Gas Pathways
The colored lines that lead from the gas inlets through the analyzer and to the exhaust represent the current flow path. A different color path represents each gas source:
Pink | Loop gas |
Blue |
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Green | Preparation gas |
Black | Blended gas |
When a gas valve is opened, or the flow path is changed, it takes several minutes for the new gas to move through the entire system. |
The behavior of the loop valve is one example. When an analysis includes a loop injection, the schematic shows the path available in Fill mode, then Inject mode.
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In Fill mode, the analysis gas enters the loop, and the excess gas vents out the exhaust.
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In Inject mode, the analysis gas bypasses the loop and exits the analyzer through the exhaust.
At that time, the carrier gas path is available from the inlet all the way through the loop, through the sample tube, and past the detector.
When the valve switches to Inject mode, the quantity of analysis gas contained in the loop — one exact unit — is pushed out of the loop and through the sample tube by the carrier gas. When the application is recording the TCD signal, the loop injection shows as a peak on the Results view of the Analysis window.
The analysis gas may be greatly dissipated as it travels out of the loop and through the sample tube, particularly if the carrier gas flow rate is low. Higher carrier gas flow rates minimize the dispersion of the loop gas.