What is an ATEX coding?
The ATEX code is an alphanumeric string that denotes the certification achieved by the product along with the environment and conditions it is suitable for.
The code can be broken down into a prefix, for example: CE0518 Ex II 2 G and suffix, for example: Ex d IIC T6 Gb.
Products may carry more than one suffix for the same prefix which allows definition of applicability for different environments, for example Gas and Dust hazards.
What does the ATEX prefix mean?
The prefix has 5 sections with the first part confirming that the product complies with the European Directive (CE) and the reference number for the notified body that produced the certification.
After this is the ATEX logo, shown as Ex within a hexagon.
The third section defines the Equipment Group and there are only 2 options for this, I or II where I relates to use in Mines where firedamp may be present and II becoming anywhere other than mines. The vast majority of labels in industrial applications are likely to be Equipment Group II.
The fourth part of the coding is the Equipment Category of which there are 5 variants, M1 & M2 for mine applications and 1, 2 or 3 for anything other than mining. As the number increases in size, the protection level falls such that the highest protection will always be 1 or M1. It is possible for some certifications to state more than one Equipment Category.
The final part of the suffix refers to the Environment which will be G for gases or vapours and D for combustible dusts.
Some devices may be dual certified for both Gas and Dust environments which means there will be a separate suffix for each to define the certification reached.
What does the ATEX suffix mean?
The ATEX suffix gets into the detail of how the device is protected from causing an explosion when installed in a hazardous area and what that hazard conditions are.
The ATEX suffix always starts with Ex to indicate Explosion Protection and is then followed by 4 more sections whether it is for Gas or Dust applications. Many devices may show a separate suffix for Gas and one for Dust because they have achieved testing and certification for both hazards.
Types of protection?
There are many different methods of preventing ignition in a hazardous environment and Types of Protection define which has been used in a particular case. After the initial Ex, will follow either one or two letters to indicate the type of Protection. Some require a second character to stipulate the level of protection and therefore which hazardous area Zone or Category they apply to.
The most common Types of Protection employed with valves and measuring instruments are d (Ex d), e (Ex e), m (Ex m), n (Ex n) and ia (Ex ia).
Types d, e and m are all suitable for Zones 1 or 2, Category 2 or 3 unless they have a second character of a, b, or c which further limits this. Note that types of protection can be combined and de, em or me are all commonly seen.
Ex d is commonly and incorrectly known as explosion proof but it actually is described as flameproof. The housing will contain a flame without allowing it to escape to the hazardous atmosphere.
Ex e means increased safety referring to the lack of arcs, sparks or hot surfaces.
Ex m is encapsulation that prevents the atmosphere reaching any potentially incendive parts.
Ex n is similar to Ex m and means non-sparking which limits it to Zone 2, Category 3 environments.
Ex ia or intrinsically safe is suitable for Zone 0 or 20, Category 1. This achieved through limiting the energy of sparks and surface temperatures through very low power requirements.
Gas or dust?
The next section of the coding refers to the Gas Group or Dust Type of the hazardous environment for which compliance has been certified.
I is solely for mining applications.
II covers all gas hazards and is shown as IIA, IIB or IIC which relates to the potential gases that may be present.
III indicates dust hazards and again is split into IIIA, IIIB and IIIC categories. IIA relates to combustible flyings. IIIB is for non-conductive dusts and IIIC for conductive dusts.
In general, whether it is marked as II or III for the gas group, the C rating is always the safest as it relates to the biggest risk protection.
The Temperature Class rating of T1, T2, T3, T4, T5 or T6 for gases, indicates the classification for the maximum surface temperature for the device and therefore the the distance to the potential ignition temperature for a particular gas.
Dust hazard classifications are shown as T followed by the maximum surface temperature in degrees Celsius.
Equipment protection level?
The Equipment Protection Level is the last part of the coding for Gas or Dust and is similar to the Equipment Category in that Ma and Mb are only related to mining.
Ga, Gb, Gc or Da, Db, Dc are the possible levels with Ga or Da being the highest protection.
Which Zone or Category?
Understanding whether a particular product can be employed in a certain area requires information on how the area and potential risk therein has been classified by the site or plant in question.
The Zones are decided by the site based on a risk assessment of the likelihood of a potentially explosive atmosphere being present.
Zone 0 for gas, 20 for dust or a Category 1 rating means that the risk is continually present and a very high Protection Level is required. In practice for valves and instrumentation, this would usually mean an Ex ia Type of Protection would be the first choice.
Where an explosive atmosphere is not continually present but is likely to occur in normal operation is rated Zone 1, Zone 21 (dust) or Category 2, the common choices for Types of Protection would be versions of Ex d, Ex e,or Ex m.
A place where an explosive atmosphere is not likely to occur in normal operation but could occur for short periods would be classified Zone 2, Zone 22 (dust) or Category 3. Common choices for Tyes of Protection for this environment would be Ex m or Ex n.
Note that regardless of the risk assessment undertaken, it is always possible to use a higher rated Type of Protection that necessary for a particular Zone environment. For example, Ex ia could also be used in Zones 1 and 2 if required.
This nameplate indicates the Notified Body reference for the certification is 0496, the Equipment Group is II (anywhere other than Mines), the Equipment Category is 1 or 2 and the environment is G and Dc where Dc equates to Zone 22 usage.
Ex d indicates flameproof Type of Protection, IIC is the Gas Group, T5 the Temperature Class and Gb the Equipment Protection level.
Ex t indicates a dust tight enclosure, IIIC is the Dust Type, IP67 ingress protection, Temperature Class is 100deg C and Equipment Protection Level Db for Zone 21.
This nameplate indicates the Notified Body reference for the certification is 0575,the Equipment Group is II (anywhere other than Mines), the Equipment Category is 1 (gas only) or 2 and the environment is G and Dc where Dc equates to Zone 22 usage.
Ex d indicates flameproof Type of Protection, IIC is the Gas Group, T6 the Temperature Class and Gb the Equipment Protection level.
Ex t indicates a dust tight enclosure, IIIC is the Dust Type, Temperature Class is 85deg C and Equipment Protection Level Db for Zone 21.
This nameplate carries an ATEX classification based on mechanical risks as it is a pneumatic pressure regulator and there are no electrical parts within it.
It shows that the Equipment Group is II, the Equipment Category is 2 and the Environment is both Gas and Dust.
The Type of Protection is c which means Constructional Safety – any ignition hazards have been eliminated by good engineering practice.
The Gas Group is IIC and Temperature Class is T6 or T5X.
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