May. 27, 2024
In hazardous environments where the risk of explosions is a concern, it is crucial to implement safety measures to protect personnel and equipment. A suitable course of action is installing explosion-proof junction boxes as a failsafe for any electrical system that might be exposed to combustible substances in the environment.
However, there are several types of explosion-proof junction boxes available on the market. Each one is rated to withstand various gases and has different Class IDs. To ensure you make the correct choice for your company’s operation, let us explore the different types of explosion-proof junction boxes and discuss their applications and benefits in various hazardous settings.
Learn More: Ultimate Guide to Choosing the Best ex proof Junction Box for Your Business
What is an explosion-proof junction box?
Explosion-proof junction boxes are designed for use in areas with explosive substances or ignition sources. While a standard junction box cannot safeguard against these risks, an explosion-proof junction box will. By isolating specific circuits and preventing wires from coming into contact with combustible elements, the equipment helps prevent the propagation of flames or sparks in an explosive environment, thus safeguarding users operating in hazardous areas.
Types of explosion-proof junction boxes
1. Totally enclosed (TE)
Totally enclosed junction boxes provide a secure enclosure for electrical connections, preventing the entry of potentially explosive substances like gas or vapor. They are also constructed with robust materials that can withstand internal explosions should ignition occur within the equipment. These explosion-proof junction boxes are designed for environments with the potential for sparks or areas with a risk of flammable gases or vapors.
2. Totally enclosed (TE) gas-tight
This type of explosion-proof junction box offers an additional level of protection by ensuring a complete seal against external gases. As such, they can prevent the ingress of any gas, even under high-pressure conditions, making them suitable for environments with high concentrations of hazardous gases.
3. Totally enclosed explosion-proof (TE explosion-proof)
Totally enclosed explosion-proof junction boxes are constructed with flame-arresting materials that help cool down and contain an explosion within the enclosure, preventing flames or sparks from escaping and igniting the surrounding atmosphere. This feature makes them ideal for areas with a potential for explosions.
4. Gas-tight explosion-proof (GE explosion-proof)
Gas-tight explosion-proof junction boxes combine the features of gas-tight and explosion-proof enclosures to prevent the entry of external gases while providing robust protection against internal explosions. As a result, they are suitable for environments where high concentrations of hazardous gases and the risk of explosion are significant concerns.
5. Severe-service explosion-proof (SS explosion-proof)
Ideal for the most challenging industrial environments where resistance to the elements is essential, severe-service explosion-proof junction boxes are specially engineered for extreme operating conditions involving corrosive substances, high temperatures, or mechanical stresses. Naturally, these enclosures are constructed with durable materials to maintain their integrity and withstand harsh environments.
6. Totally enclosed ventilated (TEV)
As the name suggests, totally enclosed ventilated junction boxes are equipped with ventilation systems to allow for the controlled exchange of air within the enclosure. This feature helps dissipate heat generated by the electrical components and prevent the buildup of flammable gases or dust within the equipment. As such, they are ideal for environments where heat dissipation is critical.
Explosion-proof junction boxes are essential in ensuring the safety of personnel and equipment in hazardous environments. By understanding the various types of explosion-proof enclosures available, you can make informed decisions based on the specific needs of your company, thus safeguarding lives and maintaining operational integrity in hazardous environments.
If you are still unsure which explosion-proof junction boxes are most suitable for your needs, do not hesitate to consult our safety specialists. At Supermec, we offer a broad range of explosion-proof enclosures, including Ex d and Ex e junction boxes, at affordable prices. Visit our website today to browse our comprehensive catalogue.
Explosion Proof Enclosures: Safety Standards for ...
Explosion proof enclosures are indispensable to industrial facilities and other organizations that use or store electrical components in hazardous, explosion-prone environments. These sturdy, heavy-duty cabinets are built to minimize the risk of explosion in locations with flammable vapor, gases, and dust, such as oil refineries, chemical plants, fuel servicing sites, feed mills, and plastic/fireworks factories. Their primary purpose is containment in case a protected device explodes within itself.
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Why Use Explosion Proof or Intrinsically Safe Cabinets?
If you’re using electrical components such as knobs and switches in an area that the National Fire Protection Association (NFPA) has designated as hazardous, you need to identify certified explosion proof and intrinsically safe cabinets to store these components. In so doing, you’ll be complying with Occupational Safety and Health Agency (OSHA) guidelines, National Electric Code (NEC) location classifications, as well as specifications set forth by the National Electrical Manufacturers Association (NEMA).
Likewise, Explosion Proof and IS cabinets prevent explosions or infernos from spreading to the surroundings of an internally exploding device. The net outcome is a safer work environment for personnel in industrial facilities that are prone to explosion. The safeguards also help to prevent damage to property, thus shielding investors or manufacturing facilities owners against potentially heavy financial losses.
Explosion Proof Enclosures’ Mechanical Design Aspects
Building an explosion proof junction box or cabinet is pretty much about mechanical engineering design. However, manufacturers may adopt different strategies to build these storage boxes for use in hazardous locations. Here are some common explosion-proofing techniques:
Flame Proofing
Industries that work with high-pressure systems should consider using flame-proof cabinets. With this containment technique, an enclosed device may spark internally or otherwise ignite an explosive mixture within itself, but its proofed enclosure shall limit the impact of any resulting explosion. Sturdy materials, such as cast metal or fabricated steel, are used to build the cabinet’s outer shell. Such a heavy-duty construction contains any excess pressure that an internal eruption creates, preventing propagation into the enclosure’s immediate environment.
