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ATEX Instruction Manual
ETC01035
August 2005
MLT 2 / BINOS
®
100 F
Emerson Process Management Manufacturing GmbH & Co. OHG
P - 5
TERMS USED IN THIS MANUAL
ATEX
Directive 94/9/EC, commonly called the
ATEX („Atmosphères Explosibles“)
products directive.
Area Classification
Zone 1
Where ignitable concentrations of
flammable gases can exist some of the time
under normal operating conditions.
(A guideline value [not part of a standard ]
is 10 to 1.000 hours per year.)
Equipment to be used in Zone 1 has to be
classified Category 2.
Zone 2
Where ignitable concentrations of
flammable gases are not likely to exist under
normal operating conditions.
(A guideline value [not part of a standard ] is
less than 10 hours per year.)
Equipment to be used in Zone 2 has to be
classified Category 3.
External Explosion Protection
The „External explosion protection“ serves
to prevent penetration of explosive gas
mixtures into the analyzer enclosure. In
addition it avoids ignition on the surface. For
this reason the analyzer is purged with
protective gas and held at an internal
overpressure compared to the surrounding
atmosphere.
Internal Explosion Protection
The „Internal explosion protection“ serves to
prevent ignition of gas being present in the
analyzer’s Containment System (CS;
= sample gas path).
Dependent on the gas composition several
options are available:
• None required (if gas is noncom-
bustible),
• dilution by purge gas
and/or
• internal overpressure of the analyzer’s
enclosure compared to the CS.
Containment System
The part of the analyzer containing the gas
that may constitute an internal source of
release.
Explosion Protection
Lower Explosion Limit (LEL)
Volume ratio of flammable gas in air below
which an explosive gas atmosphere will not
be formed: the mixture of gas and air lacks
sufficient fuel (gas) to burn.
Upper Explosion Limit (UEL)
Volume ratio of flammable gas in air above
which an explosive gas atmosphere will not
be formed: the mixture of gas and air is too
rich in fuel (deficient in oxygen) to burn.