Non-Volumetric Leak Detection in Underground Storage Tanks
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Solution Overview
Problem
Conventional volumetric detection methods for leaks in underground storage tanks are inadequate for detecting low-threshold leaks due to factors like temperature and pressure differences, tank deflection, and groundwater effects, which can mask actual leak indicators, failing to meet stringent regulatory standards such as the California Code of Regulations' 0.005 gallons per hour detection requirement with a 95% probability and 5% false alarm rate.
Innovation Solution
A method involving a remotely controlled device deployed into the interstitial space of a double-wall tank to visually inspect and non-volumetrically detect leaks by observing the presence of a liquid fill material, allowing direct observation of leak indicators such as drops or puddles, rather than relying on volumetric measurements, thereby increasing detection resolution and accuracy.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If conventional volumetric detection methods are used to detect leaks in underground storage tanks, then the detection system is simple and easy to operate, but the detection precision is insufficient to meet the 0.005 gallons per hour threshold requirement
Solution Approach 1:
The patent replaces the mechanical volumetric measurement system with an optical detection system. Instead of measuring liquid volume changes in a column, the system uses a camera to capture images of the liquid meniscus and analyzes these images to detect leaks. This substitution of mechanical measurement with optical measurement enables the required precision of 0.005 gallons per hour while maintaining operational simplicity through automated image analysis.
Solution Approach 2:
The patent introduces an intermediary optical measurement system between the leak source and the detection result. Rather than directly measuring volume changes, the system uses optical imaging of the liquid meniscus as an intermediary to detect and quantify leaks. This intermediary approach allows for precise measurement of extremely small leak rates that would be imperceptible in direct volumetric measurements.
2Reliability
If volumetric testing techniques are used to detect leaks, then the testing method is straightforward, but environmental factors such as temperature and pressure differences mask actual leak indicators
Solution Approach 1:
The patent replaces the mechanical volumetric measurement system with an optical detection system. Instead of measuring liquid volume changes in a column, the system uses a camera to capture images of the liquid meniscus and analyzes these images to detect leaks. This substitution of mechanical measurement with optical measurement enables the required precision of 0.005 gallons per hour while maintaining operational simplicity through automated image analysis.
Solution Approach 2:
The patent changes the measurement parameter from volumetric displacement to optical characteristics of the liquid meniscus. By measuring the position and shape of the liquid-air interface through optical imaging rather than volume changes, the system becomes insensitive to environmental factors like temperature and pressure that cause volumetric expansion or contraction, thereby improving detection reliability.
3Reliability
If conventional detection methods are used, then the system operates simply, but it cannot achieve the required 95% probability of detection with 5% false alarm rate
Solution Approach 1:
The patent replaces the mechanical volumetric measurement system with an optical detection system. Instead of measuring liquid volume changes in a column, the system uses a camera to capture images of the liquid meniscus and analyzes these images to detect leaks. This substitution of mechanical measurement with optical measurement enables the required precision of 0.005 gallons per hour while maintaining operational simplicity through automated image analysis.
Solution Approach 2:
The patent implements a feedback mechanism through automated image analysis. The system captures images of the liquid meniscus, analyzes them to detect changes indicating leaks, and can trigger alerts or further investigation. This feedback loop enables the system to achieve the required 95% probability of detection with 5% false alarm rate by continuously monitoring and comparing meniscus position over time, filtering out false positives through pattern recognition.
Data Source
AI summary
A system for the non-volumetric detection of low-threshold leaks with high resolution in underground storage tanks (USTs). A UST may be located underground with a restricted tank entry opening. The interior space of a UST may be accessed with a remotely controlled device. The presence of a liquid fill material or indicia thereof evidencing a leak may be visually observed. Variables affecting volumetric measurements of leak detection, such as temperature, pressure, tank deflection, and groundwater, may be eliminated or controlled. Visual observation may enable high resolution detection of low-threshold leaks.