ATEX refers to the European Union regulations that govern the use of equipment and protective systems in environments where there is a risk of explosion due to the presence of flammable gases, vapors, or dust. The name ATEX comes from the French “ATmosphères EXplosibles,” meaning explosive atmospheres. ATEX certification ensures that equipment, including automation control panels, can be safely used in hazardous areas without triggering explosions.
What is ATEX?
ATEX is governed by two EU directives:
- ATEX 114 Directive (2014/34/EU): This directive applies to equipment and protective systems intended for use in potentially explosive atmospheres. It sets the essential health and safety requirements (EHSR) and conformity assessments for products.
- ATEX 153 Directive (1999/92/EC): This directive applies to the safety of workers in explosive atmospheres. It defines safety measures that employers must follow to protect employees working in hazardous areas.
ATEX zones classify hazardous areas based on the likelihood and duration of explosive atmospheres occurring. Equipment must be designed according to the specific zone it will be used in.
ATEX Zones and Categories
ATEX divides hazardous areas into zones based on the frequency and duration of the presence of explosive gases, vapors, or dust.
For Gas Atmospheres:
- Zone 0: An area where an explosive gas atmosphere is continuously present or present for long periods.
- Zone 1: An area where an explosive gas atmosphere is likely to occur occasionally during normal operation.
- Zone 2: An area where an explosive gas atmosphere is not likely to occur in normal operation, but if it does occur, it will exist for a short time.
For Dust Atmospheres:
- Zone 20: An area where an explosive dust atmosphere is continuously present or present for long periods.
- Zone 21: An area where an explosive dust atmosphere is likely to occur occasionally during normal operation.
- Zone 22: An area where an explosive dust atmosphere is not likely to occur in normal operation, but if it does occur, it will exist for a short time.
Equipment Categories:
- Category 1: Equipment for use in Zone 0 (gas) or Zone 20 (dust). These are areas with continuous or long-term explosive atmospheres.
- Category 2: Equipment for use in Zone 1 (gas) or Zone 21 (dust). These are areas where explosive atmospheres are likely to occur occasionally.
- Category 3: Equipment for use in Zone 2 (gas) or Zone 22 (dust). These are areas where explosive atmospheres are not likely to occur, and if they do, they last only for a short time.
Standards for ATEX-Certified Automation Control Panels
Automation control panels used in ATEX zones must adhere to specific standards that address the design, construction, and operation of equipment in hazardous areas. Below are key standards that apply to ATEX-certified automation control panels:
- EN 60079 Series (IEC 60079 International Equivalent)
- Description: The EN 60079 series of standards specifies the requirements for electrical equipment used in explosive gas and dust atmospheres. The series covers different protection methods, design considerations, and testing procedures.
- Key Parts:
- EN 60079-0: General requirements for equipment used in explosive atmospheres.
- EN 60079-1: Protection by flameproof enclosures (Ex d).
- EN 60079-2: Protection by pressurization (Ex p).
- EN 60079-7: Protection by increased safety (Ex e).
- EN 60079-11: Protection by intrinsic safety (Ex i).
- EN 60079-15: Protection by type of protection (Ex n) for Zone 2 equipment.
- Application: These standards ensure that automation control panels and electrical equipment are designed to prevent ignition, even when installed in potentially explosive environments. They specify protection techniques such as encapsulation, intrinsic safety, and pressurization to mitigate risks.
- EN 61439-1/2
- Description: This standard outlines the general rules and requirements for low-voltage switchgear and control gear assemblies, including control panels used in hazardous areas.
- Scope:
- Performance requirements
- Temperature rise
- Short-circuit strength
- Mechanical operation
- Application: This standard ensures that control panels are designed and tested to withstand normal operating conditions and faults while maintaining safety in hazardous areas.
- EN 13463 Series
- Description: The EN 13463 series applies to non-electrical equipment for use in explosive atmospheres. This is relevant for control panels that incorporate mechanical components (e.g., actuators or drives) that need ATEX compliance.
- Key Parts:
- EN 13463-1: Basic requirements for non-electrical equipment.
