16
Stainless Steel Air Motors
P1V-S
Introduction to the ATEX directive
Explosive atmospheres
Directive 94/9/EC defines an explosive atmosphere as a mixture of:
a)
flammable substances
– gases, vapours, mists or dusts
b) with
air
c) under specific
atmospheric conditions
d) in which, after ignition has occurred, combustion spreads to the
entire flammable mixture
(NB: with regard to dust, it may be that not all dust is combusted
after ignition has occurred)
An atmosphere with the potential to become an explosive atmosphere
during operating conditions and/or under the influence of the
surroundings is defined as a
potentially explosive atmosphere
.
Products covered by directive 94/9/EC are defined as intended for use
in potentially explosive atmospheres.
Harmonised European ATEX standard
The European Union has adopted two harmonised directives in the
field of health and safety. The directives are known as ATEX 100a and
ATEX 137.
Directive ATEX 100a (94/9/EC) lays down minimum safety
requirements for products intended for use in potentially explosive
atmospheres in European Union member states. Directive ATEX 137
(99/9/EC) defines minimum requirements for health and safety at the
workplace, for working conditions and for the handling of products
and materials in potentially explosive atmospheres. This directive
also divides the workplace into
zones
and defines criteria by which
products are
categorised
within these zones.
The table below describes the
zones
in an installation where there is a
potential for explosive atmospheres. The
owner
of the installation must
analyse and assess the area in which the explosive gas/dust mixture
may occur, and if necessary must divide it into
zones
. This process of
zoning then allows the correct plant and equipment to be selected for
use in the area.
The ATEX directive has been in force throughout the European Union
since 1 July 003, replacing the existing divergent national and
European legislation relating to explosive atmospheres.
Please note that for the first time, the directive covers mechanical,
hydraulic and pneumatic equipment and not just electrical equipment
as before.
With regard to the
Machinery directive
98/37/EC, note that a number
of external requirements in 94/9/EC refer to hazards arising from
potentially explosive atmospheres, where the Machinery directive only
contains general requirements relating to explosion safety (Annex I
1.5.7).
As a result, directive 94/9/EC (ATEX 100a) takes precedence over the
Machinery directive with regard to explosion protection in potentially
explosive atmospheres. The requirements in the Machinery directive
are applicable to all other risks relating to machinery.
Zones
Presence of potentially explosive atmosphere
Type of risk
Gas
Dust
G
D
0
0
Present continuously or for long periods
Permanent
1
1
Likely to occur in normal operation occasionally
Potential
Not likely to occur in normal operation but, if it does occur,
Minimal
will persist for a short period only
Zone 1
Category
Zone
Category 3
Zone 0
Category 1
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