Bürkert demystifies ATEX explosion protection criteria 25 April 2013

Although the ATEX directive has been in force for some years, important criteria that must be considered when selecting an ATEX-certified device are often misunderstood.

So says Bürkert, which says it intends to overcome the problem with its free ATEX poster which can be downloaded from the company's website www.burkert.co.uk

Under the 2003 ATEX directive, manufacturers must design and test equipment to prevent or minimise the risk of explosion in explosive atmospheres.

As part of this process, every electrical or non-electrical source of ignition must be considered, along with the environments and application itself.

The selection criterion for explosion-proof devices breaks down into four main categories.

The first is Zone Classifications. These indicate the type of atmosphere. Zones 0, 1 and 2 relate to combustible gas, fumes or mist. Zones 20, 21 and 22 relate to combustible dust. At the most hazardous end of the scale, zones 0 and 20 are areas in which there is an explosive atmosphere continuously present over long periods, or is frequently present.

By contrast, zones 2 and 22 are areas in which combustible gases are not normally present, or persist only for a short period.

Equipment must provide a certified level of protection and will be classified as suitable for one of these environments.

The second category is: Gas Groups. Gas that is present in the environment should be classed according to explosion groups and temperature classes. The temperature class (T1-T6) gives the ignition temperature of the gas or gas mixture.

The third category is: Temperature Classes and Ambient Temperatures. An approved surface temperature of electrical equipment is given, depending on the temperature class of the gas that will be present. Where the maximum ambient temperature is not defined, a value of 40 degrees C is assumed.

Completing the four categories is: Protection Principle. This is classed as Ex-I input via barrier; or enclosure of the electrical connections via junction box or encapsulation.

Brian Tinham

Related Companies
Burkert Contromatic Ltd

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