Teledyne 9110EH - Nitrogen Oxides Analyzer - Manual (Page 233)

Model 9110EH Instruction Manual Troubleshooting & Repair
cumulative product of the NO
2
concentration times the exposure time to that
concentration). However, this lifetime heavily depends on many factors such as
absolute concentration (temporary or permanent poisoning of the converter is
possible), sample flow rate and pressure inside the converter, converter tempera-
ture, duty cycle etc. This lifetime is only an estimated reference and not a
guaranteed lifetime.
• In some cases with excessive sample moisture, the oxidized molybdenum metal
chips inside the converter cartridge may bake together over time and restrict air flow
through the converter, in which case it needs to be replaced. To avoid this problem,
we recommend the use of a sample gas conditioner (Section 5.9). Section 9.3.8
describes how to replace the NO
2
converter cartridge.
• With no NO
2
in the sample gas and a properly calibrated analyzer, the NO reading is
negative, while the NO
2
reading remains around zero. The converter destroys NO
and needs to be replaced.
• With no NO
2
in the sample gas and a properly calibrated analyzer, the NO
X
reading is
significantly higher than the actual (gas standard) NO concentration. The converter
produces NO
2
and needs to be replaced.
11.5.17. O
3
Generator
The ozone generator can fail in two ways, electronically (printed circuit board) and
functionally (internal generator components). Assuming that air is supplied properly to the
generator, the generator should automatically turn on 30 minutes after the instrument is
powered up or if the instrument is still warm. See Section 0 for ozone generator functional-
ity. Accurate performance of the generator can only be determined with an ozone analyzer
connected to the outlet of the generator. However, if the generator appears to be working
properly but the sensitivity or calibration of the instrument is reduced, suspect a leak in the
ozone generator supply air.
A leak in the dryer or between the dryer and the generator can cause moist, ambient air to
leak into the air stream, which significantly reduces the ozone output. The generator will
produce only about half of the nominal O
3
concentration when run with moist, ambient air
instead of dried air. In addition, moist supply air will produce large amounts of nitric acid in
the generator, which can cause analyzer components downstream of the generator to
deteriorate and/or causes significant deposit of nitrate deposits on the reaction cell window,
reducing sensitivity and causing performance drift. Carry out a leak check as described
earlier in this chapter.
11.5.18. IZS Option
The zero/span valves and IZS options need to be enabled in the software (contact the
factory on how to do this). See Figure 3-12 for a flow diagram with zero/span valve or IZS
option and Figure 3-2 to locate these options in the rear left corner of the instrument.
• Check for the physical presence of the valves or the IZS option.
• Check front panel for correct software configuration. When the instrument is in
SAMPLE mode, the front panel display should show CALS and CALZ buttons in the
second line of the display. The presence of the buttons indicates that the option has
been enabled in software. In addition, the IZS option is enabled if the TEST functions
show a parameter named IZS TEMP.
M9110EH Rev 0 219