Method for conducting an integrity test of filter elements
A method is made available for conducting an integrity test of filter elements ( 3 ), in particular of sterile filters. The integrity test involves direct measurement, at constant pressure, of a liquid flow on the inflow side of the filter element ( 3 ) to be tested. The test method is practically independent of changing environmental conditions, provides a result which is not distorted by a change of pressure on the inflow side of the filter element, and permits a very short measurement time.
1. A method for conducting an integrity test of filter elements, comprising the steps of:
setting up a measurement arrangement comprising at least one container, which has a filter housing with an inlet and an outlet for a fluid and, arranged between these and separating them, at least one filter element, which is a hydropholic membrane filter, the container on the inflow side being connected via pressure-resistant lines to a flow meter cell for a liquid aqueous medium, to a pressure-resistant feed tank, to a pressure-regulating station for a gaseous medium, to a compressed gas source and, if appropriate, to an intermediate container;
wherein the container, in the top part on the inflow side, has a line with an air relief or shut-off valve, and, in the bottom part, is connected to the flow meter cell, to the pressure-resistant feed tank, to the pressure-regulating station, and to the compressed gas source;
the pressurized liquid aqueous medium from the feed tank is introduced through the flow meter cell and into the inflow space of the container until the whole inflow space is filled with the liquid aqueous medium, whereupon the shut-off valve at the top of the container is closed;
thereafter the gas pressure in the system is increased by an operating pressure which is sufficient to ensure that the liquid aqueous medium begins to penetrate into the pores of the hydrophobic filter element;
the total pressure made up of geostatic pressure and operating pressure is maintained constant;
the flow of the liquid aqueous medium through the flow meter cell is measured at the constant total pressure in a stabilization phase until a constant flow through the flow meter cell is established;
after completion of the stabilization phase, the flow of the liquid aqueous medium through the flow meter cell in a measurement phase is measured at constant pressure and recorded; and
the flow value obtained is compared with the flow value indicated or determined for the integral filter element.
2. The method as claimed in claim 1 , in which the hydrophobic membrane filter is a microporous membrane filter.
3. The method as claimed in claim 2 , in which the microporous membrane filter is a sterile filter.
4. The method as claimed in claim 1 , in which the measurement arrangement comprises more than one container.
5. The method as claimed in claim 4 , in which each container has more than one filter element.