Selection Guide for Explosion-proof Weighbridges in Zone 1/2 Gas Atmospheres & Zone 21/22 Dust Atmospheres
When selecting explosion-proof weighbridges for hazardous explosive environments, it is essential to confirm the specific type of on-site explosive atmosphere, explosion-proof grade, explosion-proof type, temperature class, and other core parameters.
Division of Explosion-proof Zones
Gas hazardous areas are classified into Zone 0, Zone 1, and Zone 2; dust hazardous areas are classified into Zone 20, Zone 21, and Zone 22. Explosion-proof electrical equipment for different atmospheres cannot be mixed for use. Gas-explosion-proof devices are not applicable directly in dust-hazardous areas. For special sites with coexisting flammable gas and combustible dust, products with dual-environment explosion-proof certification are mandatory.
Hazard Classification Grade
The higher the hazard level of the area, the stricter the requirements for explosion-proof equipment. Zone 0 has the most stringent requirements, followed by Zone 1 and Zone 2 in sequence. Equipment certified for Zone 0 can be used in Zone 1; equipment certified for Zone 1 applies to Zone 2.
- Gas atmosphere explosion-proof grades: Ga, Gb, Gc (Priority: Ga＞Gb＞Gc)
- Dust atmosphere explosion-proof grades: Da, Db, Dc (Priority: Da＞Db＞Dc)
Applicable Explosion-proof Types
| Gas Atmosphere | Dust Atmosphere |
| Zone 0: Only Ex ia, ma type. Zone 1: Ex d, ib, e, p type. Zone 2: Ex ic, n type, and all higher-level explosion-proof types | Zone 20: Only Ex tD Da type; Db/Dc are prohibited. Zone 21: Ex tD Db type. Zone 22: Both Ex tD Db and Dc types are acceptable |
Characteristics of Explosive Substances
- Medium classification: Class II gas / Class III dust
- Gas group ranking: ⅡA＜ⅡB＜ⅡC (ⅡC is the strictest standard, suitable for hydrogen, acetylene, and other extreme hazardous gases)
- Dust category: Conductive dust, combustible dust, fibrous dust
Temperature class: T1 ~ T6 (T6 is the optimal grade)
T1=450℃, T2=300℃, T3=200℃, T4=135℃, T5=100℃, T6=85℃
Lower surface ignition temperature means higher safety performance.
Ingress Protection Grade: IP grade ≥ IP65 for dust environments and outdoor application scenarios.
All explosion-proof electrical appliances used in hazardous areas must be fully matched in explosion-proof grade, explosion-proof type, temperature class, and sealing grade.
| Hazardous Zone | Explosion-proof Type | Dc Grade Medium and Temperature Class | Explosion-proof Grade | Typical Explosion-proof Mark |
| Gas Zone 0 | Ex ia, ma, s | Class ⅡA/ⅡB/ⅡC (ⅡC is the strictest)T1~T6(T6 features the lowest surface temperature and highest safety level) | High (Ga) | Ex iaⅡC T6 Ga |
| Gas Zone 1 | Ex d, ib, e, p | Medium (Gb) | Ex dbⅡC T6 Gb | |
| Gas Zone 2 | Ex ic, n & full series | Low (Gc) | Ex icⅡC T6 Gc | |
| Dust Zone 20 | Ex tD | Class ⅢA/ⅢB/ⅢCIngress Protection Grade:≥IP65 for dust hazardous areas≥IP65 for outdoor installation | High (Da) | Ex iaⅢC T200 130℃ DaEx tD Da IP65 T130℃ⅢC |
| Dust Zone 21 | Ex tD | Medium (Db) | Ex tD ⅢC T80℃ Db(200A) | |
| Dust Zone 22 | Ex tD | Low (Dc) | Ex tD Dc |
Core Configuration of Explosion-proof Weighbridge
When the weighbridge body is installed in hazardous areas, three key components are required: an intrinsic safety explosion-proof load cell, an intrinsic safety explosion-proof junction box, and flame-retardant signal cable.
If the weighing indicator is placed in hazardous areas, a flameproof enclosure type weighing indicator or flameproof weighing controller shall be adopted. Safety barriers must be equipped at sensor interfaces inside the flameproof box.
1. Intrinsic Safety Explosion-proof Load Cell
Dual gas & dust explosion-proof sensors with Ex ia grade are recommended.
Typical marks: Ex iaⅡC T4 Ga, Ex iaⅢC T200 130℃ Da (applicable for all gas Zone 0/1/2 and dust hazardous areas)
Technical Parameters:
- Accuracy: 0.02%, OIML C3 grade
- Allowable overload: 125%; Ultimate overload: 150%
- Ingress Protection: IP68
2. Intrinsic Safety Explosion-proof Junction Box
Adopt dual gas & dust explosion-proof accessories of Ex ia grade.
Typical marks: Ex ia IIC T6 Ga, Ex iaⅢC T200 80℃ Da
Applicable for installation in Zone 0,1,2 hazardous areas.
3. Flameproof Enclosure Weighing Indicator / Controller
The enclosure is made of cast aluminum with a plastic-sprayed surface or a welded, sealed metal structure with surface spraying. It is fitted with a tempered glass display window and explosion-proof operation buttons on the front panel. Special certified safety barriers are installed at sensor ports inside the box to convert non-intrinsic safety interfaces into intrinsic safety ones. Flameproof cable glands are equipped at the bottom for connecting the power supply and flame-retardant signal cables.
- Ingress Protection Grade: IP66
- Common explosion-proof grades:
- Ex dbⅡB T6 Gb, Ex dbⅡC T6 Gb, Ex tb ⅢC T80℃ Db(200A)
- Ex dbⅡB T4 Gb, Ex dbⅡC T4 Gb, Ex tb ⅢC T130℃ Db(630A)
Application Scope
The explosion-proof weighbridge body can be deployed in Gas Zone 0/1/2 and Dust Zone 20/21/22.
Flameproof box-type weighing indicators are suitable for Gas Zone 1/2 and Dust Zone 21/22.
BINCEN explosion-proof weighbridges are fully applicable for overall installation in Gas Zone 1, Zone 2 as well as Dust Zone 21, Zone 22.
