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explosion protection

The basics of explosion protection - 9224 4.technical principles

16 4. Technical Principles4.1 Zone Classification Hazardous areas are classified into zones to facili-tate the selection of appropriate electrical appa- ratus as well as the design of suitable electrical installations. Information and specifications for the classification into zones are included in IEC 60079-10.The greatest potential risk has to be taken intoaccount when classifying the potentially explosive areas into zones and determining the necessary protective measures. If there is no expert (skilled person) available inthe company to verify the risk of explosion and to determine the necessary measures, it is recom- mended that a competent authority be turned to. The equipment used in the defined hazardous zone must meet the requirements of the relevant assigned category (see section 3.2.1). 4.2 Minimum Ignition Energy and Explosion Group Explosion groups The minimum ignition energy is the minimum energy just sufficient to ignite the most ignitable mixture.This characteristic has to be considered when selecting the apparatus.The measured value of the minimum ignition energy is indicated for dusts. Gases are divided into explosion groups. Apparatus are divided into two groups: > Group I: > Electrical apparatus for mines endangered by firedamp Group II: Electrical apparatus for other places liable to be endangered by explosive atmospheresIn the case of electrical apparatus in Group I (mining), it is assumed that the only flammable gas that can occur is methane, but combined with coal dust. Other flammable gases, which can also occur in these areas, must be further classified as shown in Group II.Electrical apparatus of Group II used in explosivegas atmospheres are further classified into explosion groups.
R.STAHL explosion protection