Plasma Gas Analyzer
67 02001001A_9
Most of the time, when sampling Helium, if line temperature pressure and flow vary, reading
will also vary. The stabilization time with Helium is much longer than with Argon.
Points to remember when sampling Helium :
1. Keep a constant and high flow rate in the sampling line. Exhaust the excess flow
through a by-pass rotameter.
2. Close to sample point tap or connection, use a small stainless steel electropolish
with VCR connection only pressure regulator. The by-pass rotameter with its
valve will fix the line flow and the sample point pressure regulator will maintain the
line pressure constant.
3. The third parameter: temperature. If the line temperature varies, reading will also
vary due to change in equilibrium conditions, change in temperature when
sampling Helium will cause reading drift and recovery time will be long if sample
flow is low. The best result is achieved if you can heat trace the sampling line and
maintain the temperature between 60C and 75C. The temperature must be
constant.
4. Install the supplied trap at the analyzer inlet.
Use only electropolished stainless steel. Electropolishing is an electrochemical procedure
that satisfies the deficient ionic sites of surface metallic molecules. These ionic sites strongly
attract polar molecules causing a stronger adsorption effect at that site.
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