Teledyne 238 - Thermal conductivity analyzer - Manual (Page 12)

Teledyne Analytical Instruments 2-4
2 Installation Model 235 Series
2.5 Accessory Sample System Components
An integral gas selector panel is available as an option. This panel
mounts the gas controls on a panel where they can be operated conveniently
In applications where TBE furnishes an accessory gas control panel, or
a completely interconnected panel or cubicle system, installation can be
simply accomplished by using the supporting drawings included at the rear
of the manual. However, if the customer is selecting and interconnecting his
own gas system components, the following conditions should be adhered to:
1. Do not deviate from the system outlined in the piping schematic
when constructing your system.
2. Select a flowmeter capable of resolving 0.08 SCFH (40 to
50 cc/min) for the reference path of the analyzer.
3. Select a flowmeter capable of resolving 0.3 SCFH (150 cc/min)
for the sample path of the analyzer. (See Addendum A for
recommended flowmeter readings for gases heavier or lighter
than air.)
2.6 Recommended Flowmeter Readings for
Gases Heavier or Lighter Than Air
Due to the wide range of applications and gases that are measured with
the Thermal Conductivity Analyzer, the density of different sample gases
may vary considerably; for example, air is more dense than hydrogen. When
setting the sample and reference flowrate, note that gases lighter than air
will have an actual flowrate higher than indicated on the flowmeter, while
gases heavier than air will have a lower actual flowrate. The following chart
(with hypothetical figures) illustrates this fact:
GAS FLOWMETER ACTUAL
READING FLOWRATE
Lighter than air 0.3 SCFH 1.2 SCFH
Heavier than air 0.3 SCFH 0.2 SCFH
Air 0.3 SCFH 0.3 SCFH