Specifications
S
TARTUP AND
O
PERATION
748410-A
August 1999
22
Chemiluminescense Detector Analyzer Module
Rosemount Analytical NGA 2000
3
In the initial measurement, after lowering the temperature setpoint in Step 2, the
efficiency will normally be less than 92%.
14. Reset converter temperature setpoint 20
°
C higher, wait 15 minutes for temperature
equilibration, and measure conversion efficiency by repeating Steps 3 through 13.
Conversion efficiency should be improved.
15. Repeat Step 14 until: a) 95% to 98% efficiency is attained or b) the final 20
°
C converter
temperature adjustment yields an increase in efficiency of less than 1%.
16. Reset converter temperature setpoint 5
°
C lower. Converter temperature is now set to the
front edge of the plateau on the efficiency-vs.-temperature curve. (See Figure 3-8.) This
setting should provide the optimum combination of high conversion efficiency and low
ammonia interference.
17. Wait 15 minutes for temperature equilibration, and check converter temperature.
Compare present temperature with original value. Normally, converter temperature
should be in the range of 300
°
C to 400
°
C (572
°
F to 752
°
F).
3.7.3 S
UBNORMAL
C
ONVERSION
E
FFICIENCY
If a measured conversion efficiency of between 95% and 98% is unobtainable within the
normal temperature range, the most probable cause is depletion of the catalytic material
within the converter.
However, before concluding that the converter is defective, ensure that the conversion
efficiency measurement is accurate. Though the measured efficiency is less than the 95% to
98% range, the actual efficiency may be somewhat higher.
An apparent subnormal efficiency can be due to a problem external to the Analyzer Module,
perhaps located either within the test setup or between it and the Analyzer Module. Check
the following:
1. Leakage.
2. Loss of NO
2
between test setup and Analyzer Module. Such loss can occur by reaction
with a rubber diaphragm in a pressure regulator or flow controller. Stainless steel
diaphragms are preferred. Loss can also occur during passage through filter media.
NOTE