Teledyne 9110TH - Nitrogen Oxides Analyzer - Manual (Page 219)

Instrument Maintenance Model 9110TH NOx Analyzer
Teledyne Analytical Instruments 199
5. Take out the components of the assembly: a spring, a sintered filter, two O-rings
and the orifice. 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.
6. Discard the two O-rings and the sintered filter and the critical flow orifice.
7. Re-assemble the flow control assembly with new the parts (see Appendix B for part
number or replacement kit) as shown in Figure 6-5 and re-connect them to the
reaction cell manifold or the vacuum manifold.
8. Reconnect all tubing, power up the analyzer and pump and - after a warm-up period
of 30 minutes, carry out a leak test as described in Section 7.5.
6.4.7. CHECKING FOR LIGHT LEAKS
When re-assembled or operated improperly, the 9110TH/M can develop small leaks
around the PMT, which let stray light from the analyzer surrounding into the PMT
housing. To find such light leaks, follow the below procedures. CAUTION: this
procedure can only be carried out with the analyzer running and its cover removed. This
procedure should only be carried out by qualified personnel.
1. Scroll the TEST functions to PMT.
2. Supply zero gas to the analyzer.
3. With the instrument still running, carefully remove the analyzer cover. Take extra
care not to touch any of the inside wiring with the metal cover or your body. Do not
drop screws or tools into a running analyzer!
4. Shine a powerful flashlight or portable incandescent light at the inlet and outlet
fitting and at all of the joints of the reaction cell as well as around the PMT housing.
The PMT value should not respond to the light, the PMT signal should remain
steady within its usually noise.
5. If there is a PMT response to the external light, symmetrically tighten the reaction
cell mounting screws or replace the 1/4” vacuum tubing with new, black PTFE
tubing (this tubing will fade with time and become transparent). Often, light leaks
are also caused by O-rings being left out of the assembly.
6. Carefully replace the analyzer cover.
7. If tubing was changed, carry out a leak check (Section 7.5).