ATEX Markings

ATEX Markings

ATEX certified products need to use product markings in order to detail what the product is suitable for and what explosive atmospheres it can or cannot be used in.

There are a wide range of markings and categories that need to be communicated through the markings on the products.

What is needed to show a product is ATEX certified?

An ATEX product will need to be checked by notified and authorized bodies, and will also be checked by government. The manufacturer will need a production quality assurance certificate, as well as a EU declaration of conformity, which will (in the UK) be checked and issued by the EECS (Electrical Equipment Certification Service (BASEEFA)) or SCS (Sira certification service).

Some of this information will need to be displayed on the label of the product. The minimum amount of information required on the label, by the ATEX directive, is as follows:

• Name and address of the manufacturer(s) who hold the production quality assurance certificate. Where an item is manufactured in multiple locations or if it is part of an assembly chain, all address must be shown on the label.
• The CE marking - shall be at least 5mm in height wherever possible and shall be followed by the serial number of the notified body certifying the production assurance system or type examination.
• Type or model reference and serial number - (If any)
• Year of manufacture - This may be part of the serial number, to simplify printing and castings.
• The ATEX marking - The "hexagon" symbol, immediately followed by the equipment group or category.
• Additional marking 'as required for safe use' - Such as the explosion classification, ambient temperature limit, supply voltage, etc. - the directive requires this information to be shown but does not define exactly what it is, rather the various product standards (EN and IEC) will each define certain fields and symbols to display.

EEX - This means that the electrical appliance complies with one or several types of protection conforming specifically to the European standards - EN50015 to EN50028.


An example for the labeling that would provide information about the ATEX rating of the solenoid valve and the circumstances it could be used in would look like this:

EEX m II 2GD T4

How this would be interpreted:

EEX - European Explosive atmosphere (Protection concept)

m - The method of protection - m = Encapsulation 

II - Gas groups - This covers all gas groups

2GD - Category 2 Gas and Dust

T4 - Maximum surface temperature = 135°

The following table shows the standards and significant marking/ letter that is assigned to the different types of protection available:

M	Types of protection	EN50018 “d” – Flame proof enclosure
		EN50019 “e” – Increased safety
		EN50020 “i” – Intrinsic safety “ia” “ib”
		EN50028 “m” – Encapsulation
		EN50015 “o” – Oil immersion
		EN50016 “p” – Pressurisation
		EN50017 “q” – Powder filling

Here is a brief summary of each of the types of protection and their methods:

Protection concept	Gas/ Dust	Method of Protection
Flameproof	G	The enclosures can withstand an internal explosion without rupturing, but internal explosions are still possible. The fuel is able to enter the enclosure
Enclosed	D	The enclosure is sealed to prevent ingress of dust, and has a surface temperature below the self-ignition value of the dust. The enclosure is not necessarily gas-tight and so is not suitable for dusts which emit flammable gases on heating.
Pressurised	GD	The enclosure is maintained at higher than atmospheric pressure, using an inert gas. The fuel is not able to enter the enclosure.
Powder-filled	G	The circuitry is fully-immersed in a non-conductive powder. The fuel is able to enter the enclosure.
Oil-filled	G	The circuitry is fully-immersed in a non-conductive oil. The fuel is able to enter the enclosure but does not mix with the oil.
Increased safety	G	Safety measures are used so as to reduce the probability of an internal source of ignition (Spark, hot surface etc.) in normal operation, though they may occur during malfunctions. The fuel is able to enter the enclosure.
Intrinsic safety	GD	During normal operation and specified fault conditions, the circuitry cannot discharge sufficient energy into a spark or thermal event to cause ignition of the fuel. The fuel is able to enter the enclosure.
Encapsulation	GD	The enclosure is filled with a solid resin or polymer. The fuel is not able to enter the enclosure.
Flow restriction	GD	The enclosure is protected by seals, though there is some leakage through the seals as the internal temperature and pressure vary in normal use. The fuel is able to enter the enclosure.
Constructional safety	GD	The mechanical parts of the equipment must be designed so as to prevent any sparks or thermal ignition sources from being created, by selection of materials and operating speeds. Only applies to mechanical equipment with moving parts.
Control of ignition sources	GD	Ignition sources are not present in normal operation, though may occur during malfunctions. Systems are in place to detect any such malfunction and prevent the ignition arising.
Liquid immersion	GD	The equipment is immersed in an inert liquid, isolating any ignition sources and cooling the components (e.g. a gearbox), though the enclosure may not be totally filled. The fuel is able to enter the enclosure.
Inherent safety	GD	The mechanical components have sufficiently low potential energy as to prevent the formation of an ignition source. The fuel is able to enter the enclosure.

