21
Start up of cassettes
5.7 Filtration
A critical time during crossflow filtration is at start up. The process fluid to be filtered
initially contacts the clean membrane surface. Until the desired steady state process-
ing conditions are attained, a higher than expected permeate flux rate will prevail.
This is especially true for microfiltration.
Please consider:
− Partly close permeate valve to limit permeate flow.
Starting a Crossflow filtration process:
t
Prime the permeate and retentate areas with one of the liquids listed below:
− Isotonic physiological saline
− Processing buffer
To prime the system using one of the liquids listed above, follow the directions given
in [
Æ
Chapter “5.3 Rinsing Cassettes”, page 13].
t
Reduce permeate outlet valves setting to allow a small amount of fluid to exit.
t
Generate the desired crossflow rate.
t
Open the permeate outlet valve until the desired TMP is attained.
t
Make sure that the desired crossflow rate is maintained during the compete
process.
t
Reset the desired process TMP if required.
The pressure at the feed inlet pinlet must not exceed 58 psi|4 bar.
The maximum allowable backpressure for all cassettes is: < 14 psi|1.0 bar|
100 kPa. Except for Hydrosart
®
UF.
During filtration, the crossflow rate should be held constant.
Viscosity increase during filtration will increase the inlet pressure.
t
At the end of filtration, flush the system [
Æ
Chapter “5.3 Rinsing Cassettes”,
t
After flushing, clean the system [
Æ