levels (Division1, Division 2)
Class 1 (Division 1): Places where explosive gases, dust, and Floc (accumulated to prescribed concentrations) may always or sometimes be present under normal working conditions.
Division 2: Places where explosive gases, dust, and Floc are unlikely to be present under normal working conditions.
GB system: Three zones (Zone 0/Zone20, Zone1/Zone21 Zone2/Zone22)
Zone 0: An area where explosive gases and vapors (concentrated to a specified concentration) exist continuously or for a long time under normal operating conditions.
Zone 1 (Zone 1/Zone21): An area where explosive gas & vapor/combustible dust (concentrated to specified concentrations) is likely to exist under normal operating conditions.
Zone 2 (Zone 1/Zone22): Under normal operating conditions, the presence of explosive gases & vapors/combustible dust (concentrated to specified concentrations) is unlikely.
Two system protection methods and scope of application
It can be seen from the data comparison in the previous table that the GB system allows a more significant gap value. This is also because although the principle of the explosion-proof type is the same, the clearance requirements differ.
In addition, the NEC system and explosion-proof devices are not allowed to be installed directly but must be wired with steel pipes, which also enhances the safety of the NEC system explosion-proof devices that can be used in Class 1 sites.
2. Intrinsically safe
In the NEC system, intrinsically secure corresponds to inherently secure ia in the GB system.
In the NEC system, there is no intrinsically safe ib; In the GB system, it is only used in zone 1.
In terms of structural requirements, it is equivalent to no incentive Circuits and no incentive Components in NEC systems.
3. Enhanced safety type
In the NEC system, there is no such protection.
4. No spark type
In the NEC system, there is no such protection.
5. Pouring and sealing type
This method is used only for partial or component protection in the NEC system.
6. Special Type
In the NEC system, there is no such protection.
NEC system Level 1: ia&p steel pipe wiring + seal and accessories in line with Level 1 requirements); Metal sheathed MI cable. Level 2: steel pipe wiring Metal-sheathed MI cable British system | GB system Zone 1: cable wiring or steel pipe wiring (sealing accessories, etc.). Zone 2: Cable or steel pipe wiring. Metric system |
NEC System: Class I, Group B,C,D
GB system: ExdIIB T4
According to NEC-1996 (505), the North American security system gradually adopted the regional system, with its logo AExdIIB T4, denoted by A as the regional system of the United States.
GB System NEC(505) NEC System *
GB3836.1 ANSI/UL 60079-0
GB3836.2 ANSI/UL 60079-1 UL1203
GB3836.3 ANSI/UL 60079-7
GB3836.4 ANSI/UL 60079-11 UL913
.
.
* In the North American Standard System, explosion-proof product standards are categorized by specific product categories, such as ANSI/UL894 (Hazardous Place switch), while the GB standard system is categorized by explosion-proof type. The explosion-proof product standard in the NEC system stipulates both the requirements of an explosion-proof structure and the product performance requirements related to explosion-proof safety.