Technical Development of Explosion Protection
In the 19th century, electrical equipment was introduced into industry and households. Immediately afterwards, the occurrence of methane and coal dust in hard coal mining prompted the development of the basics of electrical explosion protection. The advantages of electricity were so convincing that intensive work was carried out to find a way to reliably prevent contact between an explosive atmosphere and ignition sources - originating from the use of electrical equipment - and thus prevent explosions.
These days, the construction of explosion protected equipment goes far beyond the field of electrical engineering. As will be demonstrated in the further descriptions, in future non-electrical equipment will also require testing or at least assessment. Here the knowledge gained by manufacturers over the decades on the explosion protection of electrical equipment is particularly important and it now also benefits the manufacturers of non-electrical equipment. These manufacturers often buy electrical equipment, which automatically creates a contact.
Internationally harmonized design regulations for electrical engineering have been drawn up in the form of IEC standards and reports have been formulated, largely in conformance to the CENELEC standards. The numerical sequences used in IEC, CENELEC and DIN are currently being standardised. This reorganisation involves a lot of ongoing changes at present but it will make work easier in the future.
In the Directive 94/9/EC the European Community has provided itself with obligatory, uniform design requirements for the explosion protection of systems, devices and components and this directive is supported by the EN standards referred to in the above and the CENELEC and CEN standardisation organisation.
Explosion and basis for an explosion
An explosion is defined as a sudden reaction involving a rapid physical or chemical oxidation reaction or decay generating an increase in temperature or pressure or both simultaneously. The most familiar reactions are those of flammable gases, vapours or dusts with the oxygen contained in the air.
As a rule, for explosions to happen in atmospheric air, three factors have to be present at the same time:
- flammable substance
- oxygen (air)
- source of ignition
Prevention of explosions
Explosion protected equipment is able to exclude one of the preconditions for an explosion - the ignition source - and is in that way an important contribution to explosion protection. In domestic areas, constructional measures ensure that normally an explosive atmosphere cannot form. The conscious restriction of these measures, e. g. the intended, unimpeded flow of flammable gases or a reduction in ventilation can lead to explosions if an ignition source is also present.
The easiest and simplest way to understand small and safe explosions is by looking at a gas lighter. When the nozzle of the lighter is opened, it releases a small amount of flammable gas. This gas mixes with the surrounding air, the spark from the flint ignites the mixture, and a weak sound is heard - the burning. Some distance away from the nozzle the proportion of the flammable gas is already so low that the explosion and the flame are restricted to the immediate vicinity of the nozzle. In other words, the design of the gas lighter has ensured that it is safe to use.
The effect of an explosion in enclosed spaces and under non-atmospheric conditions - e. g. under increased pressure - is often more powerful. Just think of the useful application of explosions in vehicle engines.
To attain effective explosion protection against non-controlled, unintended explosions linked to disastrous consequences, it is necessary to remove one of the three factors.
BARTEC products prevent ignition sources or coming together of such sources with potentially explosive atmospheres. They effectively prevent explosions because the other two factors - the oxygen in the air and often the flammable substance - cannot be reliably and permanently ruled out in workplaces.
