Can DIN rail power supplies be used in hazardous locations?

Yes, DIN rail power supplies can be used in hazardous locations, but only if they are specifically designed and certified for such environments. Hazardous locations refer to areas where there is a risk of explosion or fire due to the presence of flammable gases, vapors, dust, or fibers. In these areas, the electrical equipment, including power supplies, must be intrinsically safe or explosion-proof to prevent ignition of hazardous materials.

Key Considerations for Using DIN Rail Power Supplies in Hazardous Locations:

1. Explosion-Proof and Intrinsically Safe Certifications

The primary consideration when using DIN rail power supplies in hazardous locations is ensuring that the power supply is certified for such environments. Some of the most important certifications include:

1.1. ATEX (ATmosphères EXplosibles) Certification

--- ATEX is the European Union standard for equipment used in explosive atmospheres. If a DIN rail power supply is ATEX-certified, it means the device has been tested and approved for use in areas with explosive gases, vapors, or dust.

--- ATEX Zones: Equipment is rated based on the zones in which it can operate, such as Zone 1 (likely to have explosive atmospheres during normal operation) or Zone 2 (only in the event of a malfunction).

--- Example: A power supply with an ATEX certification would be suitable for use in a petrochemical plant where flammable gases are present.

1.2. IECEx Certification

--- IECEx is an international standard that applies to equipment used in explosive atmospheres. It is similar to ATEX but globally recognized, providing more widespread acceptance in various regions outside Europe.

--- IECEx Zone Classifications: The power supply would be rated for a particular Zone (e.g., Zone 1 or Zone 2 for gases and vapors or Zone 21 or Zone 22 for dusts).

--- Example: A power supply with an IECEx certification could be used in offshore oil rigs or mining operations.

1.3. UL and CSA Certifications (for North America)

--- UL (Underwriters Laboratories) and CSA (Canadian Standards Association) provide certifications for electrical equipment used in hazardous locations in North America.

--- Class I, Division 1 and 2 (Gases and Vapors): For hazardous locations involving gases, where Division 1 covers areas where an explosive gas atmosphere is present during normal operation, and Division 2 covers areas where an explosive gas atmosphere is not likely to occur during normal operations but may be present under abnormal conditions.

--- Class II, Division 1 and 2 (Dust): For hazardous locations involving combustible dust.

--- Example: A power supply with Class I, Division 2 or Class II, Division 1 certification would be suitable for use in chemical plants or grain elevators.

1.4. UL1604 (for hazardous locations in Class I, II, III environments)

--- UL1604 provides ratings for industrial control equipment in hazardous locations, ensuring that the device will not ignite flammable gases, dust, or fibers.

2. Types of Protection Used for Hazardous Locations

DIN rail power supplies suitable for hazardous locations typically incorporate specific types of protection to ensure safety:

2.1. Intrinsic Safety

--- Intrinsic Safety means the power supply is designed to limit the amount of electrical energy released to the environment to a level that is not sufficient to ignite hazardous materials. Intrinsically safe devices are designed with low power levels, limiting the risk of sparks or heat generation.

--- Example: A low-power, intrinsically safe DIN rail power supply might be used in applications like chemical storage facilities, where there is a risk of flammable gas or vapor.

2.2. Flameproof (Explosion-Proof) Enclosures

--- Explosion-proof or flameproof enclosures are designed to contain any internal explosion and prevent it from igniting the external hazardous atmosphere. This is often necessary for equipment that could generate sparks or heat in normal operation.

--- Example: A power supply in a flameproof enclosure might be used in environments with volatile chemicals or oil refineries where an explosion risk is present.

2.3. Encapsulation

--- Encapsulation is a technique where the components of the power supply are encapsulated in a protective material to prevent ignition of surrounding explosive atmospheres. The casing typically contains the equipment, preventing sparks from escaping into the environment.

2.4. Increased Safety

--- Increased Safety involves designing the power supply so that it minimizes the risk of sparks and heat generation. While this is less robust than explosion-proof equipment, it is still suitable for areas where the explosive risk is lower.

--- Example: Suitable for Class 2 Division 2 environments where dust is present but not in hazardous quantities.

3. Factors to Consider When Using DIN Rail Power Supplies in Hazardous Locations

3.1. Power Rating

--- In hazardous locations, the power rating of the DIN rail power supply should match the load requirements, but it should also be designed to operate safely within the constraints of the environment.

--- Example: In an area with high ambient temperatures, a power supply with a higher temperature tolerance and lower heat generation might be necessary.

3.2. Ambient Temperature Range

--- Hazardous locations can often have extreme environmental conditions, including high temperatures, moisture, and corrosive substances. Choosing a power supply with a suitable temperature range (e.g., -20°C to +60°C or more) is essential for ensuring reliable operation.

3.3. Proper Installation and Maintenance

--- Even with certification, proper installation and regular maintenance are essential to ensure the safety of the system. For example, proper grounding, cabling, and connection to the DIN rail are critical for minimizing risks of electrical faults.

--- Inspection and Maintenance: Hazardous location power supplies should be regularly inspected for signs of wear, corrosion, or other damage that might compromise their safety.

3.4. Availability of Suitable Enclosures

--- In some hazardous environments, DIN rail power supplies are housed within enclosures that are certified for the environment, such as flameproof or explosion-proof enclosures. These enclosures prevent external hazardous elements from affecting the power supply and vice versa.

4. Applications in Hazardous Locations

DIN rail power supplies designed for hazardous locations are used in various industries, including:

--- Oil and Gas: In offshore platforms, refineries, and drilling sites, where gas leaks, flammable vapors, or dust might be present.

--- Chemical Processing: In chemical plants and storage facilities, where explosive gases or dust can be present due to chemical reactions or processing.

--- Mining: In underground mines or areas where there is the risk of combustible dust and gases.

--- Pharmaceutical and Food Production: Where volatile chemicals or dust from powdered materials can create hazardous environments.

--- Automotive: In environments where hazardous vapors or gases are used in manufacturing processes.

--- Wastewater Treatment: In wastewater treatment plants where methane or other gases can be present.

5. Conclusion

DIN rail power supplies can be used in hazardous locations, but only if they meet the required certifications and protection standards, such as ATEX, IECEx, or UL for hazardous environments. These power supplies are designed with enhanced safety features like intrinsic safety, explosion-proof enclosures, and increased safety to prevent any risk of ignition in explosive atmospheres. Choosing the right power supply involves considering the specific zone classification, ambient temperature, power rating, and protection features needed for safe and reliable operation in hazardous locations.