**1. Division of Explosive Gas Hazardous Areas**
Explosive hazardous areas are classified differently across countries and regions, based on their specific safety standards. In China, the classification of explosive gas environments is divided into three zones—Zone 0, Zone 1, and Zone 2—based on the frequency and duration of explosive gas mixtures. This classification aligns with the international standard set by the International Electrotechnical Commission (IEC).
- **Zone 0**: This is an area where explosive gas mixtures are continuously present or occur for long periods under normal operating conditions. It is typically found in sealed containers, such as inside storage tanks or other enclosed gas spaces.
- **Zone 1**: This zone refers to an environment where explosive gas mixtures may be present during normal operation. Although it is a high-risk area, it is less common in real-world applications.
- **Zone 2**: This is the most common classification, where explosive gas mixtures are not expected to occur during normal operations, but may appear briefly under abnormal conditions.
In practical design scenarios, Zone 0 is rare, and even Zone 1 is seldom encountered. Most installations fall under Zone 2, which requires careful consideration of explosion-proof measures.
**2. Classification of Explosion-Proof Electrical Equipment**
Explosion-proof electrical equipment is generally divided into two main categories:
- **Class I**: Designed for use in underground coal mines, where the risk of methane gas explosions is significant.
- **Class II**: Used in non-mining environments, such as chemical plants, refineries, and other industrial settings where flammable gases may be present.
**1.3 Class II Equipment Categories**
Class II equipment is further subdivided into three types based on the maximum test safety gap (MESG) or minimum ignition current ratio (MICR):
- **IIA**: For gases with higher ignition energy, such as propane.
- **IIB**: For more easily ignitable gases like ethylene.
- **IIC**: For highly explosive gases such as hydrogen and acetylene.
Additionally, these devices are categorized into six temperature groups (T1–T6), based on their maximum surface temperature, ensuring they do not exceed the ignition temperature of the surrounding gas mixture.
**1.4 Gas Grouping by Ignition Temperature**
Explosive gas mixtures are also grouped according to their ignition temperature, which helps determine the appropriate type of explosion-proof equipment required for safe operation in different environments.
**1.5 Classification Based on Safety Clearance and Ignition Current**
The classification of explosive gases is primarily determined by their maximum test safety clearance (MESG) or minimum ignition current ratio (MICR), which indicates the level of risk associated with each gas.
**Features of Explosion-Proof Junction Boxes**
- **Durable Construction**: The junction box features a cast aluminum alloy shell with a powder-coated finish for an attractive appearance. Alternatively, it can be made from corrosion-resistant glass fiber-reinforced unsaturated polyester resin or stainless steel, providing excellent protection in harsh environments.
- **Easy Access**: The cover can be opened by loosening the bolts by one-third and then rotating the cover clockwise by 10 degrees, ensuring that the bolts remain secure while allowing quick access.
- **Flexible Wiring Options**: Multiple inlet and outlet configurations are available, including various thread types. Custom threading is also possible to meet specific installation requirements.
- **Wiring Compatibility**: The junction box supports both steel pipe and cable wiring, offering versatility for different application needs.
These features make the explosion-proof junction box a reliable and practical solution for use in potentially hazardous environments.
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