Teledyne 2020 - Explosion proof thermal conductivity analyzer - Manual (Page 32)

Teledyne Analytical Instruments
3 Installation Model 2020
3-14
NOTE: An additional option is available for SEALED reference appli-
cation. This option would not have the reference Gas Flow
Meter, Piping and Fittings.
3.4.2 Pressure and Flowrate Regulation
Appropriate pressure reducing regulators must be installed at all gas
supply sources. 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.
The gas pressure in should be reasonably well regulated. Pressures
between 5 and 50 psig are acceptable (10 psig is normal) as long as the
pressure, once established, will keep the flow constant during analysis
and within an acceptable range (between 0.1 and 0.4 scfh—See Note).
Note: Gases lighter than air have a flowrate higher than indicated
on the flowmeter, while gases heavier than air have a flowrate
lower than indicated. Values can range from one half to twice
the indicated flowrate.
For example: For hydrogen or helium, set the flowrate to 0.1
scfh (50 cc/min). For carbon dioxide or argon, set the flowrate
to 0.4 scfh (200 cc/min).
When installing pressure regulators on supply cylinders, crack the
cylinder valves so that gas is flowing during installation. This will elimi-
nate the most common cause of standardization-gas contamination: air
trapped during assembly diffusing back into the cylinder. This procedure is
particularly important in applications where impurity content of 1 to 2 % is
the range of interest.
Note: If you have the –V option, The above pressure and flow
values apply instead to the vacuum at the VENT connector,
described below, with minus signs before the pressure
readings.
3.4.3 VENT Exhaust
There are two separate VENT fittings—one for the sample gas and
one for the reference gas . Use 1 /
4
inch tubing for both sample and reference
vents to minimize back pressure from restricted flow.
Exhaust connections must be consistent with the hazard level of the
constituent gases. Check local, state, and federal laws, and ensure that the
exhaust stream vents to an appropriately controlled area if required. If not
vented to the same area, both VENT lines must vent to areas with equal