Changing Critical Flow Orifices - Teledyne T200H User Manual

Instrument Maintenance

6.3.6. CHANGING CRITICAL FLOW ORIFICES

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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.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 (see Figure 3-7 for location in chassis, and Figure 6-4
for exploded 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"
wrench. This part holds all components of the critical flow assembly as shown in
Figure 6-5. Appendix B contains a list 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
OR34 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:
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.
Teledyne API - Model T200H/T200M Operation Manual
Critical Flow Orifice Assembly
07270D DCN7141