Classification of areas of places with the presence of flammable gases or vapors
In these, the formation of explosive atmospheres is possible at any time, for example there are areas for transferring explosive liquids, painting booths, solvent warehouses, etc.
They are further subdivided according to the probability of the explosive atmosphere being present in:
- Zone 0: permanent presence or for long periods of time.
- Zone 1: susceptible to form under normal working conditions.
- Zone 2: unlikely presence and for short periods.
The security principles to consider will be:
- Explosion risk areas will be as small as possible.
- The presence of electrical equipment will be minimized and will be of protection according to the area.
Places with presence of Combustible Dust
As an example we can cite grain silos, mills, coal treatment plants, fertilizer plants, etc.
Within this class it is distinguished:
- Zone 20: It is one in which there is or may be combustible dust during normal operation, start-up or cleaning operations, in sufficient quantity to produce an explosive atmosphere. Example: in pulverizer mills.
- Zone 21: It is the one in which the cloud or layer of dust is susceptible to form under normal working conditions.
- Zone 22: unlikely presence and for short periods.
The security principles to consider will be:
- Ventilation and thus the raising of dust should be avoided as much as possible.
- Cleaning maintenance and collection of dust generated periodically.
- Electrical equipment shall be protected against the ingress of dust to the required degree:
- IP5x. Protection against harmful ingress of dust.
- IP6x. Total protection against the ingress of dust.
- The maximum working surface temperatures of the equipment will be limited to 2/3 of the TIN or 745ºC less than the TIC for layers of 3 mm. If they are higher, this temperature must be reduced.