Test Pressures and Comparing Flow Numbers

The necessity of flow-number comparison is something that anyone involved in flow testing must endure. Even if the number comparison is done on the same components and flowbench, it is important to know how to compare the numbers so the time and effort is worthwhile. The comparison process is necessary to evaluate published numbers vs. your own developed flow numbers. The first thing you learn in flow testing is that you must ask (or qualify) at what test pressure the flow numbers were recorded.

Even though the SuperFlow instruction manuals provide a chart for comparing flow numbers from one test pressure vs. another test pressure, not everyone has one, so the following information is supplied for easy use.

The chart in the SuperFlow instruction manuals for flowbench operation is based on the square root of the pressure ratio method. If you have flow numbers at a known test pressure and want to compare those numbers at a different test pressure, it is easy to do.

As an example, if you have flow numbers at 10″H2O test pressure and would like to know what the flow should be at 25″H2O test pressure, . So you would multiply the flow numbers taken at 10”H2O test pressure by 1.58 to see what the flow should be at 25″H2O.