ATEX

The abbreviation ATEX stands for two European directives. Directive 2014/34/EU addresses manufacturers: it sets the requirements for equipment and protective systems intended for potentially explosive atmospheres. Directive 1999/92/EC addresses operators: it requires explosion risks to be assessed, areas to be classified into zones and the result to be recorded in an explosion protection document. Each country has transposed it into national law – in Germany through the Hazardous Substances Ordinance and the Industrial Safety Ordinance, in Great Britain through DSEAR.

The order is thereby fixed: the operator classifies the zone first, then the equipment is selected for it.

The zone describes how often and for how long a hazardous explosive atmosphere occurs. Zones 0, 1 and 2 apply to gases, vapours and mists, zones 20, 21 and 22 to combustible dusts. Each zone is assigned an equipment category; the letter G or D shows whether the equipment is suitable for gas or dust.

Equipment of a higher category may be used in a less critical zone, but not the other way round.

Zone and category are not enough. The explosion group describes how easily the substance ignites: for gases IIA, IIB and IIC, with IIC – hydrogen and acetylene – the most demanding; for dusts IIIA, IIIB and IIIC. The temperature class limits the maximum surface temperature of the equipment, which must be below the ignition temperature of the substance.

Explosion protection is not purely an electrical matter. Directive 2014/34/EU applies to any equipment with its own potential ignition source – including mechanical and pneumatic equipment. Hot surfaces on bearings and brakes, mechanically generated sparks and electrostatic discharge are among the ignition sources listed in EN 1127-1; for non-electrical equipment the EN ISO 80079-36 and -37 series is relevant.

For handling devices this means: material pairings at friction points, dissipative rollers, hoses and coatings and continuous equipotential bonding are part of the ignition hazard assessment.

A non-electrical device may, for example, carry the marking “II 2G Ex h IIB T4 Gb”. II stands for the equipment group outside mining, 2G for category 2 in gas atmospheres, Ex h for the type of protection of non-electrical equipment, IIB for the explosion group, T4 for the temperature class and Gb for the equipment protection level. Such a device is suitable for zone 1 and zone 2, provided the substances belong to group IIA or IIB and their ignition temperature is above 135 °C.