Explosion Proof Enclosures: Safety Requirements for ...

Industrial facilities and other businesses that use or store electrical components in risky, explosion-prone settings need explosion safe enclosures. In areas with flammable vapour, fumes, and dust, such as oil refineries, chemical plants, gasoline servicing sites, feed mills, and plastic/fireworks industries, these strong, heavy-duty cabinets are designed to reduce the risk of explosion. Their main function is containment in the event that a protected device detonates inside of itself.

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Why Use Intrinsically Safe or Explosion-Proof Cabinets?

You must find certified explosion proof and intrinsically safe cabinets to store electrical components like knobs and switches if you use them in an area that the National Fire Protection Association (NFPA) has classified as hazardous. By doing this, you'll be adhering to National Electrical Code (NEC) location classifications, Occupational Safety and Health Agency (OSHA), and National Electrical Manufacturers Association (NEMA) regulations (NEMA).

Similarly, Explosion Proof and IS cabinets stop explosions or infernos from spreading from an internally exploding gadget to its surrounds. The end result is a safer working environment for employees in explosive-prone industrial plants. In addition to preventing property damage, the measures protect investors or the owners of production plants from potentially significant financial losses.

Explosion Proof Enclosures’ Mechanical Design Aspects

Mechanical engineering design is essentially what goes into creating an explosion-proof junction box or cabinet. However, manufacturers may employ various construction techniques to create these storage boxes for use in dangerous environments. Here are some typical methods for preventing explosions:

Flame Proofing

Businesses that use high-pressure systems want to think about employing flame-proof cabinets. An enclosed device may spark internally or otherwise ignite an explosive combination within itself using this containment technique, but the proofed enclosure will mitigate the effects of any ensuing explosion. The cabinet's outside shell is constructed from sturdy materials like cast metal or manufactured steel. Any extra pressure that an internal eruption generates is contained by the enclosure's robust design, preventing spread to the immediate surroundings.

Ingress Protection (IP)

Sealing electrical enclosures with ingress protection entails preventing the entry of external substances like vapour and dust.

Pressurization/Purging

Purging is used to keep dangerously high concentrations of any gas or vapour mixture from building up inside an explosion-proof cabinet that has electrical components that could spark or get too hot. This segregation technique includes filling the cage with a protective inert gas. On the other side, pressurising prevents flammable particles from entering the metallic box.

Encapsulation

The encapsulation method entails adding a resin that can withstand particular environmental conditions to an explosion-proof box. The substance keeps electrical components apart that have the potential to ignite or heat up to the point of igniting flammable vapours, fumes, or tiny particles.

What’s the Distinction Between Explosion Proof and IS Enclosures?

Explosion Proof and IS enclosures vary primarily in that the former is a containment strategy and the latter is a prevention method. In other words, intrinsic safety refers to preventing the possibility of an igniting or explosion rather than only limiting an existing issue.

IS design places more emphasis on a component's electrical architecture. The goal is to operate the device with as little current, voltage, and temperature as possible.

For instance, an intrinsically safe junction box resists overheating, making it suitable for use in industrial facilities that frequently experience high operating temperatures. Its circuitry doesn't produce sparks or arcs that could set off an explosive gas or vapour mixture.

Different Types of Explosion Proof Enclosures/Systems

There are various explosion-proof enclosures and systems, such as:

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Explosion Proof Lighting

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Junction boxes: These are perfect for use with rigid conduit systems in locations like gas stations that could catch fire. They have wiring and electrical parts that could spark or short, so they have heavy-duty, rain-tight explosion-proof casings to prevent interior explosions.

Cabinets: Hazardous materials, including volatile liquids and chemicals, are kept in explosion-proof cabinets. They have a number of safety features, including air vents to maintain safe inside temperatures and strong steel casings to contain explosions.

Intrinsically safe barriers: These gadgets regulate the energy delivered to electrical equipment in risky environments. These systems avoid the combustion of combustible materials by limiting the energy supply to circuits. Isolated barriers, for instance, shield control circuits from hazardous power surges that could set off explosive mixes in the vicinity.

Different Ratings for Explosion-Proof Enclosure Design

Explosion-proof or intrinsically safe barriers, junction boxes, and other containment enclosures must be designed and built in accordance with the guidelines outlined in the NEC hazardous area classifications. Manufacturers may, however, voluntarily adhere to pertinent NEMA ratings. Where you plan to use your intrinsically safe or explosion-proof cabinet will determine the appropriate NEC criteria for you.