- EN 13463-5: Protection by constructional safety (Ex c).
- Application: These standards ensure mechanical parts within the control panel do not generate sparks or hot surfaces that could ignite an explosive atmosphere.
- EN 61241 (IEC 61241 International Equivalent)
- Description: This standard specifies requirements for electrical equipment used in areas where combustible dust is present. It includes guidance on minimizing the risks of dust explosions.
- Key Parts:
- EN 61241-0: General requirements for electrical apparatus for use in the presence of combustible dust.
- EN 61241-1: Protection by enclosures (Ex tD) for dust environments.
- Application: This is important for control panels installed in environments where dust could cause explosions, such as grain silos or flour mills.
Protection Methods for ATEX Control Panels
Automation control panels used in ATEX environments must be designed using one or more protection techniques to minimize the risk of explosion. Common ATEX protection methods include:
- Flameproof Enclosures (Ex d)
- Description: The control panel is housed in a flameproof enclosure that can contain any internal explosion without igniting the external explosive atmosphere. This is commonly used in Zones 1 and 2 for gas atmospheres.
- Application: Suitable for automation control panels in areas with potentially explosive gases, such as oil refineries or chemical plants.
- Increased Safety (Ex e)
- Description: Components within the safety equipment control panels are engineered with enhanced safety margins to prevent sparks or overheating, even in fault conditions. This design approach is frequently applied for equipment operating in Zone 1 and Zone 2 gas atmospheres.
- Application: Used for motor starters, lighting fixtures, and other components that need to operate safely in explosive environments.
- Intrinsic Safety (Ex i)
- Description: The energy available within the control panel circuits is limited to levels that are too low to ignite an explosive atmosphere. This method is used in Zones 0, 1, and 2, making it one of the safest protection methods.
- Application: Commonly used in control systems, measurement devices, and automation panels where low-energy signals are used.
- Pressurization (Ex p)
- Description: The control panel is pressurized with clean air or inert gas to prevent the ingress of explosive gases or dust. Any internal components that could cause ignition are kept in a safe atmosphere.
- Application: Used for large control systems, analyzers, and instrumentation enclosures in hazardous areas.
- Encapsulation (Ex m)
- Description: Critical components are encapsulated in resin or another material to prevent them from coming into contact with the explosive atmosphere. This method can be used for both gas and dust environments.
- Application: Suitable for sensors, transformers, or small control devices.
- Protection by Enclosure (Ex tD)
- Description: The control panel enclosure is sealed to prevent the ingress of combustible dust. The enclosure is designed to avoid overheating or sparks inside that could ignite the dust.
- Application: Used in industries where combustible dust is present, such as grain processing, woodworking, and food production.
ATEX Markings on Automation Control Panels
ATEX-certified control panels will display specific markings that provide detailed information about their certification and suitability for hazardous environments. Typical ATEX markings include:
- Ex: The equipment is certified for use in explosive atmospheres.
- II: Indicates non-mining equipment.
- G: Suitable for gas atmospheres.
- D: Suitable for dust atmospheres.
- 1, 2, or 3: The equipment’s category, indicating the level of protection and the zone where it can be used (e.g., 1 for Zone 0/20, 2 for Zone 1/21, 3 for Zone 2/22).
Example of ATEX marking for a control panel:
- Ex II 2G Ex d IIB T4:
- Ex: Equipment certified for explosive atmospheres.
- II: Non-mining equipment.
- 2G: Equipment suitable for use in Zone 1 (gas).
- Ex d: Protection method is flameproof.
- IIB: Gas group classification.
- T4: Maximum surface temperature of equipment is 135°C.
Conclusion
ATEX standards ensure that automation control panels and other electrical equipment are designed, constructed, and tested to safely operate in hazardous environments where explosive gases, vapors, or dust may be present. Adhering to ATEX requirements is crucial for ensuring the safety of both equipment and personnel in industries such as oil and gas, chemical processing, mining, and food production. Control panels must meet specific zones and categories based on the level of risk, and they must incorporate appropriate protection methods such as flameproof enclosures, intrinsic safety, and pressurization to minimize the risk of explosion.
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