SEP 2005 MODEL 1000
EQUIPMENT DESCRIPTION
2-2
2.1 SAMPLING SYSTEM
A well designed, properly adjusted sampling system is essential to optimum performance of any gas
chromatograph. If a good sample is not obtained for analysis, the whole purpose of the system is
compromised.
The purpose of the sample handling system is to transfer a conditioned fluid sample that is
compatible with gas chromatography requirements.
The Sample Conditioning System (SCS) is located between the process stream and the Analyzer, and
is usually mounted on the lower portion of the Analyzer stand. It serves these purposes:
- Extracts final sample from the fast loop,
- Performs final filtration,
- Performs stream switching for a multi-stream Analyzer, and
- Adjusts the final pressure, temperature, and flow control on the selected sample
flowing to the sample valve.
The following points should be considered in selecting and installing a sampling system:
- Sample Paint
- Sample Volume and Flow Rate
- Sample Conditioning
- Contamination Precautions
- Valving
- Calibration Gas
2.1.1 Sampling Point Location
Gas samples must be representative of the process stream and must be taken from a location where
stratification or separation of components does not occur. The sampling point should be as close as
feasible to the Analyzer.
2.1.2 Sample Volume and Flow Rate
An adequate response time for sample analysis requires that sample volumes should generally be as
small as possible, and the flow rate between the sampling point and the Analyzer should be as high
as possible, consistent with accuracy. To minimize time lag and to prevent back diffusion, dryers
and filters in the sampling line should be as small as possible. When long sampling lines cannot be
avoided, flow velocity in the line can be increased by decreasing the downstream pressure.
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