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    Electrical and mechanical equipment for use in explosive atmospheres

    Summary

    The new ATEX directive (2014/34/EU) will come into force on the 20th April 2016 and will immediately replace the current one 94/9/ECwithout a transition period.

    The ATEX Directives applies to equipment intended to be used where an explosive atmosphere is present, when they are first placed on the Union Market

    An explosive atmosphere is a mixture of flammable substances (gases, vapours, mists or dusts) with air, under atmospheric conditions; once an explosive atmosphere is ignited the combustion spreads to the entire unbranded mixture.

    Products that comply with the ATEX Directive bear the Ce and the ATEX marking.

    The ATEX directive defines procedures that manufacturers have to apply before placing a product on the market; these procedures are different according to the likelihood of the product to be surrounded by an explosive atmosphere ( that is, according to their category). The procedures are intended to demonstrate the due diligence of the manufacturers of the equipment and, in some cases, involves Notified Bodies.

    The ATEX directive is strictly linked to the protection of workers from the risks associated with an explosion; in cad a work place contains an explosive atmosphere ( although its presence might be rare) employers' obligations are described in the DSEAR Regulations (implementing the Directive 99/92/EC).

     

    Scope

    This Directive applies to electrical and mechanical equipment intended to operate within an explosive atmosphere and falling into these definitions:

    equipment

    protective systems

    components (items essential to the safe functioning of equipment and protective systems but with no autonomous function)

    The Directive also applies to devices intended for use outside potentially explosive atmospheres but required for or contributing to the safe functioning:

    safety devices

    controlling devices

    regulating devices

     

    Equipment Classification


    The directive does not use Zone numbers in the classification of hazardous areas, preferring to refer to their definitions (e.g. 'An area where an explosive atmosphere occurs frequently or continuously' for Zone 0) but it is useful to understand the classification system commonly used to describe areas where explosive atmospheres may occur. Usually, a series of zones based on the likelihood of presence of an explosive atmosphere are defined (the following are based on BS EN 60079-10: 2003): 

    Zone for gases, vapour and mists

    Zone for combustible dusts

    Conditions

    0

    20

    Explosive atmosphere will be present continuously

    1

    21

    Explosive atmosphere will be present some of the time (e.g. due to operational reasons)

    2

    22

    Explosive atmosphere may be present (e.g. in the event of a fault)


    Equipment is selected on the basis of its suitability for use in these conditions. There is a sub-division, which separates equipment for use in mines from all other equipment. The full list of categories is as follows: 

    Group

    Equipment Category

    Locations

    Corresponds to

    Comments

    Gases

    Dusts

    I

    M1

    Mines

    n/a

    capable of functioning safely in the presence of an explosive atmosphere

    I

    M2

    Mines

    n/a

    must be de-energised when an explosive atmosphere is present

    II

    1G

    1D

    Other

    Zone 0

    protection assured in the event of two independent failures

    II

    2G

    2D

    Other

    Zone 1

    protection assured in the event of foreseeable failures

    II

    3G

    3D

    Other

    Zone 2

    protection assured during normal operation

     

    Requirements
    The ATEX Directive 94/9/EC describes what a manufacturer has to do before placing the product on the market intended to operate into an explosive atmosphere. Some requisites are common to any equipment (e.g. the obligation to put the CE marking and the ATEX logo on the equipment; the obligation to provide a Declaration/Attestation of Conformity to the final user, the obligation to produce a Technical File, etc.). for Pete: do you find that including the word “Attestation” leads to complications and misleading? Other requisites are different, according to the classification of the equipment: the Directive sets different Essential Health And Safety Requirements EHSR and different levels of involvement of Notified Bodies.

    A Notified Body is an organization having the authority to verify if a product meets its mandatory requirements by the mean of inspection, test and surveillance.