The following description it is not intended as an instruction for use, but rather a summary on the test.
Refer to section 4.6, page 31 “System and Membrane Cassette Integrity Test” of the T-series Cassette Care and Use Procedure USTR 2433b for detailed instructions and the image for the connections.
This Integrity test method is recommended for ultrafiltration membrane with a Molecular Weight Cut-Off (MWCO) of≤ 300 kDa.
1.1 General Procedure
The cassette should be fully wetted out with water prior to conducting the integrity test. A clean compressed air source should be connected to the feed line, with an isolation valve between the pump and the air inlet line. The compressed air source requires a regulator that can be controlled to the recommended test pressure with a mass flow meter installed in the air line upstream of the filter. Alternatively, an integrity test instrument can be used if it is capable of measuring the require diffusive flow.
Ensure that the system is fully drained. Set the pressure on the regulator or integrity test instrument to the specified test pressure for the specific membrane being used. The retentate valve and the isolation valve between the pump and air inlet should be completely closed, with the permeate valve completely open.
Turn on the air supply to slowly (~15 - 30 seconds), pressurize the system to the recommended test pressure. The diffusive flow rate will initially increase before it drops and levels off at a stable flow rate.If this stable flow value is below the maximum allowable value for the particular membrane being tested, the integrity test is deemed to have a passing result.
If this value is greater than the maximum allowable value, then the test should be repeated with the permeate valve closed. This will test the system for any leaks and will help determine if the failure is due to a system leak versus a non-integral membrane. When testing the system for external leaks, the diffusive flow rate should be < 5 sccm. It may take 15 minutes or longer for the flow rate to stabilize to this point on some systems, as the permeate side of the system is relying on diffusive flow through the membrane to pressurize.
1.2 Diffusive flowrate measurement
In order to measure the diffusive flow, the useof an integrity test instrument or a flowmeter are the best ways, but in some cases if these instruments are not available, it is possible use the following procedure:
1. For a large-scale system, when maximum measurable diffusive flow ratefor theintegrity test instrument is higherthan the allowable limit, it may bepossible to perform the test using apressure decay value. This value is calculated from a formula that transforms the diffusive flowrate limit toa pressure decay limit. To obtain pressure decay limits for your assembly, please contact Pall.
2. For small, bench scale systems, when the diffusive flowrate is≤ 100 cc/min, it is possible to measure the flow manually measuring the displaced byplacing the permeate line into an inverted graduated burette in a beaker with water (refer to Figure 1). The volume of air displaced versus time will indicate the diffusive flow rate. With this method, it is a best practice to take multiple measurements in order to confirm the integrity of the system.
1.3 How to calculate the flowrate limit
The test limit should be calculated from the data in the table 1:
Example: for a 10 kDa cassette with 1.5 m2 of membrane area the calculation is the following:
1600 sccm/m2 x 1.5 m2 = 2400 sccm, where 1 sccm is a standard cubic centimeters per minute, so the final result is ≤2400 mL/min.
Test will be performed at 2.0 barg (or 30 psig) and the test limit is ≤2400 mL/min.