Membrane Filter Diffusion Testing With Statistical Noise Cutoffs
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Solution Overview
Problem
Existing gas-liquid diffusion integrity tests for membrane filters suffer from high background noise variability due to differences in membrane properties, equipment, and operating conditions, leading to reduced sensitivity in defect detection and increased false failures.
Innovation Solution
A method that normalizes gas-liquid diffusion data by equipment test position and cast date to reduce background noise, using a two-cutoff system with an initial fixed cutoff and a secondary statistical cutoff based on normalized data to improve signal-to-noise ratio and detect defects as small as 5 microns.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If traditional gas-liquid diffusion integrity tests are used, then the test can be performed with simple equipment and procedures, but the background noise variability is high which reduces defect detection sensitivity
Solution Approach 1:
The patent applies preliminary action by performing normalization of diffusion data based on cast date and bowl position before conducting the defect detection analysis. This pre-processing step establishes baseline corrections that reduce background noise variability, allowing the subsequent defect detection to operate on normalized data with reduced noise, thereby improving sensitivity without adding complex hardware
Solution Approach 2:
The patent introduces statistical normalization factors as intermediary elements between the raw diffusion measurements and the defect detection decision. These normalization factors act as mediators that account for systematic variations due to cast date and bowl position, effectively filtering out background noise while preserving defect signals
2Reliability
If the acceptable specification window is expanded to accommodate noise variability, then false failures are reduced, but the defect detection capability decreases
Solution Approach 1:
The patent changes the parameter space by transforming raw diffusion measurements into normalized diffusion values through division by normalization factors. This parameter transformation effectively rescales the data to account for systematic variations, allowing for tighter specification windows that maintain high defect detection capability while reducing false failures, as the normalized data has reduced variability
3Measurement precision
If normalization by cast date and bowl position is applied, then background noise is reduced and signal-to-noise ratio improves, but the data processing complexity increases
Solution Approach 1:
The patent applies parameter changes by transforming the raw diffusion measurement parameter into a normalized parameter that accounts for cast date and bowl position effects. This mathematical transformation (division by normalization factors) effectively separates the defect signal from background noise, improving signal-to-noise ratio while maintaining relatively simple processing that can be implemented through standard computational methods
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
Enhances defect detection capability, reduces false failures, and maintains yield by minimizing the impact of noise variability, allowing for more stringent and consistent product disposition without sacrificing sensitivity.
Implementation Method 1
gas molecules migrate through water-filled pores of a wetted membrane in accordance with Fick's Law of Diffusion
Implementation Method 2
High purity filtration of aqueous media used in the fields of biotechnology, chemistry, electronics, pharmaceuticals, and the food and beverage industries are obtained the use of sophisticated membrane filter modules capable of a high degree of separation
Data Source
AI summary
The disclosure herein relates to a method of reducing background noise during integrity testing of membrane filter to increase sensitivity and more effectively disposition failing membrane filters.