Teledyne 9110TH - Nitrogen Oxides Analyzer - Manual (Page 290)

Model 9110TH NOx Analyzer Principles of Operation
Teledyne Analytical Instruments 270
CE Mark safety screw), and should be changed according to the maintenance schedule
in Table 9-1.
8.3.5. OZONE GAS AIR FLOW
The excess ozone needed for reaction with NO in the reaction cell is generated inside the
analyzer because of the instability and toxicity of ozone. Besides the ozone generator
itself, this requires a dry air supply and filtering of the gas before it is introduced into the
reaction cell. Due to its toxicity and aggressive chemical behavior, O
3
must also be
removed from the gas stream before it can be vented through the exhaust outlet.
In contrast to the sample flow, the ozone flow is measured with a mass flow sensor,
which is mounted on the pneumatic sensor board, just behind the PMT sensor assembly.
This mass flow sensor has a full scale range of 0-1000 cm³/min and can be calibrated
through software to its span point (Section 4.13.7.5). As the flow value displayed on the
front panel is an actual measurement (and not a calculated value), the flow variability
may be higher than that of the sample flow, which is based on a calculation from (more
stable) differential pressures. On the other hand, the drift, i.e. long-term change, in the
ozone flow rate may be higher and usually indicates a flow problem. As with all other
test parameters, we recommend to monitor the ozone flow over time for predictive
diagnostics and maintenance evaluation.
CAUTION
Ozone (O
3
) is a toxic gas. Obtain a Material and Safety Data Sheet
(MSDS) for this gas. Read and rigorously follow the safety guide-
lines described there. Always make sure that the plumbing of the
O
3
generation and supply system is maintained and leak-free.