Teledyne T200, Operation Manual, Page: 243 / 425

Teledyne API
– T200 NO/NO
2
/NO
X
Analyzer Operation Manual Troubleshooting & Service
241

If the critical flow orifice assembly is partially or completely clogged, both the
sample and vacuum pressures are still within their nominal ranges (the pump keeps
pumping, the sample port is open to the atmosphere), but there is no flow possible
through the reaction cell.
Although measuring the actual flow is the best method, in most cases, this fault can also
be diagnosed by evaluating the two pressure values.

Since there is no longer any flow, the sample pressure should be equal to ambient
pressure, which is about 1 in-Hg-A higher than the sample pressure under normal
operation.

The reaction cell pressure, on the other hand, is significantly lower than under
normal operation, because the pump no longer has to remove 500 cm³/min of
sample gas and evacuates the reaction cell much better.

Those two indicators, taken together with a zero or low actual flow, indicate a
clogged sample orifice.
The T200 features a new orifice holder, which makes switching sample and ozone flow
orifices very easy; refer to Section 11.3.10 on how to change the sample orifices and to
Appendix B for part numbers of these assemblies.
Again, monitoring the pressures and flows regularly will reveal such problems, because
the pressures would slowly or suddenly change from their nominal, mean values.
Teledyne API recommends to review all test data once per week and to do an exhaustive
data analysis for test and concentration values once per month, paying particular
attention to sudden or gradual changes in all parameters that are supposed to remain
constant, such as the flow rates.
06858E DCN7057