Teledyne OT-3 - Manual (Page 28)

Installation OT-3
Teledyne Analytical Instruments 20
The vent line must be installed in a manner which will prevent dirt
and water from accumulating within the line. It must return sample to
atmospheric pressure. The vent line should be 1/4” diameter tubing or
larger and be at least 24” long. This will help to prevent the back
diffusion of O
2
into the sample system.
3.5 Sample System
The sample system used in the OT-3 Trace Oxygen Analyzer is a
robust gas handling and conditioning system designed for low flow rate
trace oxygen analysis in a natural gas or other low-oxygen gas
environment. It uses stainless steel tubing and fittings throughout and a
special 0-10 psig regulator designed to provide stable sample flow at
low volumes over wide temperature extremes. The incoming sample gas
is conditioned using a coalescing filter and an acid scrubber to remove
moisture and contaminants which would otherwise interfere with the
accurate trace analysis and/or reduce the lifetime of the sensor.
Refer to Figure 3-4 for the following discussion.
Note: Check the front of this manual for any additional
information in the form of addenda that may apply to your
custom system.
Sample gas enters the system at 5-2000 psig. A shut off valve is
installed and is used to switch gas flow on or off. The sample gas is
passed through a horizontal coalescing filter to remove moisture and
debris. This filter is designed to handle inlet gas pressure up to 2000
psig. It is important to periodically drain the condensate by opening the
drain valve. If appropriate, the drain line should be connected to a
suitable receptacle for handling contaminated waste liquid.
A 0-10 psig pressure regulator is installed downstream from the filter
and controls the sample pressure through the analyzer. In conjunction with
the flowmeter, it provides a stable mass flow even at low volume over the
rated temperature range of the instrument.
Set the pressure regulator to
provide a flow rate of 0.4 SCFH (approximately 4 psig).
A clear PVC acid gas scrubber is installed between the regulator
and the sample/span gas selector switch. The clear housing permits a
visual analysis regarding the condition of the scrubber medium and
allows the user to predict service intervals.
A switching valve is provided to feed the analysis unit with either
sample or span gas.