Explosion proofing
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Contents
Overview
Potentially Explosive Atmospheres exist where there is a risk of explosion due to mixtures of gas/air, vapour/air, dust/air or other flammable combinations. In such areas there is a necessity to eliminate sources of ignition such as sparks, hot surfaces or static electricity which may ignite these mixtures. Where electrical equipment has to be used in these areas it must be so designed and constructed as to not create sources of ignition capable of igniting these mixtures.
Certification regimes
Directive 2014/34/EU (ATEX)
Electrical equipment used in potentially explosive atmospheres within the European Union must comply with the ATEX Directive. The ATEX Directive lays down “essential requirements” for manufacturers and imposes classification of devices into groups and categories, while distinguishing gas and dust aspects.
The latest ATEX is Directive 2014/34/EU of the European Parliament and of the Council of 26 February 2014 on the harmonisation of the laws of the Member States relating to equipment and protective systems intended for use in potentially explosive atmospheres (recast).
IECEx (International certification system)
IECEx issues an international certificate of conformity for electrical equipment for use in explosive atmospheres. Its aim is to facilitate the international flow of electrical equipment intended to be used in potentially explosive atmospheres (in compliance with one or more international standards defining the type of protective against the risk of explosion) and thus avoiding multiple national certifications and at the same time ensuring an appropriate level of safety. The IECEx certification scheme allows the manufacturers of “Ex-proof” equipment to obtain a Certificate of Conformity that would be accepted in Member States in which this certification scheme is recognized.
UL (America) and CSA (Canada)
The American and Canadian standards are the only ones to have different classifications and locations. ATEX & IECEx work to Groups and Zones whereas the NEC & CEC works to Classes and Divisions, there is no direct comparison between the two. This means that it is imperative that the two standards are not inter-changed within an area.
GOST (Russia & Kazakhstan)
GOST follows similar rules to that of IECEx as far as the breakdown of the zones and other criteria are concerned. However, the requirements for this country mean that separate GOST markings are required on the product. GOST is divided into GOST (R) which is the standard for Russian Federation and GOST (K) that cover Kazakhstan.
Equipment labelling
Equipment for use in potentially explosive areas must display a label indicating the associated safety requirements it conforms with. The label contains a sieres of letters representing different bits of information, including equipment protection level, temperature class, gas group, etc. It will look something like: Ex ib IIB T4 Gb.
The elements of ATEX and IECEx codes are different but are sometimes combined on labels, due to the compatibility of the certification regimes.
