6.3 Stage 2 – Measuring water flux
Measuring water flux involves measuring the flow of water through the cassette’s membrane under
controlled conditions. You convert the measurement into units that represent water flux. The water
flux value you obtain provides an indicator of the performance of the cassette.
Cytiva recommends that you measure water flux when the cassette is new and before each use. By
tracking the water flux measurements, you can; (1) determine the effectiveness of cleaning cycles,
and (2) determine when a cassette reaches the end of its service life.
Measuring water flux manually requires about 30 minutes and this equipment: graduated cylinder,
stopwatch, thermometer, calculator, pen and paper. If you have a flow meter installed on the
permeate line, you can use the flow meter for measuring flux.
Summary of water flux measurement procedure
The following steps summarize how to measure water flux:
Step
Action
1
Measure the water flow from the permeate port at two transmembrane pressures.
2
Calculate water flux in l/m
2
/hr (LMH) for the two water flow measurements.
3
Plot the two flux values. Then interpolate Kvick Lab cassette water flux at 0.7 barg (10
psig) transmembrane pressure.
4
Normalize the water flux value to 20 °C and 1 psig to arrive at flux in LMH/psig @ 20 °C.
5
Record the flux value as a benchmark for future comparison. Compare the flux with
previously obtained values.
The following text describes how to complete each step.
Measure flow from the permeate port
Follow these steps to measure the water flow rate from the permeate port:
Step
Action
1
Rinse the cassette following the instructions in
Section 6.2 Stage 1 – Rinse storage
solution from the cassette, on page 28
2
Setup your cross-flow system to circulate the retentate and permeate back to the feed
reservoir (
).
3
Fill the feed reservoir with a volume of deionized water or WFI. Fully open the feed,
retentate, and permeate valves.
6 Preparing a Cassette for Use
6.3 Stage 2 – Measuring water flux
30
Learning to Use the Kvick Lab Cassette Holder User Manual 18117269 AI
