PN 903-8797, Rev A
For most applications, AMETEK recommends that the analyzer be operated
with the Bypass Valve open, although applications with measurements at pipe-
line pressures of 700 KPAG (100 PSIG) or less should be made with the Bypass
Valve closed. During the measuring cycle, the lower ow will create pres-
sure decreases throughout the sample system. At the low pipeline pressures,
the decreases are signicant enough to aect the accuracy of the dewpoint
measurement. When the analyzer is operated with the Bypass Valve open,
longer purging times are often required to eectively clean the Measuring Cell
between measuring cycles. Larger quantities of liquids will also be condensed
during the Cooling Stage.
When operating at very low pressures below 2000 KPA (300 PSIG) and
with large quantities of liquid droplets present in the gas stream, the
ow through the drain Flow Restrictors in the Filterblock Assembly
may be insucient to remove all liquid.
At low pressures, it is advisable to install an additional coalescing lter with a
valve or Flow Restrictor upstream of the analyzer to provide a constant drain.
Alternatively, a probe – such as a Genie – with an integral lter can be used.
Each of the three sections that make up the Filterblock Assembly contains a
Flow Restrictor. The Flow Restrictors drain ltrate from the upstream side of
the lter and also provides a fast loop to improve measurement response time.
This ensures there will always be a fresh gas sample in the Measuring Cell to
coincide with any process changes that may occur during any delay periods
introduced during the measuring cycle. Therefore, the response time is im-
proved because the analyzer will not have to wait for an older sample to be
purged out.
When there are no liquids present in the stream, the combined ow through
the three Flow Restrictors in the Filterblock Assembly will be approximately
1.5L/minute (3.5 SCFH) at 7000 KPA (1000 PSI) of gas pressure. If liquids are
present, the ow through the restrictors will be slightly lower.
2-38 | 241CE II Hydrocarbon Dewpoint Analyzer
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