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dust-explosion protection

The basics of dust-explosion protection - 9224 4 dust explosion protection measures

12 4. Dust Explosion Protection Measures4.1 Preventive (Primary) Explosion Protectionby Avoiding an Explosive Atmosphere 4.2 Preventive Explosion Protection by Avoiding Effective Ignition Sources This measure prevents the hazardous explosiveatmosphere from being ignited. This can be achieved by: > Analysing potential ignition sources > Determining the necessary extent of protective measures The complexity of the processes that can lead to a dust explosion means that it is extremely difficult to assess the actual risks in dealing with explosive dust/air mixtures. This makes explosion prevention measures especially important. These are generally considered to mean avoiding or limiting the amount of a hazardous explosive atmosphere.One possibility is to reduce the concentration of the combustible substance to values below the “lower explosion limit” (see Table2), such as by mixing it with non-combustible products. Another option is to prevent the release of combustible substances or at least to limit it. Both of these measures can be effectively supported bythoroughandregular housekeeping and by implementing suitable construction measures (see p.15). If release cannot be avoided, the surrounding air with its oxygen can be replaced as a potential reactant by a non- combustible gas such as nitrogen (inertisation). However, high operational costs mean that thismethod is limited to a smallnumber ofspecial applications. If these measures cannot be provided at a justfiable cost, there are other effec- tive options of explosion protection available. > Using suitable equipmentFor this reason, measures against a possibleignition of a present explosive atmosphere are used. A precondition is that the workflow process in question be assessed in adequate detail for any possible ignition sources. The nature of the protective measures used andthe level of safety required depend on the hazardous zone in question. The probability of the existence of an explosive dust atmosphere and the zone classification of hazardous areas derived from it are important factors for deciding what protective measures are necessary (seeSection5).
R.STAHL Explosion protection