Emerson Process Management GmbH & Co. OHG
1-3
1
Techn. Description
X-STREAM XEFD
Instruction Manual
HASXEDE-IM-EX
07/2017
1.4 High Pressure Option / Purge Option
1.4 High Pressure Option / Purge Option
Normally flameproof housings are permitted
to operate under atmospheric conditions only,
that is within an ambient pressure range be
-
tween 800 and 1100 hPa.
For analyzers this pressure range also applies
to the gas pressure within the containment
system. While the lower limit is not critical,
the higher is, because it lowers the permitted
sample gas (and calibration gases) pressures
by 400 hPa, compared to general purpose
analyzers. This results in higher requirements
for the sample handling system, as it has to
safely reduce the process gas pressure to the
permitted range.
Another aspect to take care for when oper-
ating flameproof analyzers is the option of
applying a purge gas to the enclosure when
measuring low concentrations of gases, being
constituent of the ambient air: The ambient air
inside the analyzer enclosure cross interfer-
ese with the sample gas and influences the
measuring results. By purging the housing
with a gas free of the measured component,
this can be avoided, but could increase the
pressure inside the analyzer and so would
violate the atmospheric pressure condition.
X-STREAM flameproof analyzers have been
subjected to additional tests to support both
situations:
•
higher sample and calibration gas pres
-
sures
as well as
•
purging the housing with a gas for best
measuring results at low concentrations.
To permit this, special additional conditions
must be taken into account:
High sample and calibration gas pressures
Higher gas pressure is specified to be within
the range of 1100 hPa to 1500 hPa. The maxi-
mum permitted flow is 1,5 l/min, depending on
the installed measurement system lower limits
may apply.
The gas paths need additionally to be protected
by suitable inline flame arrestors, designed and
approved for the applied higher gas pressure
and for the area of installation. These flame ar
-
restors need to be installed outside the analyzer
and in addition to the flame arrestors provided
by the analyzer.
Note!
The external inline flame arrestors are not
subject of the analyzer certification and may
be provided by the customer, or optionally by
EMERSON.
A separate analyzer flame arrestor has to be
installed, operating as a breathing device and
limiting the pressure in the enclosure in case
of internal leakage.
Purging the housing to 1100 hPa (1.45 psig)
with clean gas when measuring low con-
centrations
The maximum permitted gas flow is 2 l/min. The
gas must be supplied via a separate flame ar
-
restor. Another flame arrestor must be installed,
operating as a breathing device and limiting the
pressure in the enclosure to below 1100 hPa
(1.45 psig).
EXPLOSION HAZARD
When making use of any of
above mentioned options, take
care of the special conditions
given in the technical data
section, and in Chapter 2
(Installation)!
