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For operators of facilities containing hazardous areas, it is very important mechanical and electrical systems used to operate and control facilities are carefully designed and installed in accordance with safety standards set out by government bodies. In order to comply with safety standards, such as the NEC500 or IEC60079, these systems must utilize electronics and electrical products that are specially designed to protect against causing ignition and thus explosions. The general term used to describe these specialized devices and systems is “Explosion Protected”.
There are multiple methods of explosion protection, as defined within the various hazardous area standards. This is necessary as there are many different types of electrical products and systems needed to operate various plants; the technique used to make a high powered multiple KVA UPS system safe is very different to what is utilized to protect a mobile computer….
Below is an overview of the main types of explosion protection manufacturers of hazardous area products utilize:
1. Intrinsically Safe (Ex i)
Description: These systems limit electrical and thermal energy to levels below what can ignite a hazardous atmosphere, even under fault conditions.
Examples:
Process Instrumentation: Zener barriers, galvanic isolators, indicators and displays, temperature, pressure, or level sensors (e.g., 4-20 mA transmitters).
Mobile Devices: Smartphones, tablets, barcode scanners, or wireless transceivers certified for intrinsic safety.
Control Systems: Low-power PLCs or controllers with intrinsically safe I/O modules.
Standards: IEC 60079-11, or UL 913.
Use Case: Ideal for Zone 0 or Zone 1 and Class I Division 1 areas. Allows for live working on instrumentation systems and enables the production of lightweight, ergonomic mobile devices.
2. Explosion-Proof or Flameproof (Ex d)
Description: These systems are housed in robust enclosures that can contain an internal explosion and prevent it from igniting the surrounding atmosphere.
Examples:
Motors and Pumps: Explosion-proof electric motors for pumps or fans.
Wireless Connectivity: Enclose non-hazardous area rated, high-powered wireless access points and RFID readers.
Switchgear and power distribution: Circuit breakers, control panels and UPS systems designed to withstand internal explosions.
Standards: IEC 60079-1 or UL 1203.
Use Case: Common in Zone 1 and Class I Division 1 areas where higher levels of power are required than what is allowed in intrinsically safe systems. Extra care has to be taken with the maintenance of explosion proof systems so that the mechanical protection remains safe and operational.
3. Increased Safety (Ex e)
Description: These systems use design measures (e.g., enhanced insulation, non-sparking components) to reduce the risk of sparks or excessive heat.
Examples:
Terminal Boxes: Junction boxes with increased safety terminals.
Motors: Non-sparking motors with enhanced insulation.
Lighting: Luminaires with high ingress protection (IP) ratings.
Standards: IEC 60079-7, UL 60079-7.
Use Case: Suitable for Zone 1 or 2 (gas) and is a cost- effective, lightweight alternative to explosion proof enclosures when integrated components are suitably rated.
4. Non-Incendive (Ex n)
Description: Designed to prevent ignition under normal operating conditions, though not necessarily under fault conditions. Less stringent than intrinsic safety.
Examples:
Control Panels: Non-incendive control units for monitoring and controlling processes.
Process Instrumentation: Gauges or displays with non-sparking designs.
Standards: ANSI/ISA 12.12.01-2015.
Use Case: Class I Division 2 where hazards are less frequent.
5. Purged and Pressurized (Ex p)
Description: Equipment is housed in an enclosure pressurized with a clean gas (e.g., air or inert gas) to prevent the ingress of hazardous substances.
Examples:
Control Rooms: Pressurized cabinets for control systems or computers.
Analyzers: Gas chromatographs or other analytical instruments.
Motors: Pressurized motors for heavy-duty applications.
Standards: IEC 60079-2, NFPA 496.
Use Case: Common in Zone 1 and Class I Division 1 areas where typically the size of the enclosed solution deems it un-economical or unfeasible to use explosion proof enclosures. Commonly used for control panels including HMI operator interfaces for Division 1 areas.
6. Encapsulated (Ex m)
Description: Components that could cause ignition are encapsulated in a compound (e.g., resin) to prevent contact with the hazardous atmosphere.
Examples:
Transformers: Small encapsulated transformers or coils.
Solenoids: Encapsulated solenoid valves.
Electronics: Sealed circuit boards or modules.
Standards: IEC 60079-18
Use case: One of only two methods allowed for Zone 0 areas. Many intrinsically safe products utilize encapsulation techniques in addition, to protect individual components or circuit boards.
7. Dust-Ignition-Proof (Ex t)
Description: Equipment designed to prevent dust ingress and ignition, typically with high IP-rated enclosures.
Examples:
Motors: Dust-tight motors for grain or coal handling.
Lighting: Dust-protected LED fixtures.
Enclosures: Dust-tight control boxes.
Standards: IEC 60079-31.
Use Case: Sealed enclosures, junction boxes, lighting fixtures and control equipment suitable for installation in Zone 21 and 22 hazardous areas.
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