An accepted method of leak testing a test piece is by using a differential measurement between it and a reference such as in the schematic here - why might one bother doing this as opposed to just comparing your test piece alone to a predefined or recorded leak rate, or curve?

  • $\begingroup$ I would imagine for the sake of speed and accuracy, especially for large vessels/pipes. Using some of the "classic" methods like pressure decay, vacuum decay or hydrostatic tests can take forever with a really small leak or a large volume (large pressure vessel or long pipeline) and also gets progressively less accurate the larger the volume/vessel tested. $\endgroup$
    – Gwyn
    Jul 15, 2020 at 12:32
  • $\begingroup$ @gwyn good point, I think being able to get more accurate and precise decay rates by doing it differentially rather than just a gauge measurement is probably the main reason in reality $\endgroup$ Jul 20, 2020 at 20:38

1 Answer 1


Pressures change in a vessel based on ambient conditions. The reference volume removes that source of error.


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