The Explosion Protection regulations:
When electronic or electrical equipment of any type is intended for use in a hazardous area, the equipment must be certified as required by the EU directive 94/9/EC. This directive is more commonly known as the ATEX directive (from the French: Atmospheres Explosives). Within Europe certification of products for use in potentially hazardous atmospheres is compulsory. Hazardous areas exist where a potentially explosive mix of air and flammable gasses, or air and dust, or air, dust and gasses may occur.
Outside of the European Union similar regulations apply under the IECEX certification system. In North America products must be listed by UL as suitable for use in hazardous atmospheres. Please note that while the ATEX and IECEX certification system are similar, the North American approach is different; see area classification below.
Certification of products for use in potentially hazardous atmospheres is compulsory.
The directive classifies equipment into groups and categories which are defined by the marking on the equipment – see “Product marking” below.
Classification of Hazardous areas are divided into Zones (European and IECEX method) or Classes and Divisions (North American method) according to the likelihood of a potentially explosive atmosphere being present. European & IECEX classification definition of zone or division, North American classification Zone 0 (gases) An area in which an explosive mixture is continuously present or present for long periods Class I Division 1 (gases) Zone 20 (dusts) Class II Division 1 (dusts) Zone 1 (gases) An area in which an explosive mixture is likely to occur in normal operation Class I Division 1 (gases) Zone 21 (dusts) Class II Division 1 (dusts) Zone 2 (gases) An area in which an explosive mixture is not likely to occur in normal operation and if it occurs it will exist only for a short time Class I Division 2 (gases) Zone 22 (dusts) Class II Division 2 (dusts)
Product marking requires the product to be marked with the CE mark, the ‘EX’ mark and the equipment coding. Heading Mark Use Explosion proof EX (bw) in accordance with the ATEX directive Equipment Group I for use in underground mines II for use in all other places
Category 1 Equipment that is intended for use in areas where an explosive atmosphere is present continuously, for long periods or frequently
Category 2 Equipment that is intended for use in areas where an explosive atmosphere is likely to occur in normal operation and must ensure a high level of protection.
Category 3 Equipment that is intended for use in areas where an explosive atmosphere is unlikely to occur in normal operation and must ensure a normal level of protection.
Gas / Dust G Equipment certified for use in flammable gases. D Equipment certified for use where dust is present in the atmosphere Type of Protection* d Flameproof Ia Intrinsically Safe e Increased safety Gas Group I Mines II Surface above ground industries Gas Sub Group A less easily ignited gases e.g. propane. Group B easily ignited gases e.g. ethylene. Group C most easily ignited e.g. hydrogen or acetylene.
Temperature Classification Hazardous area apparatus is classified according to the maximum surface temperature produced under fault conditions at an ambient temperature of 40°C, or as otherwise specified. The standard classifications are as shown T1 450ºC T2 300ºC T3 200ºC T4 135ºC T5 100ºC T6 85ºC *
There are 8 methods of protection, for simplicity we have listed the one of the most commonly used. Product marking example An ATEX approved electrical product is marked with the following code: EX (bw) II 2G Eexd IIB T4 from the breakdown of the code below it can be seen that the product is flameproof, suitable for use in zone 1 surface applications where gas group B gases may be present and the surface temperature of the product under fault conditions will not exceed 135 ºC. EX (bw) Explosion proof in accordance with ATEX II Equipment group: II surface industries. 2 Category: 2 equipment (suitable for use in Zone 1) G Gas / Dust: Suitable for atmospheres containing gas E European certificate in accordance with harmonised standards Ex Explosion-proof electrical equipment d Type of protection is ‘Flameproof enclosure’ II Gas Group II – surface industries B Gas sub group = B T4 Temperature class T4 Note:
We have included in this section the Metrohm 7A501C which has been used for many years in mines and oil refineries, all over the U.K. It is not ATEX but carries the original BASEFA safety ratings. It is hard to find an intrinsically safe insulation continuity tester, simply because of the requirement to provide the high voltage for insulation testing.
The Leather Case for the Metrohm 74501C is also still available as a spare part. This is required to be in good condition, to keep the intrinsically safe rating, of the 7A501C.
At Glanford Electronics we offer ATEX test instruments and hand held 2-way radios, from manufacturers like:
Fluke, Crowcon, Entel Radio, Tietzsch.
The products include multimeters, Insulation tester, radios, pressure equipment and gas detectors
Please contact us for more information.