Using Nafion Dryers with a Vacuum Pump or Eductor to dry sample gas
Most of our OEMs use our dryers with the purge under a vacuum to drive the differential in water vapor pressure across the membrane, for two main reasons. First, no external source of dry, clean air is required. Second, when set up correctly, it is a very cost effective and reliable solution. There are four ways you can set up Perma Pure Dryers to work under vacuum.
For best dryer system performance, the optimal performance point of flow and vacuum level should be achieved as shown in the diagram below. Every combination of flow rate, dryer and vacuum pump or eductor will have its own unique performance characteristics – for any given combination, this point must be found. This is done by continually restricting the flow of the purge glass by closing the needle valve while watching the moisture level at the DP Sensor located at the sample gas outlet. The “sweet spot” or optimal performance occurs when the vacuum is at its highest point (the lowest pressure) and the flow rate is still high enough to sweep the water vapor away.
Note: During testing, it might take up to 30 minutes or more for the dryer performance to stabilize in order to make a performance determination – you may not see immediate changes and this could be confusing.