The flowing gas dilution system is shown in the figure here. This device will acquire gas samples from all types of sources--hot, cold, concentrated, dilute, flowing or static. The dilution cools the sample and prevents water condensation, thus eliminating any need for heated gas cells and high temperature reference spectra.


Nitrogen is recommended as the dilution gas. Use plastic tubing to connect a nitrogen tank to the Dilution Gas Inlet. With positive pressure, cause the nitrogen to flow. Both flowmeters will give the same reading.

Next, connect the sample line to the Sample Inlet. This could be a heated metal sample line or just a plastic room- temperature sample line, depending on the application. The sample will probably be at one atmosphere pressure, so that the sample will not flow and both flowmeters will still have the same reading.

Connect the Diluted Sample Outlet to the infrared absorption cell. Then slightly reduce the pressure in the cell to cause sample flow. The flowmeter marked Diluted Sample Flow will then go to a higher reading than the flowmeter marked Dilution Gas Flow. The dilution factor is controlled by adjusting the input pressure of dilution gas and the pressure reduction in the absorption cell.

The dilution factor is calculated by dividing the dilution gas flow by the difference in the flowmeter readings. . For example, if the dilution gas flow is 8 liters per minute and the diluted sample flow is 10 liters per minute, then the sample flow is 2 liters per minute and the

Return to Table of Contents