Ingress Protection (IP)
Ingress protection involves sealing electrical enclosures to prevent the entrance of foreign bodies, such as vapor and dust.
Pressurization/Purging
Purging is meant to prevent high concentrations of any potentially explosive gas or vapor mixture from accumulating inside an Explosion Proof cabinet with electrical components capable of sparking or heating beyond acceptable temperature limits. This segregation method involves supplying a protective inert gas into the enclosure. Pressurizing, on the other hand, restricts the entrance of potentially combustible dust into the metallic box.
Encapsulation
The encapsulation technique involves filling an explosion proof box with a resin that can resist specific ambient conditions. The material separates electrical components capable of sparking or heating to the point of igniting explosive gases, vapors, or fine particles.
What’s the Distinction Between Explosion Proof and IS Enclosures?
The main difference between an Explosion Proof and IS enclosure is that the former is a containment strategy while the latter is a prevention technique. In other words, intrinsically safe means eliminating the risk of ignition or explosion, rather than containing a problem that has already occurred.
IS design focuses more on the electrical architecture of a component. The objective is to minimize the current, voltage, and temperature of the device’s circuit during operation.
For example, an intrinsically safe junction box is resistant to overheating, and therefore, it’s appropriate for use in industrial facilities prone to high operating temperatures. Its circuitry does not generate sparks or arcs that can detonate an explosive mixture of gas or vapor.
Different Types of Explosion Proof Enclosures/Systems
There are different types of explosion proof enclosures or systems, including:
Junction boxes: These are ideal for rigid conduit systems in potentially-explosive environments like gasoline pumps. They have electrical components and wiring that may spark or short, so they come with rain-tight, heavy-duty Explosion Proof enclosures to internal explosions in check.
Cabinets: Explosion Proof cabinets are used to store hazardous substances, such as flammable liquids and chemicals. They have several fire-safety features, such as sturdy steel enclosures for containing explosions and air vents for maintaining safe interior temperature levels.
Intrinsically safe barriers: These devices control the energy supplied to electrical equipment in hazardous areas. By restricting the supply of energy to circuits, these systems prevent the ignition of combustible substances. For example, isolated barriers protect control circuits from dangerous power surges that may ignite explosive mixtures in their immediate environment.
Various Ratings Applicable to Explosion Proof Enclosure Design
The design and construction of an Explosion Proof or intrinsically safe barrier, junction box, or other containment enclosure must adhere to the standards defined in the NEC hazardous area classifications. However, manufacturers may voluntarily comply with relevant NEMA ratings. The right NEC specifications requirements for you depend on where you intend on deploying your Intrinsically safe or explosion proof cabinet. Here are selected NEMA/NEC classifications and ratings for Explosion Proof / Intrinsically safe enclosures:
NEMA 1
The standard applies to general purpose enclosures for indoor operation. The primary objective of these storage boxes is to prevent housed electrical components from coming into contact with potentially explosive gas, dust, or vapor mixtures.
NEMA 7
These enclosures are for use in locations the NEC designates as Class 1, Group A, B, C, or D. They’re built to contain pressure from an internal explosion of gases. They also limit the impact of any such explosive combustion such that it can’t ignite a flammable gas-air mixture in the immediate surroundings. As such, any enclosed electrical component must not heat external surfaces to temperatures capable of causing a fire or an explosion in the surrounding atmosphere.
NEMA 9
The type 9 standard applies to Explosion Proof enclosures meant for use in NEC locations such as Class 2, Groups E or F. Their objective is to prevent the entrance of dust. Any housed heat-generating component should not cause external surface temperatures to rise to the point of igniting combustible mixtures in the surrounding environment.
International Electro-Technical Code (IEC) Zoning
The IEC designates hazardous areas based on the properties of flammable substances that may be present. It also takes into account the possibility that combustive gases, vapors, or dust may be present. Article 505 of the NEC publication provides similar location classifications. A Zone 1 designation, for example, applies to d-rated flame-proof enclosures for use in environments that are likely to contain combustible amounts of flammable gases during normal operation. It also specifies e-rated cabinets housing electrical components that do not generate arcs, sparks, or extremely high temperatures under normal operating conditions.
Purge/Pressurizing Enclosures
Article 500 of the NEC permits the use of purge or pressurized cabinets as alternative Explosion Proof enclosures under specific conditions. For starters, these storage boxes must satisfactorily address NFPA 496 requirements. IEC Zone 1 and 2 also provide specifications for purged and pressurized storage systems.
Conclusion
Many industrial facilities are storing electrical equipment inside explosion proof enclosures to mitigate different types of hazards, including combustible gases, vapors, and dust, in their operating environment. These organizations are increasingly upgrading their hazardous area certified hardware to intrinsically safe standards to prevent explosions and fire accidents that could harm personnel and damage property. Most importantly, OSHA can heavily penalize companies that don’t use IS/Explosion Proof enclosures appropriate for their dangerous work environment, especially if operating in high-temperature and high-pressure conditions.
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