Here's a detailed comparison of explosion-proof classifications for AGVs (Automated Guided Vehicles) in gas and dust environments, covering China (GB standards), Europe (ATEX/IEC), and North America (NEC/CEC):
1. Gas Atmospheres Classification
(1) China (GB 3836 Standard)
- Hazardous Area Classification:
○ Zone 0: Explosive gas mixture present continuously or for long periods (e.g., inside gas pipelines).
○ Zone 1: Gas likely to occur occasionally (e.g., during equipment leaks).
○ Zone 2: Gas unlikely or present only briefly (e.g., accidental rupture).
- Gas Groups:
○ IIA (e.g., propane), IIB (e.g., ethylene), IIC (e.g., hydrogen, most stringent).
- Temperature Classes: T1 (≤450°C) to T6 (≤85°C).
(2) Europe (ATEX/IEC 60079)
- Zoning: Identical to China (Zone 0/1/2), but labeling differs:
○ Example: II 2G Ex db IIB T4 Gb
△ 2G = Zone 1 (gas environment).
(3) North America (NEC/CEC)
- Two Systems:
○ Class/Division System (Legacy):
△ Class I: Gases.
△ Division 1: Gas present normally (similar to Zone 0/1).
△ Division 2: Gas rare/short-lived (similar to Zone 2).
○ Zone System (IEC-aligned):
△ Zone 0/1/2, with Groups A-D (A: acetylene, B: hydrogen, C: ethylene, D: propane).
2. Dust Atmospheres Classification
(1) China (GB 12476 Standard)
- Hazardous Area Classification:
○ Zone 20: Dust cloud present continuously (e.g., silos).
○ Zone 21: Dust likely occasionally (e.g., during filling).
○ Zone 22: Dust unlikely/short-term (e.g., during cleaning).
- Dust Types:
○ Group III: Combustible dust (e.g., grain, coal, metal powders).
- Temperature Limits: Based on dust layer thickness (e.g., T90°C for ≤5mm dust layer).
(2) Europe (ATEX/IEC 61241)
- Zoning: Same as China (Zone 20/21/22). Example marking:
○ III 2D Ex tb IIIB T90°C Db
△ 2D = Zone 21 (dust environment).
△ IIIB = Non-conductive dust.
(3) North America (NEC/CEC)
- Class/Division System:
○ Class II: Combustible dust (e.g., flour, coal).
△ Division 1: Dust normally present (Zone 20/21).
△ Division 2: Dust rarely present (Zone 22).
○ Class III: Ignitable fibers (e.g., cotton, wood chips).
- Zone System (IEC-aligned):
○ Zone 20/21/22, with Groups E (metal), F (carbon), G (grain).
3. Key Differences: Gas vs. Dust
| Aspect | Gas Environments | Dust Environments |
|---|---|---|
| China Standard | GB 3836 (Zone 0/1/2) | GB 12476 (Zone 20/21/22) |
| IEC/ATEX | IEC 60079 (Zone 0/1/2) | IEC 61241 (Zone 20/21/22) |
| North America | Class I, Div 1/2 or Zone | Class II/III, Div 1/2 or Zone |
| Grouping Basis | Gas properties (IIA-IIC) | Dust type (IIIB/IIIC) |
| Typical Use | Oil refineries, gas pipelines | Grain processing, pharmaceuticals |
4. Design Implications for AGVs
- Gas Environments:
○ Prevent sparks/hot surfaces (e.g., flameproof "Ex d" or increased safety "Ex e").
- Dust Environments:
○ Prevent dust ingress/accumulation (e.g., IP6X enclosure, stricter surface temperature limits).
5. Certification Requirements
- China:
○ Gas: GB 3836 certification.
○ Dust: GB 12476 certification.
- Europe:
○ ATEX certification for both gas (2014/34/EU) and dust (1999/92/EC).
- North America:
○ Class II/III devices require UL/FM approval (Group E for metal dust is most stringent).
Summary
- Similar Zoning Logic: Zone 0/1/2 (gas) ↔ Zone 20/21/22 (dust), but different protection methods.
- North America's Legacy System: Class/Division adds granularity (Class II vs. III).
- Critical Differences:
○ Dust focuses on sealing and surface temperature.
○ Gas focuses on spark/arc prevention.
Recommendation: For AGVs in hybrid environments (e.g., chemical plants), dual certification (e.g., ATEX + IECEx or GB + NEC) is mandatory. Always consult certification bodies (e.g., CNEX, TÜV, UL) early in design.
