Connect To The Sample Gas - Emerson Rosemount 370XA System Reference Manual

System Reference Manual
7P00370-H01
3.8

Connect to the sample gas

The sample handling system controls how the gas sample is
extracted, conditioned, and transported to the analyzer and is critical
to the accurate and reliable performance of any gas chromatograph.
The basic principles of sample handling are as follows:
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In the typical natural gas application, any liquid or solid contamination
in the gas will tend to accumulate on the inside pipe walls, even if it is
"clean and dry" gas. To take a representative sample of the flowing
gas, insert a sample probe into the center third of the pipeline. A major
flow disturbance in the pipe, such as an elbow fitting or an orifice
fitting, will cause the contaminants to be temporarily mixed with the
flowing gas stream; therefore, if practical, place the probe greater
than five pipe diameters from such a flow disturbance to reduce the
amount of contaminants that may be extracted with the gas sample.
Once the sample is extracted, the gas should be passed through both
particulate and liquid filters to remove any remaining contaminants
before it enters the gas chromatograph.
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Take a representative vapor sample.
Control the pressure without causing components to condense.
Remove particulate and liquid contaminates.
Transport the sample to the GC while maintaining the
composition.
370XA Gas Chromatograph
APRIL 2014