Teledyne 238 - Thermal conductivity analyzer - Manual (Page 11)

2-3 Teledyne Analytical Instruments
Thermal Conductivity Analyzer Installation 2
2.3.2 Vent Lines
The selected gas introduced into the sample path of the cell (zero,
span, and sample) is vented from one connection at the bottom of the
analyzer, and the reference gas is vented from another.
If it is desirable to carry these gases to an area remote from the ana-
lyzer to vent them, the following precautions will have to be observed in
vent line installation:
1. The vent lines should be constructed of 1/4 inch tubing, so that
no appreciable back pressure resulting from restricted flow is
experienced by the analyzer.
2. Both the sample and reference lines must be vented into an area
where the ambient pressure is the same.
3. The ambient pressure in the vent area must undergo no more
than normal barometric pressure changes.
4. The vent lines must be installed so that water and dirt cannot
accumulate in them.
2.4 Pressure Regulation
All incoming gas lines should be equipped with pressure regulators.
The sample line pressure regulator should be installed as close to the
sample point as possible to minimize sample line lag time.
Sample pressure should be set somewhere between 5 and 50 psig—10
psig is nominal.
To minimize flowrate adjustments, the pressure regulators on the
supporting gas supply cylinders should be adjusted to provide the same
output pressure as the sample line regulator.
When installing pressure regulators on supply cylinders, crack the
cylinder valves so that gas is flowing during installation. Using this proce-
dure will eliminate the most common cause of standardization gas contami-
nation. Air trapped during assembly can, and will, diffuse back into the
cylinder. This is particularly important in applications where impurities of 1
and 2% are the range of interest.