Explosion Proof Enclosures: Safety Requirements for ...

Explosion Proof Enclosures: Safety Requirements for Industrial Settings

Industries and businesses using or storing electrical components in hazardous, explosion-prone environments require explosion-proof enclosures. These robust cabinets are essential in areas with flammable vapors, fumes, and dust, such as oil refineries, chemical plants, gasoline service stations, feed mills, and plastic/fireworks industries. Their primary function is to contain any explosion that may occur within the device housed inside.

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Why Opt for Intrinsically Safe or Explosion-Proof Cabinets?

For areas classified as hazardous by the National Fire Protection Association (NFPA), it is essential to use certified explosion-proof and intrinsically safe cabinets to store electrical components like switches and knobs. This ensures compliance with the National Electrical Code (NEC), Occupational Safety and Health Agency (OSHA), and National Electrical Manufacturers Association (NEMA) regulations.

Explosion-proof and intrinsically safe (IS) cabinets prevent explosions from spreading from an internally exploding device to its surroundings. This results in a safer work environment for employees in explosive-prone industrial settings and mitigates property damage, thereby protecting investors and owners from substantial financial losses.

Mechanical Design Aspects of Explosion Proof Enclosures

The mechanical engineering aspects play a crucial role in creating explosion-proof enclosures. Different construction techniques are employed to suit hazardous environments. Here are some common methods:

• Flame Proofing: High-pressure systems benefit from flame-proof cabinets. The enclosure, made from durable materials like cast metal or steel, contains any explosion and prevents it from spreading.
• Ingress Protection (IP): This method seals electrical enclosures to prevent external substances like vapors and dust from entering.
• Pressurization/Purging: Purging fills the enclosure with an inert gas to prevent dangerous gas or vapor concentrations. Pressurization keeps flammable particles out of the metallic box.
• Encapsulation: This involves using a resin to isolate components that could ignite or overheat, thus preventing the ignition of flammable vapors or particles.

Exploring the Difference Between Explosion Proof and IS Enclosures

The key difference between explosion-proof and IS enclosures lies in their approach. Explosion-proof enclosures focus on containment, while IS enclosures emphasize prevention. IS enclosures operate with minimal current, voltage, and temperature to avert ignition or explosion.

An intrinsically safe junction box, for example, is designed to resist overheating and avoid sparks or arcs, making it suitable for high-temperature industrial environments.

Various Types of Explosion Proof Enclosures/Systems

Several types of explosion-proof enclosures and systems exist:

• Junction Boxes: Ideal for gas stations and other locations prone to fire hazards. They feature heavy-duty, rain-tight explosion-proof casings.
• Cabinets: Used for storing hazardous materials like volatile liquids and chemicals. They include safety features like air vents and durable steel casings.
• Intrinsically Safe Barriers: These devices manage energy supply to electrical equipment in hazardous areas, preventing the ignition of combustible materials.

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Design Ratings for Explosion-Proof Enclosures

Explosion-proof and IS enclosures must meet NEC hazardous area classifications. Manufacturers also follow NEMA ratings. The specific NEC requirements depend on the intended application environment.

Conclusion

Storing electrical equipment inside explosion-proof enclosures mitigates risks associated with flammable gases, vapors, and dust. Upgrading to inherently safe hardware is crucial to avoid severe fines from OSHA and ensure the safety of workers and property in high-risk environments.

What Does Explosion Proof Mean?

The term "explosion proof" must be understood in the context defined by the National Fire Protection Association (NFPA) in the National Electric Code (NEC). The NEC outlines protection techniques such as explosion proof, dust ignition proof, dust tight, purged/pressurized, intrinsically safe, and hermetically sealed. These criteria must be met for components used in hazardous locations.

An explosion-proof enclosure is designed to contain any internal explosion and prevent external ignition. However, it is not intended to withstand external explosions.

The NEC also mandates that equipment meet specific temperature requirements relative to the environment where they are installed. Components must be labeled according to their tested and approved classifications.

Rating Protection Techniques

Each protection technique is allowed for specific applications. Explosion-proof components, for instance, are used in Class I, Division 1 or 2 locations.

The NEC specifies that equipment approved for higher classifications can be used in lower classification areas, complying with Division 2 area requirements.

Testing of Explosion Proof Equipment

Nationally recognized testing laboratories, such as Underwriters Laboratories and Intertek, certify products conforming to NFPA and international standards. Approved products bear marks like UL, CSA, and ETL, ensuring compliance with NEC standards.

Prototypes are tested and approved by a testing laboratory, which periodically inspects manufacturers to ensure no design changes.

Engineering Excellence at Specific Systems®

Specific Systems® designs enclosures meeting NEC standards with fully approved components and wiring methods. Features include:

• Hermetically sealed scroll compressors
• Standard totally-enclosed, fan-cooled motors
• Class I Div 1 hazardous duty motors
• UL 508A approved electrical control panels
• CSA C/US approved explosion proof compressors
• Conduit-routed and labeled wiring exceeding NEC standards

For cooler environments, explosion-proof fin tube heaters are required instead of open coil heaters due to explosion hazards.

Specific Systems® explosion-proof crankcase heaters and fin tube heaters meet code requirements and are CSA C/US approved.

Trust Specific Systems®

As a leading manufacturer since 1974, Specific Systems® provides assistance from installation to post-installation for any questions.

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