ABB AO2000-Fidas24 - Limas11 IR, Uras26: Version for the Safety Concept

28 AO2000 CONTINUOUS GAS ANALYZERS | OI/AO2000-EN REV. B
Limas11 IR, Uras26: Version for the 'Safety Concept'
Purging the cell windows
Purge at a slight positive pressure flows through the sample cell windows of
the safety cell. In the event of a leak in the sample gas path, e.g. cracking of
the sample cell window, the purge gas flows into the sample cell and, in this
way, prevents flammable gases from emerging from the analyzer module.
The purge gas is introduced to the purge curtain at a flow rate of 15 to 20 l/h
and at a positive pressure of p
e
≤ 50 hPa. As a result of the capillary, a posi-
tive pressure of p
e
= 7 to 20 hPa is established. The purge gas flow is meas-
ured by a flow meter located downstream from a capillary in the sample gas
path. The outlet pressure should be open to atmospheric pressure.
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
p
1
p
2
Flow
2
15 / 6 4 / 3
Sample
g
as Pur
g
e
g
as
Sample cell
Limas11 IR Uras26
1 1
Sample gas inlet
2 2
Sample gas outlet
4 3
Purge gas inlet sample cell windows
"Analyzer Purge In"
5 6
Purge gas outlet flow monitoring
"Analyzer Purge Out"