Basics of Explosion Protection Explosion Protection; Classification of Zones

Flammable gases, mists and dusts, together with professional oxygen, formexplosive atmospheres. If such an atmosphere is ignited, anexplosion result, which may cause serious damage to personnel and equipmentAn explosion can only take place if the following factors arejointly active: •flammable substance (professional gas, vapour, mist or dust) in a suitable distribution and concentration•oxygen (from the air) and•ignition sourceAn explosion atmosphere only occurs if the substance-airmicture lies within a certain concentration range, the explosion limits. The explosion limits depend on the ambient pressureand the oxygen concentration of the air.
02207E02 Explosion Protection In order to avoid explosions and associated dangers, an operator must incorporate effective explosion protection precautions into his plant.The principle of integrated explosion requires that explosion protection measures be taken in the following order: •Measures to prevent formation of a dangerous explosive atmosphere•Measures which prevent dangerous explosive atmospheres from igniting•Measures which restrict the effects of an explosion to a safe level So are distinguished:•Primary explosion protection:all measures which prevent the formation of an explosive atmoshpere•Secondary explosion protection:all measures which restrict the effects of an explosion to an insignificant level•Explosion-resistant constructionthese are the measures taken to reduce the effects of an explosion to a negligible minimum Classification of Zones Hazardous areas are classified into Zones, depending on thecomposition and presence of an explosive atmosphere. Thisenables both selection of suitable equipment and appropriateelectrical installation.Electrical apparatus for use in hazardous areas are assigned to various categories. The additional character G (gas) or D (dust) specifies whether the electrical apparatus may be installed in gas and dust endangered areas. Classification of Zones and use of equipment Zone 0 Equipment with type examination certificate Zone 1 Equipment with type examination certificate Zone 2 Equipment complying with the basic requirements of Directive 94/9/EC (Equipment certified for Zone 0 and 1 can also be used). category 1Gcategory 1DZone 1Zone 21 Zone in accordance with EC directive 99/92/EGPresence of potentially explosive atmospheresSafety level of deviceEquipment category in accordance with EC directive 94/9/EGZone 0Zone 20 continuouslyorfor long periods orfrequentlyvery high level of protection occasionallyhigh levelof protection category 2Gcategory 2DZone 2Zone 22 category 3Gcategory 3D infrequently and for only a short periodnormal levelof protection

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General Catalogue 13.02.2006