1.2 Sample system guidelines
The
HygroPro
transmitter can be installed in a sample
system or directly in the process line. However, Panametrics
recommends that the unit be installed in a sample
system to protect the probe from potentially damaging
components in the process stream.
Figure 1
below
shows a typical sample system.
HygroPro
Probe
Needle
valve 1
Needle
valve 2
Flow cell
Flo
w
See note below
Intake near the center of the
pipe is recommended.
Figure 1: A typical sample system
Note:
At least 5 ft (1.5 m) of 1/4” (6 mm) tubing vented
to atmosphere will ensure an accurate process sample
and avoid diffusion of ambient air moisture back into
the process.
In the sample system shown in Figure 1 on page 2,
fully open
valve 1
and use
valve 2
to regulate the sample
flow for measurements at process system pressure.
For measurements at atmospheric pressure, fully open
valve 2
and use
valve 1
to regulate the sample flow.
Before constructing a sample system, consult a Panametrics
application engineer and observe the following guidelines:
• The sample system should be very simple and should
contain as few components as possible. All or most of
those components should be located downstream
of the measurement point.
• Sample system components must not affect moisture
readings. Most common filters and pressure regulators
are not suitable for sample systems because the wetted
parts adsorb moisture or release moisture into the sample
system. They may also allow ambient contamination to
enter the sample system. If possible, use stainless steel
for all wetted parts.
• The HygroPro probe should be oriented perpendicular
to the sample system inlet. For dimensions and
other sample system requirements see "Mechanical
• Sample systems should be tested for leaks prior to
operation, using a
Snoop
leak detector, to verify the
integrity of connections, components and fittings.
IMPORTANT
When pressurizing or depressurizing the sample system,
be careful to avoid shock damage to the moisture sensor.
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