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27
Figure 19
System Setup for Flushing
Procedure
1. Refill feed tank with water (or attach feed line to water supply).
2. Open the retentate and permeate valve.
3. Adjust the pump to deliver a flow rate of 5 to 10 L/min/m
2
(0.5 to 1 L/min/ft
2
).
Do not exceed a feed pressure of 2 barg (30 psig).
4. Adjust the retentate valve to split flow 25% retentate, 75% permeate.
5. Readjust pump to give required retentate flow rate.
6. Pass 40 L/m
2
(4 L/ft
2
) to waste.
7. Stop the pump.
The effectiveness of this flushing protocol to reduce or eliminate TOC will depend on
the nature and level of the extractables and minimum acceptable levels. The user
must evaluate and validate the effectiveness of the process with respect to time,
temperature and other operating conditions.
4.5
Determine Normalized Water Permeability (NWP
20 °C
) for Cassettes
The initial NWP
20 °C
of the membrane cassette is essential to calculate because it is used as the
basis for determining membrane recovery (i.e., how effectively the membrane was cleaned back
to its original state).
This procedure must be performed with all new cassettes after steps 4.2 through 4.4 are
completed.
Water quality should be Water for Injection (WFI) or minimally 0.2 µm filtered DI water.
All calculated water permeability rates are normalized to a temperature of 20 °C by applying a
temperature correction factor (TCF
20 °C
) given in Table 11.
The procedure recommended for performing NWP is with the retentate valve closed (Dead-end
Method). This will apply a uniform pressure across the pathlength of the cassette.
The initial NWP should be measured on the new cassette after sanitization/flushing
(Section 4.3). The NWP should again be determined after cleaning and flushing (Section 5.3),
and before and after each use. An example for determining NWP is shown in Section 4.5.4.
Note: If the cleaning protocol for the process uses harsher conditions (such as higher
concentration, higher temperature, or a different cleaning agent) than the sanitization
procedure, then it is recommended that a full cleaning protocol and flushing be performed prior
to performing the initial NWP
20 °C
.
Retentate
Permeate
Feed
Tank
Waste
Waste
Feed
Pump
Pp
Rp
Fp
