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15 Start up of cassettes
5.5 Determining Clean Water Flux for Filter Cassettes (CWF)
The water flux test is an easy and non-destructive test that measures the ability of
water to pass through the membrane in a specific system setup. Residuals on the
membrane surface will impact water flux rates. Determining the water flux rate
enables the user to confirm the ability of a cleaning cycle to restore filtration rate of
the system. The water flux should be trended over time and evaluated for potential
membrane and system changes.
It cannot be used to assess the removal of preservative, cleaning or process residue.
Specific analytical techniques are required to quantify residues.
Determine a clean water flux
Proceed as follows:
t
Rinse new installed cassettes to remove preservatives.
t
Post use sanitization cassettes with 1 N Sodium hydroxide and neutralize.
t
Run the clean water flux with purified water as specified in the table below.
t
Measure retentate rate and permeate rate at constant temperature (20°C).
t
Trend the clean water flux and water flux determined after cleaning to detect
membrane and system changes. The clean water flux is used as the base line value.
Any changes in water quality, applied pressure, temperature and viscosity,
system design and membrane, will have an effect on the water flux.
In systems containing more than one Sartocon ® or a Sartocube ® , the interpretation can
be simplified by establishing a baseline for a given set of devices in a given system.
Flow path restriction may not allow performing the flux test with the above-
mentioned parameters. In that case a different test pressure should be used to
perform a water flux test. Once the parameters are defined they have to remain
constant during every test to assure comparability.
System Pressure Examples for Water Flux Determination:
Cassette Design Feed Pressure
valve open
[psi|bar|kPa]
Retentate
Pressure
[psi|bar|kPa]
Permeate Pressure
valve open
[psi|bar|kPa]
Sartocon
®
Slice
Cassette and
Slice 200
29|2|200 7|0.5|50 0|0|0
Sartocon
®
Cassette 29|2|200 7|0.5|50 0|0|0
Multiple Sartocon
®
Cassettes
29|2|200 10–14|0.7–1|70–100
<
7|0.5|50
Sartocube
®
Cassette 29|2|200 10–14|0.7–1|70–100
<
7|0.5|50
Although the flux rate of used filter cassettes will normally not be fully regained,
the flux rate after use and cleaning should approximate the clean water flux.
Trending the water flux helps to evaluate the cleaning status of the system.
Cleaning optimization should be considered:
− If the permeate flux rate is below 70% of the clean water flux.
− If the permeate flux rate decreases from run to run.
In case of further questions please contact our Sartorius Stedim application specialist.