In part one of this series, we considered the pros and cons of pressure-decay testing. In part two, we’ll take a close look at a leak-testing method called “differential pressure decay.” This method is similar to simple pressure-decay testing discussed in part one.

A more accurate variant of the pressure-decay method, differential pressure testing involves pressurizing a reference volume along with a test part. The pressure differential between the nonleaking reference volume and the test item is then measured by a transducer over time, as shown in figure 1. This method requires measuring pressure at two points in time to obtain a pressure change reading. It is an indirect method of measuring leakage rate because the time and pressure data must be converted into leakage rate. This method allows you to use a higher-resolution pressure transducer. 

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