US-12623189-B2 - Process for testing filters

US12623189B2US 12623189 B2US12623189 B2US 12623189B2US-12623189-B2

Abstract

The present disclosure relates to a process for testing the integrity of membranes in a filter module. Specifically, the process is applied to filters for extracorporeal blood treatment, in particular, filters comprising both filter membranes and particulate material.

Inventors

Claudia ASSMANN
Ralf Flieg
Wolfgang Freudemann
Torsten KNOER
Mehmet Yildirim

Assignees

GAMBRO LUNDIA AB

Dates

Publication Date: 20260512
Application Date: 20180815
Priority Date: 20170816

Claims (19)

1 . A process for identifying damage to a filter comprising a first compartment and a second compartment, wherein the first compartment and the second compartment are separated by a porous membrane, said process comprising the steps of: i) providing the filter, wherein the first compartment of the filter and the second compartment of the filter are both filled with a testing liquid; ii) establishing a pressure gradient between the first compartment and the second compartment by introducing a testing gas into the first compartment, thus displacing the testing liquid from the first compartment; iii) evaluating the filter via a) monitoring the pressure gradient established in step ii), b) measuring flow of the testing gas through the porous membrane separating the first compartment and the second compartment, or c) both; wherein the testing liquid is an aqueous solution of sodium chloride comprising a salt concentration in the range of from about 10 wt. % to about 20 wt. %; and wherein the testing gas is air.
2 . The process of claim 1 , wherein the first compartment of the filter comprises particulate matter selected from polymer beads and particles comprising activated carbon or the second compartment of the filter comprises particulate matter selected from polymer beads and particles comprising activated carbon.
3 . The process of claim 2 , wherein the first compartment of the filter comprises polymer beads or the second compartment of the filter comprises polymer beads.
4 . The process of claim 1 , wherein the porous membrane is a bundle of hollow fiber membranes.
5 . The process of claim 2 , wherein the porous membrane is a bundle of hollow fiber membranes.
6 . The process of claim 3 , wherein the porous membrane is a bundle of hollow fiber membranes.
7 . The process of claim 1 , wherein the first compartment of the filter comprises particulate matter.
8 . The process of claim 1 , wherein the second compartment of the filter comprises particulate matter.
9 . The process of claim 1 , wherein the porous membrane comprises one or more polymers selected from the group consisting of polysulfones, polyethersulfones, polyacrylonitrile, polytetrafluoroethylene, polyvinylidene fluoride, polyvinylpyrrolidone, polyetherimine ethylene vinyl acetate, and any combination thereof.
10 . A process for identifying damage to a filter comprising a first compartment and a second compartment, wherein the first compartment and the second compartment are separated by a porous membrane, said process comprising the steps of: i) providing the filter, wherein the first compartment of the filter and the second compartment of the filter are both filled with a testing liquid; ii) establishing a pressure gradient between the first compartment and the second compartment by introducing a testing gas into the first compartment, thus displacing the testing liquid from the first compartment; iii) evaluating the filter via a) monitoring the pressure gradient established in step ii), b) measuring flow of the testing gas through the porous membrane separating the first compartment and the second compartment, or c) both; wherein the testing liquid is an aqueous solution of sodium chloride comprising a salt concentration of about 10 wt. %; and wherein the testing gas is air.
11 . The process of claim 10 , wherein the first compartment of the filter comprises particulate matter selected from polymer beads and particles comprising activated carbon or the second compartment of the filter comprises particulate matter selected from polymer beads and particles comprising activated carbon.
12 . The process of claim 11 , wherein the first compartment of the filter comprises polymer beads or the second compartment of the filter comprises polymer beads.
13 . The process of claim 10 , wherein the porous membrane is a bundle of hollow fiber membranes.
14 . The process of claim 10 , wherein the porous membrane comprises one or more polymers selected from the group consisting of polysulfones, polyethersulfones, polyacrylonitrile, polytetrafluoroethylene, polyvinylidene fluoride, polyvinylpyrrolidone, polyetherimine ethylene vinyl acetate, and any combination thereof.
15 . A process for identifying damage to a filter comprising a first compartment and a second compartment, wherein the first compartment and the second compartment are separated by a porous membrane, said process comprising the steps of: i) providing the filter, wherein the first compartment of the filter and the second compartment of the filter are both filled with a testing liquid; ii) establishing a pressure gradient between the first compartment and the second compartment by introducing a testing gas into the first compartment, thus displacing the testing liquid from the first compartment; iii) evaluating the filter via a) monitoring the pressure gradient established in step ii), b) measuring flow of the testing gas through the porous membrane separating the first compartment and the second compartment, or c) both; wherein the testing liquid is an aqueous solution of sodium chloride comprising a salt concentration of about 20 wt. %; and wherein the testing gas is air.
16 . The process of claim 15 , wherein the first compartment of the filter comprises particulate matter selected from polymer beads and particles comprising activated carbon or the second compartment of the filter comprises particulate matter selected from polymer beads and particles comprising activated carbon.
17 . The process of claim 16 , wherein the first compartment of the filter comprises polymer beads or the second compartment of the filter comprises polymer beads.
18 . The process of claim 15 , wherein the porous membrane is a bundle of hollow fiber membranes.
19 . The process of claim 15 , wherein the porous membrane comprises one or more polymers selected from the group consisting of polysulfones, polyethersulfones, polyacrylonitrile, polytetrafluoroethylene, polyvinylidene fluoride, polyvinylpyrrolidone, polyetherimine ethylene vinyl acetate, and any combination thereof.

