Section 4 Air Purge System; Air Purge Connection - Hach 2100N Instruction Manual

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SECTION 4
4.1

Air Purge Connection

Note: Do not exceed 138 kPa
(20 psig).
Figure 9 Air Purge Connections
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AIR PURGE SYSTEM
An air purge system is provided to purge the optical compartment with dry air to
prevent condensation on the outside of the sample cell when measuring cold
samples. This system is particularly useful when using Flow-Cell assemblies.
Dry nitrogen or instrument grade air (ANSI MC 11.1, 1975) up to 138 kPa
(20 psig) can be used to air purge the optical housing compartment. The
recommended air consumption rate is between 3 and 10 SCFH (standard cubic
feet/hour). The connection is made at the
When the sample temperature is expected to be near or below 2 °C (35 °F), use a
desiccant dryer and particle filter in the air line to ensure the dew point of the air
purge is below the sample temperature (see Figure 9).
If only shop air is available, use a coalescing filter with automatic drain in
conjunction with a dryer and particle filter to achieve instrument quality air. Life
expectancy of the coalescing filter should exceed 2000 hours. Change the particle
filter at the same time as the air dryer. Figure 9 illustrates methods of connecting
the two types of air supply to the instrument. The dryer and filter are not necessary
if dry nitrogen is used for the air purge.
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fitting on the rear panel.
AIR PURGE