ATEX directive

The ATEX directives consists of two EU directives describing the minimum safety requirements of the workplace and equipment used in explosive atmosphere. ATEX derives its name from "Appareils destinés à être utilisés en ATmosphères EXplosives" (french).

Not to be confused with CE marking.

Directives
Mark for ATEX certified electrical equipment for explosive atmospheres.

Organisations in the EU must follow Directives to protect employees from explosion risk in areas with an explosive atmosphere.

There are two ATEX Directives (one for the manufacturer and one for the user of the equipment):

  • the ATEX 214 "equipment" Directive 2014/34/EU - Equipment and protective systems intended for use in potentially explosive atmospheres
  • the ATEX 137 "workplace" Directive 1999/92/EC - Minimum requirements for improving the safety and health protection of workers potentially at risk from explosive atmospheres.

Note: The ATEX 95 "equipment" Directive 94/9/EC, was withdrawn on 20 April 2016 when it was replaced by ATEX 214 Directive 2014/34/EU. ATEX Directive 2014/34/EU is mandatory for manufacturers as of 20 April 2016 as stated in article 44 of the Directive.

ATEX Directive 2014/34/EU was published on 29 March 2014, by the European Parliament. It refers to the harmonisation of the laws of the Member States relating to equipment and protective systems intended for use in potentially explosive atmospheres.

Regarding ATEX 99/92/EC Directive, the requirement is that Employers must classify areas where potentially explosive atmospheres may occur, into zones. The classification given to a particular zone, and its size and location, depends on the likelihood of an explosive atmosphere occurring and its persistence if it does.

Equipment in use before July 2003 is allowed to be used indefinitely provided a risk assessment shows it is safe to do so.

The aim of Directive 2014/34/EU is to allow the free trade of ‘ATEX’ equipment and protective systems within the EU by removing the need for separate testing and documentation for each member state.

The regulations apply to all equipment intended for use in explosive atmospheres, whether electrical or mechanical, including protective systems. There are two categories of equipment 'I' for mining and 'II' for surface industries. Manufacturers who apply its provisions and affix the CE marking and the Ex marking are able to sell their equipment anywhere within the European Union without any further requirements with respect to the risks covered being applied. The directive covers a large range of equipment, potentially including equipment used on fixed offshore platforms, in petrochemical plants, mines, flour mills and other areas where a potentially explosive atmosphere may be present.

In very broad terms, there are three preconditions for the directive to apply: the equipment a) must have its own effective source of ignition; b) be intended for use in a potentially explosive atmosphere (air mixtures); and c) be under normal atmospheric conditions.

The directive also covers components essential for the safe use and safety devices directly contributing to the safe use of the equipment in scope. These latter devices may be outside the potentially explosive environment.

Manufacturers/suppliers (or importers, if the manufacturers are outside the EU) must ensure that their products meet essential health and safety requirements and undergo appropriate conformity procedures. This usually involves testing and certification by a ‘third-party’ certification body (known as a Notified Body e.g. Vinçotte, Intertek, Sira, Baseefa, Lloyd's, TUV ICQC) but manufacturers/suppliers can ‘self-certify’ Category 3 equipment (technical dossier including drawings, hazard analysis and users manual in the local language) and Category 2 non-electrical equipment, but for Category 2 the technical dossier must be lodged with a notified body. Once certified, the equipment is marked by the ‘CE’ (meaning it complies with ATEX and all other relevant directives) and ‘Ex’ symbol to identify it as approved under the ATEX directive. The technical dossier must be kept for a period of 10 years.

Certification ensures that the equipment or protective system is fit for its intended purpose and that adequate information is supplied with it to ensure that it can be used safely. There are four ATEX classification to ensure that a specific piece of equipment or protective system is appropriate and can be safely used in a particular application: 1. Industrial or Mining Application; 2. Equipment Category; 3. Atmosphere; and 4. Temperature.

The ATEX as an EU directive finds its US equivalent under the HAZLOC standard. This standard given by the Occupational Safety and Health Administration defines and classifies hazardous locations such as explosive atmospheres.

Technical definitions

In DSEAR, an explosive atmosphere is defined as a mixture of dangerous substances with air, under atmospheric conditions, in the form of gases, vapours, dusts or fibres in which, after ignition has occurred, combustion spreads to the entire mixture.

Atmospheric conditions are commonly referred to as ambient temperatures and pressures. That is to say temperatures of −20 °C to 40 °C and pressures of 0.8 to 1.1 bar.[1]

Zone classification

The ATEX Directive covers explosions from flammable gas/vapours and combustible dust/fibres (which, contrary to common perception, can lead to hazardous explosions[2])

Hazard – Gas/vapour/mist

  • Zone 0 – A place in which an explosive atmosphere consisting of a mixture with air of dangerous substances in the form of gas, vapour or mist is present continuously or for long periods or frequently.
  • Zone 1 – A place in which an explosive atmosphere consisting of a mixture with air of dangerous substances in the form of gas, vapour or mist is likely to occur in normal operation occasionally.
  • Zone 2 – A place in which an explosive atmosphere consisting of a mixture with air of dangerous substances in the form of gas, vapour or mist is not likely to occur in normal operation but, if it does occur, will persist for a short period only.

Hazard – dust/fibres

  • Zone 20 – A place in which an explosive atmosphere in the form of a cloud of combustible dust in air is present continuously, or for long periods or frequently.
  • Zone 21 – A place in which an explosive atmosphere in the form of a cloud of combustible dust in air is likely to occur in normal operation occasionally.
  • Zone 22 – A place in which an explosive atmosphere in the form of a cloud of combustible dust in air is not likely to occur in normal operation but, if it does occur, will persist for a short period only.
Effective ignition source

Effective ignition source is a term defined in the European ATEX directive as an event which, in combination with sufficient oxygen and fuel (gas, vapour, dust or fibres), can cause an explosion. Methane, hydrogen or coal dust are examples of possible fuels.[3]

Effective ignition sources are:

  • Lightning strikes.
  • Open flames. This varies from a lit cigarette to welding activity.
  • Mechanically generated impact sparks. For example, a hammer blow on a rusty steel surface compared to a hammer blow on a flint stone. The speed and impact angle (between surface and hammer) are important; a 90 degree blow on a surface is relatively harmless.
  • Mechanically generated friction sparks. The combination of materials and speed determine the effectiveness of the ignition source. For example, 4.5 m/s steel-steel friction with a force greater than 2 kN is an effective ignition source. The combination of aluminium and rust is also notoriously dangerous. More than one red hot spark is often necessary in order to have an effective ignition source.
  • Electric sparks. For example, a bad electrical connection or a faulty pressure transmitter. The electric energy content of the spark determines the effectiveness of the ignition source.
  • High surface temperature. This can be the result of milling, grinding, rubbing, mechanical friction in a stuffing box or bearing, or a hot liquid pumped into a vessel. For example, the tip of a lathe cutting tool can easily be 600 Celsius (1100 °F); a high pressure steam pipe may be above the auto-ignition temperature of some fuel/air mixtures.
  • Electrostatic discharge. Static electricity can be generated by air sliding over a wing, or a non-conductive liquid flowing through a filter screen.
  • Radiation.
  • Adiabatic compression. Air is pumped into a vessel and the vessel surface heats up.

See also

References
  1. "ATEX and explosive atmospheres". HSE UK.
  2. https://www.powderprocess.net/Safety_ATEX.html
  3. Michelis, J.: "Explosionsschutz im Bergbau unter Tage", Verlag Glückauf Essen, 1998, ISBN 3-7739-0900-4

Atmospheres Regulations 2016] (UK)

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