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Teledyne Analytical Instruments
15
Thermal Conductivity Analyzer Model 212R
virtually instantaneous. Recovery is a function of how long it takes to purge the
sampling system upstream from the cell. Accelerating the sample path flowrate
will speed the response.
NOTE: TAI recommends that some bypass flow be permitted
at all times. The bypass throttle meter is a part of the
input manifold. Being so located means that the
throttle valve lies between the sample side of the cell
and atmosphere.
Without some bypass flow it is possible that atmo-
sphere could diffuse into the sample line. Do not
attempt to use the throttle valve as a shut off valve.
Jamming the valve will damage the metering needle.
3.8 Sample Mode.
After the analyzer has been standardized, switch the selector valve to
"Sample". Set the bypass flow so that the float is visibly elevated from the
bottom of the tube and then readjust the sample flowrate to 0.3 scfh. No
further adjustments are required.
NOTE: Although the bellows type valves used in the input
manifold are among the best available, TAI suggests
that the span gas be turned OFF at the cylinder when
not in use, and the span line relieved of pressure
before closing the analyzer span valve. Such a proce-
dure will eliminate any possibility of the span gas
diffusing into the sample path of the analyzer. Nor-
mally, the recommended span gas composition con-
tains a component of interest content of 3/4 the coars-
est range of analysis. The component of interest
content of the sample gas, on the other hand, is usu-
ally well within the finest range of analysis. Instrument
sensitivity in Range #1 is 100 times greater than in
Range #3. The user can readily see what even a
minute rate of span gas diffusion would do to the
validity of a Range #1 analysis.
4. ROUTINE OPERATION
4.1 Flowrates.