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Model 9110T NOx Analyzer Instrument Maintenance
Teledyne Analytical Instruments 241
11.2. PREDICTIVE DIAGNOSTICS
Predictive diagnostic functions including failure warnings and alarms built into the analyzer’s firmware
allow the user to determine when repairs are necessary.
The Test Functions can also be used to predict failures by looking at how their values change over time.
Initially it may be useful to compare the state of these Test Functions to the values recorded on the
printed record of the Final Test and Validation Data Sheet, P/N 04490.
The following table can be used as a basis for taking action as these values change with time. The
internal data acquisition system (DAS) is a convenient way to record and track these changes. Use
APICOM (Section 8.1.1) to download and review this data from a remote location.
Table 11-2: Predictive Uses for Test Functions
FUNCTION EXPECTED ACTUAL INTERPRETATION & ACTION
RCEL
(pressure)
Constant to within
± 0.5 in-Hg-A
Fluctuating Developing leak in pneumatic system. Check for leaks.
Slowly increasing
Pump performance is degrading. Rebuild pump when pressure
is above 10 in-Hg-A.
SAMP
(pressure)
Constant within
atmospheric
changes
Fluctuating Developing leak in pneumatic system. Check for leaks.
Slowly increasing Flow path is clogging up. Replace orifice filters.
Slowly decreasing
Developing leak in pneumatic system to vacuum (developing
valve failure). Check for leaks.
OZONE FL
Constant to within
± 15
Slowly decreasing Flow path is clogging up. Replace orifice filters.
AZERO
Constant within
±20 of check-out
value
Significantly increasing
Developing AZERO valve failure. Replace valve.
PMT cooler failure. Check cooler, circuit, and power supplies.
Developing light leak.
O
3
air filter cartridge is exhausted. Change chemical.
NO
2
(Concentration)
Constant for
constant
concentrations
Slowly decreasing
signal for same
concentration
Converter efficiency may be degrading. Replace converter
components.
NO
2
with IZS Option
installed
(Concentration)
Constant
response from day
to day
Decreasing over time
Change in instrument response. Low level (hardware) calibrate
the sensor.
Degradation of IZS permeation tube. Change permeation tube.
Heavily fluctuating from
day to day
Ambient changes in moisture are affecting the performance.
Add a dryer to the zero air inlet.
NO
(Concentration)
Constant for
constant
concentration
Decreasing over time
Drift of instrument response; clean RCEL window. Check for
flow leaks or irregularities.
Note
It is recommended that the above functions be checked weekly.
11.3. MAINTENANCE PROCEDURES
The following procedures are to be performed periodically as part of the standard maintenance of the
9110T.