- What is ATEX Explosion-Proof Certification?
ATEX explosion-proof certification is a mandatory certification developed by the European Union for equipment and protective systems intended for use in potentially explosive atmospheres. “ATEX” is derived from the French term “ATmosphères EXplosibles,” meaning “explosive atmospheres” [1].
2. Importance of ATEX Certification
- Legal Requirement: Products sold or used in the EU market must obtain ATEX certification.
- Safety Assurance: Ensures that equipment will not trigger an explosion in hazardous environments.
- Market Access: An essential passport for entering the European market.
3. Introduction to ATEX Directives
ATEX certification is based on two main directives [2]:
- ATEX Product Directive (2014/34/EU): Specifies the technical requirements for equipment and protective systems.
- ATEX Workplace Directive (1999/92/EC): Defines the responsibilities of employers in explosive atmospheres.
4. ATEX Equipment Classification
ATEX classifies equipment into two groups [3]:
| Relationship between ATEX Zones and required equipment | ||||||
| ATEX Zone | Equipment | |||||
| Zone: a place in which an explosive atmosphere is.. | ATEX Zone | Level of protectionis assured in… | Category | Marking | ||
| Gases | Dusts | Gases | Dusts | |||
| continually present | 0 | 20 | the event of two faultsoccurring indepen- dently ofeach other | 1 | II 1G | II 1D |
| likely to occur in normaloperation occasionally | 1 | 21 | the event of oneequipment fault | 2 | II 2G | II 2D |
| not likely to occur in normaloperation and only for veryshort durations | 2 | 22 | normal operation | 3 | II 3G | II 3D |
- Category I: For mines and underground works
- M1: Can continuously operate in explosive atmospheres.
- M2: Power must be cut off in the event of an explosion.
- Category II: For other potentially explosive environments
- 1: Suitable for Zone 0 or Zone 20 (continuous explosive environment).
- 2: Suitable for Zone 1 or Zone 21 (possible explosive environment).
- 3: Suitable for Zone 2 or Zone 22 (unlikely or short-term explosive environment).
5. Detailed Classification of Hazardous Areas
In the ATEX system, hazardous areas are classified based on the frequency and duration of explosive atmospheres. These areas are divided into two main categories: gas environments (G) and dust environments (D). Understanding these classifications is essential for the correct selection and use of explosion-proof equipment [4][5].
5.1 Gas Hazardous Areas (G)
- Zone 0G: Where explosive gas atmospheres are present continuously, for long periods, or frequently.
- Zone 1G: Where explosive gas atmospheres may occasionally occur during normal operations.
- Zone 2G: Where explosive gas atmospheres are unlikely to occur during normal operations, and if they do, they will exist only for a short time.
5.2 Dust Hazardous Areas (D)
- Zone 20D: Where explosive dust atmospheres are present continuously, for long periods, or frequently in a cloud form.
- Zone 21D: Where explosive dust atmospheres may occasionally occur during normal operations.
- Zone 22D: Where explosive dust atmospheres are unlikely to occur during normal operations, and if they do, they will exist only for a short time.
5.3 Correspondence Between Area Classification and Equipment Category
ATEX directives classify equipment into different categories to match various hazardous areas. Below is the correspondence between area classification and equipment category:
| Hazardous Area | Applicable Equipment Category | Environment Type |
| Zone 0 | II 1G | Gas |
| Zone 1 | II 2G | Gas |
| Zone 2 | II 3G | Gas |
| Zone 20 | II 1D | Dust |
| Zone 21 | II 2D | Dust |
| Zone 22 | II 3D | Dust |
In this correspondence:
- “II” indicates non-mining equipment.
- Numbers “1,” “2,” and “3” represent protection levels, with “1” being the highest level.
- “G” represents gas environments.
- “D” represents dust environments.
6. Analysis of Explosion-Proof Protection Methods [6]
6.1 Flameproof Enclosure (Ex d)
Flameproof enclosure design focuses on the following key parameters and considerations:
- Maximum Experimental Safe Gap (MESG): Describes the maximum overpressure during an explosion under standard conditions.
- Explosion Pressure Endurance: Design must withstand the actual maximum explosion pressure compared to the reference pressure.
- Flame Propagation Path Control: Ensures that flames do not propagate inside the equipment, controlling the spread of the explosion.
6.2 Intrinsic Safety (Ex i)
Intrinsic safety design is based on energy limitation and is divided into different levels:
- ia Level: Allows two countable faults to occur simultaneously.
