30  AO2000 CONTINUOUS GAS ANALYZERS  |  OI/AO2000-EN REV. B 
 
 
 
Caldos25, Caldos27, Magnos206: Version for the 'Safety Concept' 
Purging of the thermostat chamber 
The thermostat chamber that encloses the analyzer is flushed with purge 
gas at a slight positive pressure. The purge curtain formed in this manner 
comprises all of the parts of the sample gas path. In the event of a leak in the 
sample gas path, the purge gas flows into the analyzer and, in this way, pre-
vents flammable gases from emerging from the analyzer module. 
The purge gas is introduced at a flow rate of 15 to 20 l/h and a positive 
pressure of p
e
 ≤ 50 hPa to the thermostat chamber. As a result of the capil-
lary, a positive pressure of p
e
 = 7 to 20 hPa is established. The purge gas flow 
is measured by a flow meter located downstream from a capillary in the 
sample gas path. The outlet pressure should be open to atmospheric pres-
sure. 
The signal from the flow sensor is monitored and evaluated by a function 
block application (see section "Monitoring of purge gas flow" (see page 32)). 
Purge curtain 
 
1 
Sample gas inlet 
2 
Sample gas outlet 
3 
Purge gas inlet thermostat chamber "Analyzer Purge In" 
4 
Purge gas outlet thermostat chamber, ex works tubed with 13 
13 
Purge gas inlet flow monitoring 
14 
Purge gas outlet flow monitoring "Analyzer Purge Out"