Why Atex?

Previous Hazardous Standards were based on standards and laws of each EU member State. This led to various different acceptable standards in each country.

The introduction of EN50014 (IEC 60079) the first “European Standard” unfortunately translated by each country to suit their own interpretation. Atex was the next step in the process as it is a European Standard that is not open to interpretation.

ATEX is the term used for the European Unions directive 94/9/EC that concerns equipment and protective systems intended for the use in potentially explosive atmospheres. The purpose of the directive is to facilitate trade within the EU buy aligning the laws of the member states regarding the safety requirements for hazardous area products.

The Directive does not cover:

1. Medical devices intended for use in a medical environment
2. Equipment and protective systems where the explosion hazard results exclusively from the presence of explosive substances or unstable chemical substances
3. Equipment intended for use in domestic and non-commercial environments where potentially explosive atmospheres may only rarely be created, solely as a result of the accidental leakage of fuel gas.
4. Personal protective equipment covered by Directive 89/686/EEC
5. Seagoing vessels and mobile offshore units together with equipment on board such vessels or units Means of transport, i.e. vehicles and their trailers intended solely for transporting passengers by air, road, rail or water networks, as well as means of transport in so far as such means are designed for transporting goods by air, by public road or rail networks or by water.
6. Vehicles intended for use in a potentially explosive atmosphere shall not be excluded.

Symbols

	Under the Old Directive, the "Epsilion x" (shown) symbol indicated conformity with CENELEC requirements. This symbol was allowed to be applied to products which were considered to be final assemblies, NOT empty enclosures or component parts such as terminal blocks, operators, breather drains, etc..
	Under the New Directive, the "Epsilion x" symbol will move into the marking string and be used to indicate explosion protection. The "CE" mark will now indicate conformity to the ATEX Directive. This mark can only be applied to final assemblies and not to empty enclosures or component parts.

Explosion Protection

There are many ways of protecting Plants from risk of explosion due to hazardous Gasses and Dusts.

The Explosion Triangle shows we need three component parts to create an explosion:

1. Oxidiser (Oxygen / Air)
2. Fuel (Gas / Dust)
3. Energy (Ignition Source)

Remove any one and the area is safer.

Air

This is naturally occuring all around us and would be very difficult to remove.

Gas / Dust

This has to be the right mixture before an explosion will occur. Too much air or too much gas / Dust and the mixture will not ignite.
If the explosive atmosphere is caused by gases, vapours and mists the hazardous area is coded G. If the explosive atmosphere is caused by dusts the hazardous area is coded D.

Ignition Source

This can be in the form of a Naked Flame, A Hot Surface, Mechanically Generated Sparks, Electrically Generated Sparks, or Electrostatic Discharge etc..

The ATEX standards call for the manufacturers of hazardous area electrical equipment to label their products with the following information.

1. Name of manufacturer
2. Product type code
3. Address of manufacturer
4. Year of manufacture
5. Marking in accordance with directive 94/9/EC II 3 GD – group II location, category 3 equipment, for gas and dust hazards
6. Marking in accordance with European standards EEx nR II T – built and tested to European standards, type of protection, explosion group, temperature class
7. CE marking together with notified body registration number
8. Notified testing body and reference number
9. Serial number
10. Technical data
11. Ingress protection

Explosion Groups

Explosion protected electrical equipment is classified in terms of the ignition temperature, the ignition capability and flame transmission capacity of the explosive atmosphere in which it is designed to operate.

In the first instance equipment is divided into two groups depending on its location above or below ground.

Group I Electrical equipment for use below ground in areas susceptible to firedamp.
Group II Electrical equipment for all other areas.
Group II equipment is further divided into three sub groups depending on the ignition and flame transmission characteristics of the explosive hazard.

These sub-groups are designated IIA, IIB and IIC.

Zones the probability of an explosive atmosphere occurring

Zone 0 defines an area in which an explosive atmosphere caused by a mixture of air and gases, vapours and mists is present continuously for long periods or very frequently (Category 1G under Atex)

Zone 1 defines areas in which an explosive atmosphere caused by a mixture air and gases, vapours and mists is expected to occur occasionally. (Category 2G under Atex)

Zone 2 defines areas in which an explosive atmosphere caused by a mixture of air and gases, vapours and mists is unlikely and if it should occur it will be for a short time and then only rarely. (Category 3G under Atex)

Zone 20 defines an area in which an explosive atmosphere caused by a cloud of combustible dust and air is present continuously for long periods or very frequently. (Category 1D under Atex)

Zone 21 defines areas in which an explosive atmosphere caused by a cloud of combustible dust and air is expected to occur occasionally. (Category 2D under Atex)

Zone 22 defines areas in which an explosive atmosphere caused by a cloud of combustible dust and air is unlikely and if it should occur it will be for a short time and then only rarely. (Category 3D under Atex)

The main differences within ATEX are that Zones 0, 1 & 2 have now been replaced with Categories 1, 2 & 3, the inclusion of Dusts into Zones, and accounting for Mechanical items in Hazardous areas.

Types of Electrical Equipment Suitable for use in Potentially Explosive Atmospheres
Different techniques are used to prevent electrical equipment from igniting explosive atmospheres. There are restrictions on where these different types of equipment can be used as follows:

Ingress Protection

Two digits are used to denote the level of ingress protection that a piece of apparatus enjoys :–
(The first digit denotes the level of protection against solid objects and the second against liquids)

Note: IP54 is the minimum protection allowed for Hazardous Area Equipment
North American practice is to use NEMA standards to describe ingress protection, i.e:

NEMA 3 is similar to IP 54
NEMA 4 is similar to IP 55
NEMA 4x is similar to IP 56
NEMA 6 is similar to IP 67

World-wide Certification

Most countries outside Europe or North America use the IEC Standards as a basis for their own national standards. The Russian Federation Certifies Equipment to GOST Standards, these closely follow CENELEC practice.

Future Certification

There is a scheme in place which when fully adopted will allow for internationally recognised certification to become a reality, the IEC EX SCHEME. This uses the IEC standards and IEC recognised test and certification bodies to issue mutually recognised test reports and certificates. The scheme is in its infancy and its level of success cannot yet be measured.