- ib Level: Allows one countable fault to occur simultaneously.
- ic Level: Remains safe during normal operation without special restrictions.
6.3 Increased Safety (Ex e)
Increased safety design focuses on reducing the following risks:
- Arcs, Sparks, and Hot Surfaces: These risks are reduced by improving insulation levels and mechanical protection.
- Creepage Distances and Clearances: Ensures adequate distances and protection to prevent arc formation.
- Temperature Rise Limits: Sets maximum temperature rise limits to avoid overheating that could cause fire or explosion.
- IP Protection Rating: Ensures the device’s resistance to water and dust, further enhancing safety.
7. Temperature Classifications and Gas Grouping
7.1 Temperature Classifications
Different temperature classifications apply to various environments and applications:
- T1: Maximum surface temperature 450°C.
- T2: Maximum surface temperature 300°C.
- T3: Maximum surface temperature 200°C.
- T4: Maximum surface temperature 135°C.
- T5: Maximum surface temperature 100°C.
- T6: Maximum surface temperature 85°C.
When selecting temperature classifications, environmental temperature impact, device self-heating, and safety factors (usually 5K-10K) should be considered.
7.2 Gas Grouping
Gas grouping is classified based on the Maximum Experimental Safe Gap (MESG) and Minimum Ignition Current (MIC) ratio:
- IIA: Propane, MESG > 0.9, MIC ratio > 0.8.
- IIB: Ethylene, MESG between 0.5 and 0.9, MIC ratio between 0.45 and 0.8.
- IIC: Hydrogen, MESG < 0.5, MIC ratio < 0.45.
These parameters are key indicators for determining the gas group and the suitability of explosion-proof equipment.
8. Interpretation of ATEX Explosion-Proof Markings
ATEX-certified products must carry specific markings, for example:
- Mark Interpretation:
- II: Equipment group, where II indicates suitability for environments other than mines.
- 3: Equipment category, where 3 indicates suitability for Zone 2 (for gases) or Zone 22 (for dust). Zone 2 is a less hazardous area where an explosive atmosphere is unlikely to occur in normal operation and, if it does occur, it will exist only for a short period.
- G: Indicates suitability for gas (G) environments.
- Ex ic: This indicates that the equipment has intrinsically safe (ic) protection. It limits the energy in the circuit to prevent ignition and is typically used for Zone 2 environments. This is different from Ex d (flameproof enclosure), which is a different form of explosion protection.
- IIb: Gas group, where IIb includes gases like ethylene. This group is less hazardous compared to IIC, which includes more dangerous gases like hydrogen and acetylene.
- T4: Temperature classification, where T4 indicates that the maximum surface temperature does not exceed 135°C. This is crucial to prevent ignition of gases in the environment.
- Gc: Equipment protection level, where Gc corresponds to a medium protection level suitable for Zone 2. This means that the equipment is designed to be safe even if an explosive atmosphere occurs occasionally.
IU-Plus Tech ATEX Explosion-Proof Rugged Tablet T71Ex specific : II 3G Ex ic IIb T4 Gc
9. ATEX Certification Process [7]
- Determine Product Category: Choose the appropriate equipment category based on the intended environment.
- Meet Basic Requirements: Ensure that the product design meets the basic health and safety requirements of the ATEX directive.
- Prepare Technical Documentation: Compile technical documentation containing product design, manufacturing, and operational information.
- Testing: Send samples or conduct on-site testing according to standards.
- Notified Body Involvement: For high-risk categories, a notified body must carry out conformity assessment and issue certificates.
- Declaration of Conformity: A written declaration of conformity must be issued.
10. Conclusion
ATEX explosion-proof certification is essential for ensuring the safe operation of equipment in potentially explosive environments. The ATEX directives not only set technical requirements for equipment and protective systems but also provide legal protection for products entering the European market. Proper understanding and compliance with ATEX standards can help reduce the risk of fire and explosion in industrial settings, ensuring personnel safety and reliable operation of equipment.
References
[1] European Commission. (2014). Directive 2014/34/EU of the European Parliament and of the Council. Official Journal of the European Union.
[2] European Parliament and Council. (1999). Directive 1999/92/EC. Official Journal of the European Communities.
[3] CEN. (2016). EN 60079-0:2012+A11:2013 Explosive atmospheres – Part 0: Equipment – General requirements.
[4] IEC 60079-10-1:2020 Explosive atmospheres – Part 10-1: Classification of areas – Explosive gas atmospheres
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