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Model 9110T NOx Analyzer Instrument Maintenance
Teledyne Analytical Instruments 257
1. Turn off power to the instrument and vacuum pump.
2. Remove the analyzer cover and locate the reaction cell (Figure 11-5 and Figure
11-6).
3. Unscrew the 1/8” sample and ozone air tubes from the reaction cell.
4. For orifices on the reaction cell (Figure 11-6): Unscrew the orifice holder with a
9/16” wrench.
This part holds all components of the critical flow assembly as shown in Figure
11-7.
Appendix B contains a list of spare part numbers.
5. For orifices in the vacuum manifold: the assembly is similar to the one shown in
Figure 11-7, except:
Without the orifice holder, P/N 04090, and bottom O-ring, P/N OR34 and;
With an NPT fitting in place of the FT 10 fitting.
6. After taking off the connecting tube, unscrew the NPT fitting.
7. Take out the components of the assembly:
spring
sintered filter
two O-rings
the orifice
Note For the vacuum manifold only, you may need to use a scribe or pressure
from the vacuum port to get the parts out of the manifold.
8. Discard the two O-rings and the sintered filter and install new ones.
9. Reassemble the parts as shown in Figure 11-7.
10. Reinstall the critical flow orifice assembly into the reaction cell manifold or the
vacuum manifold.
11. Reconnect all tubing, power up the analyzer and pump. After a warm-up period of
30 minutes, carry out a leak test as described in Section 13.3.12.
11.3.11. CHECKING FOR LIGHT LEAKS
When re-assembled or operated improperly, the 9110T can develop small gaps around the PMT, which
let stray light from the analyzer surrounding into the PMT housing. To find such light leaks, follow the
procedures below.