Dry-State Aerosol Testing for Small Filter Defect Detection
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Solution Overview
Problem
Existing methods for integrity testing of liquid sterilizing grade filters are time-consuming, require wetting the filter, and lack sensitivity to detect defects smaller than 20 µm, which can compromise retention performance.
Innovation Solution
An aerosol integrity test method that detects defects as small as 2 µm in diameter without wetting the filter, using an aerosol particle stream to challenge the filter and detect particles penetrating defective regions, with optimized parameters for concentration, pressure, and duration.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If traditional diffusion or pressure hold tests are used, then filter integrity can be tested, but the filter must be wetted which consumes time and water
Solution Approach 1:
The patent changes the physical state parameter of the test medium from liquid (requiring wetting) to aerosol (gas-phase particles), allowing integrity testing without the filter wetting step. This parameter change eliminates the time and water consumption associated with traditional diffusion tests while maintaining the ability to detect filter defects.
Solution Approach 2:
The patent uses aerosol (gas-phase particle stream) instead of liquid to challenge the filter. By employing pneumatic delivery of aerosol particles, the test eliminates the hydraulic wetting step required by traditional methods, achieving faster testing without compromising integrity assessment.
2Reliability
If traditional diffusion or pressure hold tests are used, then filter integrity can be tested, but sensitivity is limited by background noise
Solution Approach 1:
The patent changes the test medium from liquid diffusion to aerosol particle penetration, fundamentally altering the measurement parameters. This change eliminates background noise inherent in liquid-based tests, as aerosol particles provide a cleaner signal for detecting filter defects, thereby improving measurement precision and defect detection sensitivity.
Solution Approach 2:
The patent replaces the mechanical/liquid diffusion-based testing system with an aerosol particle penetration system. This substitution eliminates the background noise problems associated with liquid diffusion tests, enabling more precise detection of small defects through particle counting methods.
3Productivity
If aerosol testing is used for liquid filters, then testing speed improves and wetting is eliminated, but particle capture mechanisms in gases may not reflect liquid filtration performance
Solution Approach 1:
The patent carefully selects aerosol particle size parameters to match the liquid pore size rating of the filter (e.g., using 0.2 µm aerosol particles for 0.2 µm rated filters). This parameter matching ensures that aerosol particle penetration behavior reliably indicates liquid retention performance, resolving the concern about mechanism differences between gas and liquid phases.
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
Enables non-destructive, high-sensitivity detection of small defects in liquid sterilizing grade filters, achieving faster testing times and improved defect detection sensitivity compared to conventional methods.
Implementation Method 1
generating an aerosol particle stream wherein the particles in the stream have a suitable size and a suitable concentration to challenge the filter and penetrate a defective region in the filter without penetrating integral regions in the filter
Implementation Method 2
detecting particles that penetrate the defective region. Because an integral filter will not exhibit any particle passage, the detection of only a single or a few particles indicates a defect.
Data Source
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AI summary
A method of aerosol integrity testing of filters, capable of detecting single defects that are less than 20 um in diameter, and even as small as 2 um in diameter, in liquid sterilizing grade filters such as filter cartridges. The method challenges the filter in a dry state with a particle stream of aerosol particles of the appropriate size and in the appropriate concentration, such that at least one or more of the particles in the stream will penetrate a defective region or regions within the membrane but will not penetrate in the integral region of the membrane. Wetting of the filter is not required.