Purge Gas Conditions; Differential Pressure Monitoring; Infallible Containments - Emerson ROSEMOUNT MLT 2 Upgrade Manual

MLT 2 / BINOS
1.3.5

Purge Gas Conditions

Purge gas:
Temperature: As ambient, but min. +20 °C to +35 °C.
Rated input pressure at inlet of Ex p device:
Maximum input pressure at inlet of Ex p device:
Minimum internal overpressure of the enclosure:
Maximum internal overpressure of the enclosure
during operation:
1.3.6

Differential Pressure Monitoring

For analyzers connected to flammable gases
(either sample gas or span gas) the operator
needs to ensure that the pressure within the
containment system always remains at mi-
nimum 50 Pa below the pressure within the
analyzer enclosure. This ensures that in case
of a leak the flammable gas does not enter
the enclosure.
An additional differential pressure switch must
be provided to monitor the pressure diffe-
rence. The switch's electric contact has to be
1.3.7

Infallible Containments

Infallible containments may be used alterna-
tively for measuring flammable gases instead
of using differential pressure monitoring:
Infallible containments are designed and
built using joints made by welding, brazing,
glass to metal sealing, eutectic or comparable
methods. This ensures that the containment
does not have any intentional leakage into
the pressurized enclosure and supersedes
1-8

100 F
1.3
• Inert gas (e.g. Nitrogen)
• Air (from an ex-free area)
Medium has to be dry and free from
dust, oil, corrosive or aggressive
components!
Technical Data
2000 to 4000 hPa (2 to 4 bar)
6900 hPa (6,9 bar)
1 mbar
25 mbar
connected to the purge system. In case the
pressure difference decreases below 50 Pa
the contact opens and the purge system shuts
down the analyzer.
The limit of 50 Pa is the lowest permissible
value given by the standards, higher values
are acceptable, too.
Electrical and mechanical connections are
shown in section 2 „Installation".
the differential pressure switch and the „50 Pa
overpressure condition" (see 1.3.6).
Infallible containments are currently available
for the measuring principle TC (thermal con-
ductivity). Pls. contact your local sales office
for more information.
If your analyzer provides an infallible contain-
ment, see the associated manual for more
information.
Emerson Process Management GmbH & Co. OHG
ATEX Instruction Manual
ETC01035
02/2008