Groups of equipment:

I - Electrical apparatus intended for use in mines susceptible to firedamp.

II - Electrical apparatus intended for use in locations with explosive atmospheres other than in mines.

Note:

• For the types of protection "d" and "i", groups II is subdivided into IIA, IIB, IIC.
• For example the "d" and "i" types of protection are respectively subdivided according to the maximum experimental safe gap (MESG) and to the minimum igniting current (MIC).
• The types of protection "d", within class IIB, may be associated with a symbol standing for a specific gas mixture of group IIC, e.g. H₂ (Hydrogen) in this case, the certificate of conformity would be EEx d IIB + H_2.

To better understand what types of protection is being referred to here is a table showing the description and what explosive atmosphere zones the protection symbol is suitable for:

Protection symbol		Zones			Description
		0	1	2
“d”			-	-	Refers to an electrical apparatus whose explosive parts are enclosed in an explosionproof casing. This casing will resist the pressure generated by the internal explosion of an explosive mixture and will prevent the explosion from penetrating to the ambient explosive atmosphere.
“e”			-	-	Refers to an electrical apparatus with a high safety coefficient. Such an apparatus is free from excessively high temperatures and like under normal service conditions, cannot develop inside and outside electric arcs and sparks.
“i”	“ia”	-	-	-	Refers to a circuit in which neither sparks nor temperature can ignite an explosive atmosphere, if generated under the service conditions specified by the standards regulation (normal and faulty operating conditions).
	“ib”		-	-
“m”			-	-	Refers to a special casting in which the parts, of an electrical apparatus which could ignite an explosive atmosphere by either sparking or heating, are encapsulated in a compound in such a way that this explosive atmosphere cannot be ignited.
“o”			-	-	Refers to an electrical apparatus immersed in oil.
“p”			-	-	Pressurisation is maintained against atmosphere by means of a neutral inert gas.
“q”			-	-	Refers to a casting containing powder filling.

The gas groups offer more information on what is required for the zone or area to be safe, because they offer manufacturers a list of gases that will be present. By also displaying the temperature class, the gas groups show what temperatures should not be passed and this gives a clear indicator of the limit that the maximum surface temperature should be. The subdivided groups are referring to as the gas groups. The gas groups show what gases are considered for each subcategory, they give a test gas and a list of other gases that could be present in an area covered by that subcategory and their temperature class.

The gas groups:

Gas groups	Test gas	Common gases and their temperature class
I (mining)	Methane	Methane (aka firedamp)
IIA	Propane	Acetone -T1 Petroleum fuel -T1 Ammonia -T1 Ethane -T1 Methanol -T1 Carbon monoxide -T1 Propane -T1 N-butane -T2 Ethanol -T2 Diesel fuel -T3 Kerosene -T3 Augas fuel -T3 Ethyl nitrate -T6
IIB	Ethylene	Coal gas -T1 Ethylene -T2 Ethyl oxide -T2 Hydrogen sulphide -T3
IIC	Hydrogen	Hydrogen -T1 Acetylene -T2 Carbon disulphide -T6

In order to better understand the information being given here, we also need to look at the temperature classes.
Temperature classes are based on the highest surface temperature reached on the whole or surface of the electrical apparatus operating under the most unfavorable conditions and likely to cause ignition of the explosive atmosphere. 
The temperature classes show what maximum surface temperature can be reached on the surface of the apparatus, giving an idea of what gases that piece of equipment can be used in conjunction with.

The temperature classes:
The temperature classes are displayed in descending order, this means that T6 is safer.

Class	Maximum surface temperature
T1	450°C
T2	300°C
T3	200°C
T4	135°C
T5	100°C
T6	85°C

We will be following this blog up with more information on ATEX and other safety measures that have been implemented and how products need to conform to the standards.

You can view the V-Flow Solutions line of ATEX solenoid valves here:

http://v-flowsolutions.co.uk/solenoid-valves/solenoid-valves/atex-solenoid-valves/

You can read the rest of V-Flows blogs here.

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We will be covering different types of valves in future blog posts.

Other types of valves and products can be found here, on our website:

http://v-flowsolutions.co.uk/

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