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Important Principles of Operation
2.1
Sensor Operating Principle
The nanopore sensor utilized in this analyzer measures the amount of water vapor molecules that
have entered its pores. This amount is directly proportional to the partial water vapor pressure in
the gas surrounding the sensor, and the partial water vapor pressure is dependant on the water
vapor content of the gas and the total pressure of the gas. Thus to compute the water vapor
content of the gas under measurement the analyzer has to “know” the total pressure of the gas.
Since there is no built-in pressure sensor, the user should enter the total pressure into the
analyzer, this can be easily done by entering atmospheric pressure (the analyzer default setting)
and measuring at atmospheric pressure by allowing the sample cell outlet (exhaust) port to vent
without restrictions.
2.2
Sampling Mechanism Operating Principle
The
PLMa
is intended to be installed in the user’s system or in a sample cell. The PLMa is
provided with 3/4”-16 parallel treads with O-ring seal, and with 1/4” Male NPT threads. See
Appendix A.
The
PLMaEx
is equipped with a built-in sampling system which has the required tight seals to
measure low moisture content; it consists of a stainless steel 100 micron filter and a flow control
orifice (which may be placed at either the inlet or outlet of the sampling cell or removed). The
gas under measurement is exposed only to the stainless steel walls of the sampling system. See
Appendix B.
The
PLMa-Probe-Ex
is the first and only moisture analyzer probe designed to directly insert
into a “live” pressurized pipeline, thus avoiding the need to shut down the pipeline when
inserting or removing for re-calibration or pipeline service. It has an all stainless steel
construction, is small enough to be installed on a 1/2” or larger Ball Valve, seals with
3/8“ Swagelok tube fittings and has sufficient travel for insertion even into the largest diameter
pipelines.
The Phymetrix PLMa-Probe-Ex meets the new environmental requirements of not exhausting
gas while making a measurement at a lower cost than an extractive sample system.
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