Teledyne 9110TH - Nitrogen Oxides Analyzer - Manual (Page 238)

Model 9110TH NOx Analyzer Troubleshooting & Repair
Teledyne Analytical Instruments 218
 Check the actual flow rate through the ozone dryer by using an external
flow meter to the inlet port of the dryer. This inlet port is inside the
analyzer at the end of the plastic particle filter (Section 6.4.2 for
illustration). If there is nominal flow (see Table 10-3 for flow rates),
consult Technical Support as there is a problem with the firmware or
electronics.
 If the actual flow is low or zero, check if the pump operates properly. The
RCEL pressure should be below 10 in-Hg-A at sea level. If it is above 10”,
rebuild the pump (Section 6.4.3). Check the spare parts list in Appendix B
on how to order pump rebuild kits.
 Check if the particle filter is clogged. Briefly remove the particle filter to
see if this improves the flow. Be very cautious about handling the Perma
Pure dryer fittings - refer to Section 6.4.2 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
Perma Pure dryer without filter for more than a few seconds, as you may
draw in dust, which will reduce the performance of the dryer.
 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 7.5. Repair the leaking fitting, line or valve and re-
check.
 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 (see Table 10-3 for flow rates), the
orifice works properly. If this flow is low, replace or clean the orifice. The
orifice holder assembly allows a quick and easy replacement of the orifice,
refer to Section 6.4.6 on how to do this. Appendix B lists a spare part kit
with a complete orifice assembly that allows a quick replacement with
minimum instrument down-time. The clogged orifice can then be cleaned
while the instrument is running with the replacement.
7.2.4. HIGH FLOW
Flows that are significantly higher than the allowed operating range (typically ±10-11%
of the nominal flow) should not occur in the 9110TH/M 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 to