Description of the safety-related DustEx parameters
In industrial facilities with combustible dusts, there is always a risk of explosion. The requirement for this is a certain concentration of dust in the air in conjunction with a potential ignition source. The primary focus should therefore remain on measures that reduce the amount or concentration of dust in a workplace (cleaning, extraction).
Companies are responsible for analysing and minimising the risk of dust explosions (Directive 1999/92/EG). This includes a detailed analysis of the safety-related dust characteristics and a comprehensive classification of the working environment into zones.
Dusts behave differently to gases and vapours
| Characteristics of the flammable substances | Gases, Vapours (G) | Dusts (D) |
| Miscibility with air and demixing | Good, permanent No, difficult | Due to air flow, limited in time Sedimentation due to gravity |
| Density difference to air and particle size | Relatively low, Molecule (e. g. CH 4) | Large, Dependent on technical condition |
The safety definition for dusts is usually more complex than for gases and vapours. As a general rule, the finer the dust, the higher the risk.
Knowledge of the essential safety-related dust explosion protection parameters and the ambient conditions (e.g. temperature) is crucial for the necessary level of protection and therefore the selection of suitable Ex equipment. Depending on the temporary behaviour of the explosive dust atmosphere (cloud), Ex areas are categorised into zones:
| Conditions and zones | Requirements for equipment | ||||
|---|---|---|---|---|---|
| The explosive dust atmosphere (cloud) is … | Classification Ex-Areas | Group (Directive 2014/34/EU) | Equipment category (Directive 2014/34/EU) | Equipment group (IEC 60079-0 ff. & ISO 80079-36) | Equipment protection level (EPL) (IEC 60079-0 ff. & ISO 80079-36) |
| Constant, long-term or frequent presence | Zone 20 | II | 1 D | III | Da |
| in normal operation occasionally | Zone 21 | II | 2 D or 1 D | III | Db or Da |
| in normal operation normally not or only for a short time | Zone 22 | II | 3 D or 2 D or 1 D | III | Dc or Db or Da |
Any questions? We will assist you promptly.
Sign up for our Newsletter now: