Gas Pathways
The colored lines that lead from the gas inlets through the analyzer and to the exhaust represent the current flow path. Each gas source is represented by a different color path:
Pink | Loop gas |
Blue |
|
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 that is available in Fill mode, then in Inject mode. In Fill mode, the analysis gas is shown entering the loop and excess gas is vented out the exhaust. In Inject mode, the analysis gas is shown bypassing the loop and exiting 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 that is 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 dissipated greatly 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.
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