Teledyne T200 Operation Manual page 242

Troubleshooting & Service
12.4.1.3. HIGH FLOW
12.4.1.4. SAMPLE FLOW IS ZERO OR LOW BUT ANALYZER REPORTS CORRECT FLOW
240
Teledyne API – T200 NO/NO2/NOx Analyzer Operation Manual

Be very cautious when handling the dryer fittings (see Section 11.3.2 on proper
handling instructions).

If the filter is clogged, replace it with a new unit.

If taking off this filter does not solve the problem, continue to the next step.

Do not leave the dryer without filter for more than a few seconds, as you may
draw in dust, which will reduce the performance of the dryer.
4. A leak between the flow meter and the reaction cell (where the flow-determining
critical orifice is located) may cause a low flow (the system draws in ambient air
through a leak after the flow meter).

Check for leaks as described in Section 11.3.12.

Repair the leaking fitting, line or valve and re-check.
5. The most likely cause for zero or low ozone flow is a clogged critical flow orifice or
sintered filter within the orifice assembly.

The orifice that sets the ozone flow is located on the reaction cell.

Check the actual ozone flow by disconnecting the tube from the reaction cell
and measuring the flow going into the cell.
If this flow is correct (~80 cm³/min), the orifice works properly.

If this flow is low, replace the sintered filter.


The orifice holder assembly allows a quick and easy replacement of the filter
(see Section 11.3.5 and on for replacement procedures).

Appendix B lists a spare part kit with a complete orifice assembly that allows a
quick replacement with minimum instrument down-time.
Flows that are significantly higher than the allowed operating range (typically ±10-11%
of the nominal flow) should not occur in the T200 unless a pressurized sample, zero or
span gas is supplied to the inlet ports.

Ensure to vent excess pressure and flow just before the analyzer inlet ports.
When supplying sample, zero or span gas at ambient pressure, a high flow would
indicate that one or more of the critical flow orifices are physically broken (very
unlikely case), allowing more than nominal flow, or were replaced with an orifice of
wrong specifications.

If the flows are within 15% higher than normal, we recommend measuring and
recalibrating the flow electronically using the procedure in Section 10, followed by a
regular review of these flows over time to see if the new setting is retained properly.

Also, check the flow assembly o-rings and replace as needed.
Note that the T200 analyzer can report a correct flow rate even if there is no or a low
actual sample flow through the reaction cell.

The sample flow on the T200 is only calculated from the sample pressure and
critical flow condition is verified from the difference between sample pressure and
vacuum pressure.
06858E DCN7057