MICRODYN CAPILLARY MODULES | USER MANUAL
MANN+HUMMEL Water & Fluid Solutions | REVISION DATE: 09/09/2021
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4.2
ACTIVATION WITH WATER PRESSURE
Typically, activation of the module’s membranes is required. The PP membrane is hydrophobic in nature. Liquids like water with
high surface tension of 0.072 N/m do not wet the membrane.
A simple and safe way to activate the membrane in the module(s) is the use of water at higher pressure. The first step is to fill the
module(s) bubble free with water (25 °C) from both sides (feed and permeate side). A pressure of 6 bar must be applied to the
module(s) for 1 minute. Typically, this is the tap line pressure. (Please notice the difference to the max. operating pressure given in
the data sheet.)
After this procedure, the pressure must be released to zero. The water must be exchanged, and the procedure must be repeated
four to six times. Now the module is activated and can be used for filtration.
4.3
ACTIVATION WITH WETTING AGENTS
For all filtration purposes where the module must be tested by a bubble point test for process safety reasons, the module has to be
activated by means of water-soluble liquids with a surface tension of less than 0.035 N/m.
Appropriate liquids to be used are:
•
a mixture of water and 50 vol. % of isopropanol
•
a mixture of water and 25 vol. % tert. butanol (not inflammable)
•
surfactants
With this method, it is necessary to run the module in a system for about 30 minutes in cross-flow mode until a sufficiently high
flux is reached.
After wetting, the module is flushed either with water or with the solution to be filtered to rinse any remaining agents. As long as it
stays in fluid, the membrane is activated. If the membrane dries up, it must be activated again as per the description. The
membrane’s separation properties will not change by drying.
Heavily gasifying liquids (carbonated beverages or beer) require a counter-pressure on the permeate side (e.g. 1 bar) in order to
prevent the release of gases. Gases will deactivate the membranes.
In the PBP process, a part of the permeate is pushed back by compressed gas (e.g. air). Care must be taken so that the gas is not
pressed into the membrane. Otherwise, the membranes will be made a partially hydrophobic with reduced flux. A reactivation
must then be performed.
