Каталог Weidmuller: Enclosures and Cable Glands

ATEX directive 1999/92/EC
Technical appendix
ATEX directive 1999/92/EC
Article 137 of the European Community Formation Treaty set out
the minimum standards in order to improve workers’ health and
safety, this can also be put at risk by explosive atmospheres. An
explosive atmosphere is a mixture of air and flammable gasses,
vapours, mists or dust under atmospheric conditions where,
following successful ignition, the burning process will propagate
throughout the whole unburned mixture.
The ATEX directive 1999/92/EC was transferred into national
law. Compliance with the minimum standards contained in this
directive does not guarantee that all relevant national laws are
met. It is possible for local regulators to introduce more stringent
requirements.
The employer is required, according to the ATEX directive
1999/92/EC, to take measures to ensure the health and safety
of the employees. One measure is the division of the area into
zones where explosive atmospheres could be present.
Unless the risk analysis conducted by the employer indicates
otherwise, all areas where an explosive atmosphere may be
present must be equipped with devices and protective systems
that meet the relevant category of the ATEX directive 94/9/EC.
In particular in these zones the following categories of equipment
should be used, as long as they are suitable for use with gases,
vapours, mists or dusts:
• In Zone 0 or Zone 20: category 1 devices,
• In Zone 1 or Zone 21: category 1 or category 2 devices,
• In Zone 2 or Zone 22: category 1, category 2 or
category 3 devices.
Zoning according to the ATEX directive 1999/92/EC
Zone 0
An area which has a potentially explosive atmosphere that is
a mixture of air and flammable gases, vapours or mists. The
mixture is either permanently present or frequently present over
long periods of time.
Zone 1
An area in which during normal operations a potentially explosive
atmosphere of air and flammable gases, vapours or mists
can occasionally form.
Zone 2
An area for which during normal operations there is at most only
a short-term occurrence of a potentially explosive atmosphere of
mixtures of air and flammables gases, vapours or mists.
Zone 20
An area where a potentially explosive atmosphere is present in
the form of a flammable dust cloud in the air. This cloud is
either permanently present or frequently present over long
periods of time.
Zone 21
An area where, during normal operations, a potentially explosive
atmosphere in the form of a flammable dust cloud in the air
can occasionally form.
Zone 22
An area where, during normal operations, a potentially explosive
atmosphere in the form of a flammable dust cloud in the air is
not normally present or only present for a short time.
For the risk assessment and as well as the zoning concept
described above, Ex devices themselves can be considered in
an alternative process which uses the equipment protection
level (EPL). These protective levels determine the internal ignition
risk of a device where the sort of applied protection does not
play a role.
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