Analyzer Versions Ex Px With Continuous Purging Or Ex Pz With Use Of The Containment System; Analyzer Versions Ex Nr With Restricted Breathing Enclosure; Pressurized Analyzers Ex Pz For Use In Hazardous Zone 2; Ex Tc Analyzer Versions With Dust Protection By Enclosure - Siemens 7MB2531 Operating Instructions Manual

Safety instructions
2.2 Analyzers in hazardous areas
The assessment of the safety level of the monitoring devices also includes faults in the pressure
and gas lines. When assessing the safety level of the monitoring devices, it is assumed that the
monitoring devices are independent of one another. When the monitoring devices are coupled
to perform an overall function, this must be guaranteed with a safety level of at least that of
Category 3 according to EN ISO 13849-1.
Alternatively, a comparable international standard can be taken as the basis for EN ISO 13849-1.
2.2.4.2 Analyzer versions Ex px with continuous purging or Ex pz with use of the
containment system
With gas/air mixtures above the LEL, fault tolerance of the containment system is not
guaranteed in the sense of EN/IEC 60079-2 since sample gas can be released into the pressurized
enclosure as a result of leaks (e.g. O-rings). However, this release can be assessed as limited. The
maximum quantity released is below 200 µl/min, and is guaranteed by the quality assurance
measures of the analyzer manufacturer when the analyzer is delivered.
Continuous purging of the Ex p enclosure must therefore be carried out following the pre-
purging phase. This guarantees that sample gas released by a leak is diluted to such an extent
that an explosive gas mixture cannot occur. The volume flow of the protective gas has therefore
been set to 1 l/min; this is more than 100 times the maximum quantity of sample gas released.
2.2.4.3

Analyzer versions Ex nR with restricted breathing enclosure

In analyzers with a restricted breathing enclosure (type of protection Ex nR), only sample gases
may be connected whose composition is below the lower explosion limit (LEL).
The introduction of combustible to occasionally explosive gas mixtures is not permitted with this
type of explosion protection!
The connections for the protective gas (purging gas) must be closed gas-tight!
2.2.4.4

Pressurized analyzers Ex pz for use in hazardous Zone 2

Combustible gases or gas/air mixtures whose composition is also occasionally above the lower
explosion limit (LEL) may not be connected to analyzers with simplified pressurized enclosures
(protection rating Ex pz). Gases may only be connected to the sample gas path pursuant to the
hazardous Zone 1 definition if the analyzer is fitted with a px purging unit.
The introduction of gas mixtures that are frequently or always explosive is not permitted with
this type of explosion protection!
The connections for the protective gas must be closed gas-tight if protective gas is not used for
the corresponding part of the analyzer.
2.2.4.5

Ex tc analyzer versions with dust protection by enclosure

Only sample gases whose composition is below the lower explosion limit (LEL) may be
connected to analyzers with dust protection by enclosure (protection rating Ex tc).
The introduction of combustible to occasionally explosive gas mixtures is not permitted with this
type of explosion protection!
The connections for the protective gas must be closed gas-tight!
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Compact Operating Instructions in accordance with EN 61010-1 and EN 60079-0
Compact Operating Instructions, 09/2018, A5E45779389002-01