Electrical Apparatus for Explosive Gas Atmospheres Part - 10: Classification of Hazardous Areas
|Publication Date:||1 June 2002|
|ICS Code (Electrical apparatus for explosive atmospheres):||29.260.20|
This part of IEC 60079 is concerned with the classification of hazardous areas where flammable gas or vapour risks may arise, in order to permit the proper selection and installation of apparatus for use in such hazardous areas.
It is intended to be applied where there may be a risk of ignition due to the presence of flammable gas or vapour, mixed with air under normal atmospheric conditions (see note 2), but it does not apply to
a) mines susceptible to firedamp;
b) the processing and manufacture of explosives;
c) areas where a risk may arise due to the presence of ignitable dusts or fibres;
d) catastrophic failures which are beyond the concept of abnormality dealt with in this standard (see note 3);
e) rooms used for medical purposes;
f) areas where the presence of flammable mist may give rise to an unpredictable risk and which require special consideration (see note 5);
g) domestic premises.
This standard does not take into account the effects of consequential damage.
Definitions and explanations of terms are given together with the main principles and procedures relating to hazardous area classification.
For detailed recommendations regarding the extent of the hazardous areas in specific industries or applications, reference may be made to the codes relating to those industries or applications.
NOTE 1 For the purpose of this standard, an area is a three-dimensional region or space.
NOTE 2 Atmospheric conditions include variations above and below reference levels of 101,3 kPa (1 013 mbar) and 20 °C (293 K), provided that the variations have a negligible effect on the explosion properties of the flammable materials.
NOTE 3 Catastrophic failure in this context is applied, for example, to the rupture of a process vessel or pipeline and events that are not predictable.
NOTE 4 In any process plant, irrespective of size, there may be numerous sources of ignition apart from those associated with electrical apparatus. Appropriate precautions will be necessary to ensure safety in this context. This standard may be used with judgement for other ignition sources.
NOTE 5 Mists may form or be present at the same time as flammable vapours. This may affect the way flammable material disperses and the extent of any hazardous areas. The strict application of area classification for gases and vapours may not be appropriate because the flammability characteristics of mists are not always predictable. Whilst it can be difficult to decide upon the type and extent of zones, the criteria applicable to gases and vapours will, in most cases, give a safe result. However, special consideration should always be given to the danger of ignition of flammable mists.