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Teledyne Analytical Instruments
16
Thermal Conductivity Analyzer Model 212R
The reference and sample flowrates should be checked daily. The instru-
ment is somewhat flow sensitive. Operating on Range #1 a change in flowrate of
0.1 scfh will cause a corresponding change in sensitivity of from 1 to 20% of
scale. On the coarser ranges, the change in sensitivity would be undetectable.
The sample path flowrate should be maintained at 0.3 scfh, the reference
path flowrate at 0.1 scfh, and the bypass flowmeter float should be slightly above
the bottom of the indicator glass.
4.2 Supporting Gas Supplies.
Supporting cylinder gas supplies should be checked frequently on a routine
basis with particular attention focused on the reference gas. A spare cylinder of
reference gas should be available at all times. When the cylinder pressure drops
below 100 psig the reference supply should be replaced as the operation of the
regulator is questionable at pressures below this point.
When replacing supply cylinders, be sure to bleed the gas through the
cylinder valve while installing the pressure regulator (see Section 2.3.4). It is
also advisable to check the connections with soap water whenever a supply
cylinder is changed.
4.3 Standardization.
The analyzer must be completely restandardized whenever the reference
gas supply is replaced. Barring unforeseen difficulties with the analyzer, re-
standardization should not be necessary between reference cylinder replacement
periods if the analyzer is run continuously. If the analyzer is shut down for long
period of time use the startup procedure (in its entirety) when operation is to be
resumed.
NOTE: TAI strongly recommends that the analyzer run con-
tinuously with gas flowing in both the sample and
reference paths. During inactive periods arrange the
input manifold so that zero gas is flowing. Gas sup-
plies can be conserved by reducing the sample and
reference path flowrates to less than 0.1 scfh and
closing off the bypass flow completely.