Perform the following test with the Direct-Integrity-Test (DIT) parameters in the software as listed in the manual.

- switch off feed pump and wait until feed-line pressure has decayed to atm (if feed-pump installed).

- perform an integrity test on each unit

- calibrate D(Base) as described below for each unit.

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The diffusive flow of air through the membrane D(Base) depends on several parameters (e.g. water temperature). The flow could be lower than 2 mbar/min per module as well. Filter 2 installed at site shows a dp during the test of 0 mbar/min in several occasions.

D(Base) therefor needs to be calibrated. To do so, we should do the following when at site:

Start an integrity test and monitor the displayed pressure decay during the test. Assuming, that the membranes are intact, the decay shown is due to diffusive air flow. Take the displayed value in bar (1bar = 14,5 psi), divide it by the duration of the integrity test (in this case 23 minutes), this results then in the "real" D(Base).

D(Base) is deducted from p(test) according to my latest knowledge of the software, therefor p(test) in the data-log of Filter (2) is <0 mbar/min several times.

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- re-perform the integrity test at turned off pumps on every unit
- re-perform the test at running feed-pump (normal operating mode)