Description

CROSS-REFERENCE TO RELATED APPLICATIONS This application is the U.S. national phase of PCT/EP2018/072092, filed on Aug. 15, 2018, which claims the benefit of European Patent Application Serial Number 17186479.6, filed on Aug. 16, 2017, the entire disclosures of both of which are incorporated herein by reference. TECHNICAL FIELD The present disclosure relates to a process for testing the integrity of membranes in a filter module. Specifically, the process is applied to filters for extracorporeal blood treatment, in particular, filters comprising both filter membranes and particulate material. DESCRIPTION OF THE RELATED ART Diffusion and/or filtration devices comprising hollow fiber membranes are used in various medical treatments which remove unwanted substances from body fluids, e.g., blood. Examples of such treatments are hemodialysis, hemodiafiltration and hemofiltration. Membrane filters are also used in the production of sterile liquids, by causing the liquid to pass through a semi-permeable membrane able to filter the germs. Various processes for checking the integrity of a filter have been described. One of the known processes is the bubble point test (BPT), which can check on the absence of membrane pores having pores which have a greater size than a predetermined limit. The BPT considers the membrane pores as capillary tubes, and the maximum radius of the pores is determined by pressure measurements. The test briefly comprises the following stages: the membrane is wetted so that the pores are full of liquid; a first side of the membrane is connected to a gas source, while the opposite side is connected to a liquid for easy detection of gas bubbles; the first side of the membrane is gradually pressurized with the gas; while the gas pressure on the first side remains relatively low, a modest amount of gas will displace, by diffusion, through the liquid contained in the membrane pores towards the second side of the membrane; this amount of gas flow is proportional to the speed of increase of gas pressure on the first side; when the gas pressure reaches a certain level, the liquid contained in the largest pores is forced to exit from the pores themselves, and a considerable amount of gas crosses the largest pores, reaching the liquid connected to the second side of the membrane, forming gas bubbles within the liquid; in this situation a further pressuring action leads to a further displacement of gas towards the second side of the membrane, with no discernible increase in pressure; the substantially stable pressure reached in this situation (bubble point pressure, or BP pressure) is a known function of the maximum radius of the membrane pores and thus enables determination thereof; stopping the pressurization action leads to a situation of substantial equilibrium in the BP pressure. U.S. Pat. No. 5,064,529 A describes an automatic BPT (without the need to observe the moment of gas bubble formation) to check whether the effective BP pressure of the membrane corresponds to the desired BP pressure corresponding to the maximum diameter of the pores indicated by the membrane manufacturer; in a first stage the first side of the membrane is pressurized with the gas at a predetermined constant pressurization speed, at the end of which first stage the pressure measured on the first side of the membrane should correspond to a predetermined theoretical pressure; the pressurization speed and the pressurization time are chosen so that the above-mentioned theoretical pressure is lower than the desired BP pressure; if the pressure measured after the predetermined time does not correspond to the theoretical pressure, a fault is signaled due, probably, to the breakage of the membrane or a faulty installation of the filter; in a second stage, the pressurization is halted for a certain time period in which the pressure should remain substantially constant; if, on the contrary, there is a significant drop in pressure, a fault is signaled due, probably, to the faulty filling-up of the pores with the liquid; in a third stage, the pressurization of the first side of the membrane is re-established at a predetermined speed for a predetermined time, during which theoretically the desired BP pressure is reached; if, at the end of the third stage, the desired BP pressure is measured, within a predetermined range of acceptability, it is considered that the maximum diameter of the pores is the desired one. U.S. Pat. No. 5,594,161 A describes a process for testing the integrity of one or more filtering elements in which the inlet side of the filter element is wetted and subjected to a gas pressure which is kept constant, while the pressure is measured on the outlet side which, previously, has been made part of a closed system. If, after a predetermined time, the outlet pressure does not exceed a predetermined threshold value, the filter element is considered intact. U.S. Pat. No. 4,614,109 A describes a process for checking the perme