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Instruction Manual
HAS60E-IM-HW
June 2007
NGA 2000 CLD
3 - 13OperationEmerson Process Management GmbH & Co.OHG
3-6 CONVERTER TEMPERATURE ADJUSTMENT
The vitreous carbon converter used in this analyzer mod-
ule must be checked periodically to assure that it is work-
ing at peak efficiency. The efficiency of the converter is
typically 95 % to 98 %, that is, 95 % to 98 % of the nitro-
gen dioxide introduced to the module is reduced to nitric
oxide. That is well above the 90 % minimum required by
several Environmental Protection Agency.
Two conditions reduce the efficiency of the converter:
• The converter is operating at too low a tempera-
ture and the efficiency drops or
• The converter is operating at too high a tempera-
ture and the nitrogen dioxide is reduced to nitro-
gen, which is not detectable by the chemilumines-
cence reaction.
Initially, an interval of one week between converter effi-
ciency checks is recommended because high tempera-
ture operation changes conditions inside the converter.
The active surface area of the vitreous carbon increases
through use. Initially, when the surface area is low, the
temperature at which converter efficiency peaks is rela-
tively high. This peak temperature moves downscale as
surface area increases, and less external energy is re-
quired to cause adequate conversion.
The nominal range of converter operational tempera-
ture is 300 °C to 400 °C (572 °F to 752 °F). The current
converter temperature can be viewed in the "Physical
measurement" menu. To access the converter tempera-
ture adjustment:
Main (Menu)...
Analyzer and I/O expert controls & setup...
Analyzer module setup...
Physical measurements parameters...
Follow this procedure to optimize the operating tempera-
ture of the converter:
1. Power up the module and allow it to stabilize at
operating temperature (about one hour).
2. Check the Converter Temperature on the Physi-
cal Measurements menu (see Section 3-3).
Note the value for future reference.
3. Introduce a calibration gas of known (NO
2
) con-
centration into the analyzer and note concentra-
tion value determined when the full response has
been achieved.
4. Change Converter Setpoint in the "Temperature
Control" menu to 300 °C. Allow module 15 min-
utes to stabilize, recheck the concentration value
and note the value for later use.
5. Increase the Converter Setpoint value by 20 °C,
wait 15 minutes, and note the concentration value.
Repeat this step until either a converter efficiency
of between 95 % and 98 % is obtained or the final
20 °C increment produces an efficiency increase
of less than one percent.
6. Decrease the Converter Setpoint value by 5 °C,
which places the converter at a temperature suit-
able for low ammonia interference and efficient NO
2
conversion.
7. Recheck the Converter Temperature value in the
"Physical Measurements" menu, and compare it
to the initially recorded value.
NOTE
Converter temperature is not a direct measure of
converter efficiency. Temperature measurement is
for reference purposes only.