Siemens ULTRAMAT 6F Manuale dell'attrezzatura aggiuntiva - Pagina 7
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1.4
Further safety measures
The sample gas and reference gas lines must terminate outside the hazardous area at a point with no
danger; sample gas lines can be returned to the sampling point.
When connecting combustible or non-combustible sample gases into the hazardous area, both the
sample gas inlet and outlet must be provided with a flame inhibitor.
When connecting combustible media, the sample gas supply must be interrupted after switching off
the analyzer and the pressurized enclosure or when the pressurization is actuated in the event of a
fault.
The maximum permissible sample gas pressure in the analyzer depends on the type of connected
gas, and is described in Section 2.3 "Sample gas input conditions".
1.4.1
Analyzer versions EEx p with "Compensation of losses resulting from leaks"
The containment system (sample gas path in the analyzer) is rated as without release if
- the gaseous medium is not combustible,
- the gaseous medium is combustible, but the gas concentration is always below the lower explosion
limit which must be guaranteed by a safety level of at least category 4 to EN 954,
- the gaseous medium is combustible, and the differential pressure between the housing and the
containment system is monitored. The pressure in the housing must always be at least 50 Pa above
the pressure in the containment system.
The differential pressure monitoring between the housing and the containment system must be carried
out with the following safety level:
- the pressure monitoring of the containment system by the system itself is at least category 1 to EN
954 (operational reliability) and the differential pressure monitoring between the containment system
and the protective gas of at least category 1 to EN 954, or
- the differential pressure monitoring between the containment system and the protective gas at least
corresponds to category 3 to EN 954 (fault tolerance, 1-fail-safe) without consideration of system-
dependent safety.
A comparable international standard can also be applied instead of EN 954.
The assessment of the safety level of the monitoring device also comprises faults in the pressure or
gas lines. When rating the safety level of the monitoring device, it is assumed that the monitoring
devices are independent of one another. When linking the monitoring device into a total function, this
must be guaranteed with a safety level of at least category 3 to EN 954.
1.4.2
Analyzer versions EEx p "With continuous purging"
With gas/air mixtures above the LEL, fault tolerance of the containment system is not guaranteed in
the sense of EN 50016 since sample gas can be released into the pressurized housing 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 EEx p housing must therefore be carried out following pre-purging. 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 released.
E-4
Additional Equipment Manual EEx p
Order No.:
A5E 000
58873-02