Filter Integrity Test Using Controlled Volume Changes
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Solution Overview
Problem
Conventional methods for testing the integrity of hydrophobic filter elements, such as those used in sterile filtration, face challenges including long measurement times, limited applicability to small filter areas, and temperature dependence, making them unsuitable for industrial-scale use.
Innovation Solution
A method and device that allow for a rapid integrity test of filter elements by maintaining a specific test pressure within a container, using controlled refilling and volume changes to determine the integrity parameter before a continuous volume flow is established, enabling testing of smaller filter areas and reducing test time to single-digit minutes.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If conventional alcohol wetting and diffusion/bubble point measurement is used, then integrity test can be performed on hydrophobic filters, but test time extends into single-digit minutes with disadvantages of after-drying and explosion-proof requirements
Solution Approach 1:
The patent changes the test medium from alcohol to RO water, fundamentally altering the testing parameters. This eliminates the need for drying steps and explosion-proof measures while maintaining test accuracy for hydrophobic PTFE filters, reducing test time significantly
Solution Approach 2:
The patent extracts and eliminates the problematic drying step from the testing process by using RO water instead of alcohol. The water flow test directly measures integrity without requiring subsequent drying, removing this time-consuming step entirely
2Ease of manufacture
If water flow test with RO water is used, then no alcohol wetting is needed and drying process is greatly reduced, but test time extends to double-digit minutes (usually 23 minutes per test object)
Solution Approach 1:
The patent applies preliminary compaction of the filter element before the actual water flow measurement. This pre-compression stabilizes the filter structure, enabling faster and more accurate measurements while maintaining the simplicity of using RO water
Solution Approach 2:
The patent introduces dynamic compaction pressure that is applied temporarily to stabilize the filter element during testing. This dynamic adjustment allows the test to proceed faster by eliminating the need for prolonged static testing periods
3Adaptability or versatility
If WFT or WFI is used for large filter areas (≥900 cm2), then integrity test can be performed, but smaller filter surfaces cannot be tested with these methods
Solution Approach 1:
The patent creates a universal testing method that works for both large and small filter areas by combining RO water flow measurement with a standardized compaction procedure. The method adapts to different filter sizes while maintaining measurement accuracy through controlled compaction pressure
4Loss of time
If indirect test methods with pressure increase/decrease measurement are used, then integrity test can be performed in single-digit minutes, but the method is temperature-dependent and requires reference volume measurement
Solution Approach 1:
The patent replaces the indirect pressure-based measurement system with a direct water flow measurement system. By measuring the actual water flow through the filter under controlled compaction, it eliminates temperature dependence and the need for reference volume measurements while maintaining fast test times
Applied Scientific Principles
This section explains which scientific principles are used to turn an abstract innovation direction into a practical engineering solution.
Function Achieved in This Case
This approach significantly reduces test time, improves measurement accuracy, and allows for the assessment of filter integrity independently of temperature, making it suitable for industrial-scale applications and smaller filter elements.
Implementation Method 1
the fluid only leaves the container after the fluid has penetrated the filter element, e.g. through evaporation
Data Source
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AI summary
A method for carrying out an integrity test on a filter element has the steps: filling at least one vessel (1), in which a filter element (F) to be tested is arranged, with a fluid, – setting the pressure of the fluid in the vessel (1) to a predetermined specific test pressure, maintaining the specific test pressure in the vessel (1) with controlled replenishment of fluid into the vessel (1) and/or with a controlled change in internal volume of the vessel (1), – determining an integrity characteristic variable for the filter element (F) in a manner dependent on the controlled replenishment of fluid into the vessel (1) and/or in a manner dependent on the controlled change in internal volume of the vessel (1) before a substantially continuous volume flow of fluid, which is required for maintaining the specific test pressure in the vessel (1), arises. A corresponding device for carrying out an integrity test on a filter element is also proposed.