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Instrument Maintenance Teledyne API - Model T200H/T200M Operation Manual
214
6.3.6. CHANGING CRITICAL FLOW ORIFICES
There are several critical flow orifices installed in the T200H/M, Figure 6-4 shows one
of the two most important orifice assemblies, located on the reaction cell. Refer to
Section 8.3.3 for a detailed description on functionality
and locations. Despite the fact
that these flow restrictors are protected by sintered stainless steel filters, they can, on
occasion, clog up, particularly if the instrument is operated without sample filter or in an
environment with very fine, sub-micron particle-size dust.
The T200H/M introduces an orifice holder that makes changing the orifice very easy. In
fact, it is recommended to keep spare orifice holder assemblies at hand to minimize
downtime and swap orifices in a matter of a few minutes. Appendix B lists several
complete spare part kits for this purpose.
To replace a critical flow orifice, do the following:
1. Turn off power to the instrument and vacuum pump. Remove the analyzer cover
and locate the reaction cell (Figure 3-7 for location in chassis, and Figure 6-4 for
explode
d view of assembly).
2. Unscrew the 1/8” sample and ozone air tubes from the reaction cell
3. For orifices on the reaction cell (Figure 6-4): Unscrew the orifice holder with a 9/16”
wre
nch. This part holds all components of the critical flow assembly as shown in
Figure 6-5. Appendix B contains a li
st of spare part numbers.
4. For orifices in the vacuum manifold: the assembly is similar to the one shown in
Figure 6-5, but without the orifice holder, part number 04090, and bottom O-ring
OR3
4 and with an NPT fitting in place of the FT 10 fitting. After taking off the
connecting tube, unscrew the NPT fitting.
Figure 6-5: Critical Flow Orifice Assembly
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.
07270B DCN6512