Conclusion

To reduce various forms of risks, such as flammable gases, vapours, and dust in their operational environment, many industrial facilities store electrical equipment inside explosion-proof enclosures. In order to avoid explosion and fire mishaps that could endanger workers and cause property damage, these firms are increasingly upgrading their hazardous area certified hardware to intrinsically safe requirements. In particular, if operating in high-temperature and high-pressure environments, OSHA can severely fine businesses that don't have IS/Explosion Proof enclosures adequate for their hazardous work environment.

What does explosion proof mean?

To understand what is meant by explosion proof, we must look at the context of the term and the organization that defined it. The National Fire Protection Association (NFPA) began publishing the National Electric Code (NEC®) in 1897. The NEC® is also known as NFPA 70 and ANSI/NFPA 70 from its inclusion in the body of NFPA codes.

The NEC® includes definitions for several types of protection techniques acceptable when designing products for use in hazardous (classified) locations: Explosion proof, dust ignition proof, dust tight, purged/pressurized, intrinsically safe, and hermetically sealed. These definitions set the criteria that must be met by all components installed in hazardous (classified) locations.

To meet the criteria for the explosion proof rating, an enclosure must be able to contain any explosion originating within its housing and prevent sparks from within its housing from igniting vapors, gases, dust, or fibers in the air surrounding it. Therefore, explosion proof, when referring to electrical enclosures, does not mean that it is able to withstand an exterior explosion. Instead, it is the enclosures ability to prevent an internal spark or explosion from causing a much larger blast.

Additionally, the NEC states that equipment must meet the temperature requirements of the specific application in which it is to be installed. This means that the operating temperature of the motor (and its enclosure) or other component cannot be greater than the lowest ignition/combustion temperature of the gases or dusts in the atmosphere where the component is to be installed.

All components are labeled on their nameplate with the distinct classification in which they have been tested and approved for installation.

How are the protection techniques rated?

Each of the protection techniques mentioned above is permitted for use only in very specific applications. For example, components and equipment complying to the dust tight specification are approved for use in Class II, Division 2, or Class III, Division 1 or 2 locations, while those listed as explosion proof are approved for use in Class I, Division 1 or 2 locations.

Often, those products listed for a higher classification surpass the requirements for lower classifications. In fact, the NEC® explicitly states “Equipment that has been identified for a Division 1 location shall be permitted in a Division 2 location of the same class, group, and temperature class,” thereby complying with requirements for the Division 2 areas [ANSI/NFPA 70:500.8(A)(2)].

Who tests Explosion Proof equipment?

Nationally recognized testing laboratories such as Underwriters Laboratories and Intertek use marks to denote that the products they have tested conform to the standards set by the (NFPA) and by other international standards organizations. These marks, which include UL, CSA, ETL, and others, can be looked for to determine compliance with the standards. Products that do not bear these marks may not meet the requirements of the NEC.

A ready for production prototype is sent to a testing laboratory. Once approved, that laboratory sends inspectors to the manufacturer on occasion to ensure that nothing has been changed in the design or manufacturing of the component.

Specific Systems® are engineered to perform

Unlike systems sold by HVAC modifiers, units fabricated by Specific Systems® are engineered from the sheet metal to the compressor choices to meet the standards laid out in the NEC®. Specific Systems® uses only fully approved and labeled components and wiring methods on all systems.

• Hermetically sealed scroll compressors in every unit
• Standard totally-enclosed, fan-cooled (TEFC) motors
• Class I Div 1 hazardous duty motors, when specified
• Electrical control panels built in our UL 508A approved electrical shop
• CSA C/US approved explosion proof compressors
• UL Listing and CSA C/US Approval of all InPac® and AirPak units
• All wiring is properly routed through conduit and labeled in order to exceed NEC® standards

Some refineries and processing facilities operate in cooler environments. Because of the often cooler ambient temperatures, heat is often required in these applications. However, typical open coil heaters can not be used in hazardous areas due to the explosion hazard. For these applications, explosion proof fin tube heaters must be utilized.

Explosion proof heaters incorporate fin tube heating elements and enclosed electrical connections to meet code and reduce surface temperatures. Specific Systems® explosion proof heaters are CSA C/US approved.

Additionally, explosion proof crankcase heaters are used in these conditions instead of standard crankcase heaters.

Depend on Specific Systems®

Specific Systems® has been building HVAC and pressurization units for hazardous (classified) areas since 1974, and is the oldest and largest manufacturer in the industry. Because we build the units, we will be here to assist with any questions you have post-installation.

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