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Explosive Atmospheres 101 – Part 1 Why Certification Levels Matter in Explosive Atmospheres

Any industry that processes, uses, or manufactures materials that may give rise to a flammable atmosphere (gas, mist, liquid, dust or even small fibres) may have a potentially explosive atmosphere. Where fuel and oxygen (normally the oxygen in air) are present in the workplace, potential ignition sources must be rendered safe to an acceptable level for the risk. Industries that generate potentially explosive atmospheres classify the dangerous areas based on the likelihood and duration of the explosive atmospheres’ presence. This is referred to as a ‘Zone’ (Europe and NEC505) or ‘Division’ (NEC500).

When a Zone or Division has been established, the manufacturer must take special precautions to reduce the likelihood of an ignition being present to an acceptable level (and possibly to use mitigation measures to lower the consequence of an explosion). These special methods are normally achieved by applying defined ‘levels of protection’ (Referred to as ‘Category’ in ATEX and ‘Equipment Protection Levels’ in IEC). To technically achieve the defined level, we then apply protection concepts (pre-defined design and test methodologies) from published standards. In most cases, there is more than one way to achieve the level of protection; the designer must choose the most suitable to their equipment and manufacturing capability.

Definition of Categories /EPLs

Category 1 Equipment (Zone 0)  Ga, Da          
Must not have ignition sources that can become effective even in a rare malfunction. Equipment in this category is intended for use in areas in which explosive atmospheres caused by mixtures of air and gases, vapours or mists or by air/dust mixtures are present continuously for long periods or frequently.

Category 2 Equipment (Zone 1) Gb, Db          
May have effective ignition sources (with a malfunction applied) protected by a recognised concept. Equipment in this category is intended for use in areas in which explosive atmospheres caused by gases, vapours, mists or air/dust mixtures are likely to occur.

Category 3 Equipment (Zone 2) Gc, Dc           
Must also be protected by a concept when ignition capable (relative to the gas or dust) in normal operation. Equipment in this category is intended for use in areas in which explosive atmospheres caused by gases, vapours, mists or air/dust mixtures are not likely to occur.

The categories in normal practice are equated to the suitability for Zones. Apparatus will be marked with the grouping and category in addition to the marking required by the individual protection.

Given the onerous nature of an explosion, special certification schemes have been set up to control the design and certification of equipment for potentially explosive atmospheres.  Although the schemes differ globally (some are mandatory under law, some are simply procurement specifications), the basis for design and certification is similar, and the schemes normally rely on testing, constructional assessment and production (quality) control by a recognised Certification Body.

The Explosive Atmospheres market is both lucrative and expanding, but the level of certification requirements and checking (both by the buyer and the regulatory authorities) are undoubtedly increasing. To access this market, it is imperative that equipment manufacturers understand the design, manufacture and certification requirements of both discrete apparatus and assemblies to ensure that the products are designed and certified on time and correctly.

ExVeritas provides Product Certification, Management System Certification, Training and Site Safety Services. ExVeritas are an ATEX Notified Body and an IECEx Certification Bod with IECEX Test Laboratories in the UK and USA

www.exveritas.com

 

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