Capacitive Weld Defect Detection in Polyethylene Conduits
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Solution Overview
Problem
Current methods for detecting defects in polyethylene-based welds, such as those used in polyethylene conduit networks, are limited in their ability to detect smaller defects and cold fusion defects, particularly when using ultrasonic waves, which are ineffective for macroscopic defects of smaller sizes and do not account for aging or contamination issues.
Innovation Solution
A method involving the use of a capacitive probe with electrodes positioned near the weld, applying a potential difference to create an electric field that measures electrical capacitance at frequencies between 65 MHz and 1 GHz, allowing for the detection of defects as small as ten nanometers by comparing measured capacitance to a reference value, with a specific embodiment using a measurement frequency between 100MHz and 300MHz.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If ultrasonic waves are used for defect detection, then the detection method is simple and non-contact, but it cannot detect small defects or cold fusion defects
Solution Approach 1:
The patent changes the physical parameter of the detection method by switching from ultrasonic waves to electromagnetic fields at specific frequencies (65 MHz to 1 GHz). This parameter change enables the detection of small defects and cold fusion defects that are invisible to ultrasonic methods, while maintaining operational efficiency through automated capacitance measurement and comparison systems.
2Measurement precision
If capacitive probe with high measurement frequency (65 MHz to 1 GHz) is used, then small defects and cold fusion defects can be detected, but the device complexity increases
Solution Approach 1:
The patent replaces complex mechanical scanning systems with an electromagnetic field-based capacitive measurement system. By using electromagnetic fields at frequencies between 65 MHz and 1 GHz, the system achieves high-resolution defect detection without requiring mechanical contact or complex positioning mechanisms, thereby reducing overall device complexity while improving measurement precision.
3Measurement precision
If electrodes are positioned close to the weld for accurate capacitance measurement, then detection precision improves, but the risk of contamination or damage to electrodes increases
Solution Approach 1:
The patent introduces the polyethylene material itself as an intermediary between the electrodes and the weld defect. The electrodes are positioned on opposite sides of the polyethylene component, with the electric field penetrating through the material to detect defects. This intermediary arrangement allows precise capacitance measurement while protecting electrodes from direct contact with potential contaminants at the weld interface.
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 method effectively detects defects of various sizes, including those not detectable by existing technologies, providing a reliable means to assess weld quality and identify cold fusion defects, ensuring the integrity of polyethylene conduit networks.
Implementation Method 1
measuring an electrical capacitance at a measurement frequency between said first electrode and said second electrode, the measurement frequency being greater than 65 MHz and less than 1 GHz
Implementation Method 2
positioning a first electrode and a second electrode near the weld, such that at least one electric field line crosses said weld when a potential difference is applied between said first and second electrodes
Data Source
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AI summary
The invention relates to a method for detecting a defect in a weld joining a first surface of a material based on polyethylene and a second surface of a material based on polyethylene, said method comprising steps of: positioning a first electrode and a second electrode in proximity to the weld so that at least one electric field line passes through said weld when a potential difference is applied between said first and second electrodes; and measuring an electrical capacitance at a measurement frequency between said first electrode and said second electrode, the measurement frequency being higher than 65 MHz and lower than 1 GHz, in order to compare the measured electrical capacitance to a reference value.