Air-Coupled Ultrasonic Lamb Wave Pipe Inspection
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Solution Overview
Problem
Current methods for detecting features on or within pipe walls, such as eddy currents and visual inspections, are inefficient and costly, and existing non-contact techniques like Magnetic Flux Leakage face challenges with steel pipelines due to magnetic drag and sensor fouling, while existing ultrasonic methods require high voltages and bandwidth amplifiers, limiting their effectiveness.
Innovation Solution
An air-coupled ultrasonic system using Lamb waves generated by a transmitting transducer and detected by a receiving transducer, with a narrow-band tracking filter and signal processor, allowing for non-contact detection of pipe wall features without magnets or high voltages, enabling efficient detection of defects on both inner and outer surfaces.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If eddy currents are used to detect pipe wall features, then detection capability is improved, but cost increases to approximately $1 M per 100 mile of pipe
Solution Approach 1:
The patent replaces the expensive eddy current detection system with an acoustic wave-based detection system using Lamb waves. This substitution eliminates the need for complex electromagnetic equipment and reduces inspection costs while maintaining defect detection capability through acoustic signal analysis of pipe wall conditions.
Solution Approach 2:
The invention changes the detection parameter from electromagnetic eddy currents to acoustic Lamb waves. This parameter change enables detection of pipe wall features including corrosion, cracks, and thickness variations through acoustic wave propagation characteristics, providing a cost-effective alternative to eddy current methods.
2Measurement precision
If magnets are placed close to the inner surface of the pipe for eddy current detection, then detection precision is improved, but magnetic drag increases making it difficult to move through the pipe
Solution Approach 1:
The patent replaces the magnet-based eddy current system with an acoustic transducer system that generates and detects Lamb waves. This eliminates magnetic drag forces entirely, allowing the inspection device to move freely through the pipe without resistance, while still achieving precise defect detection through acoustic wave analysis.
3Measurement precision
If magnets are placed close to the inner surface of the pipe, then detection capability is improved, but sensor elements may scrape the inner wall causing fouling
Solution Approach 1:
The invention replaces contact-based magnetic sensors with non-contact acoustic transducers that generate Lamb waves through the pipe wall. This eliminates mechanical contact between sensors and the pipe inner surface, preventing fouling and maintaining reliable operation throughout the inspection process.
4Measurement precision
If traditional ultrasonic methods are used for pipe wall detection, then detection capability is improved, but high voltages and bandwidth amplifiers are required limiting effectiveness
Solution Approach 1:
The patent changes the ultrasonic excitation method from high-voltage broadband pulses to low-voltage swept-sine wave excitation that generates specific Lamb wave modes. This parameter change simplifies the required electronics, eliminating the need for high-voltage amplifiers and complex bandwidth amplifiers, while maintaining effective pipe wall defect detection through resonant acoustic wave generation.
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
The system provides effective non-contact detection of pipe wall features with improved signal-to-noise ratio, reduced power consumption, and ability to detect defects without fouling, suitable for large-scale pipeline inspections with low maintenance and battery efficiency.
Implementation Method 1
an air-coupled transmitting transducer disposed within the hollow pipe for generating ultrasonic waves at a first chosen angle to the normal of the inner surface of the wall, at a chosen first distance therefrom
Implementation Method 2
Lamb waves are generated in the wall of the pipe; an air-coupled receiving transducer disposed within the hollow pipe at the same longitudinal position as the transmitting transducer, at a chosen angle to the inner to the normal to the inner surface of the wall
Implementation Method 3
for receiving ultrasonic waves emitted by the inner surface of the wall, the receiving transducer producing an electrical signal in response to the ultrasonic waves received thereby
Implementation Method 4
a narrow-band tracking filter for receiving the electrical signal from the receiving transducer at the excitation frequency in the selected frequency range and generating a noise-filtered signal therefrom
Data Source
AI summary
Apparatus and method for non-contact ultrasonic detection of features on or within the walls of hollow pipes are described. An air-coupled, high-power ultrasonic transducer for generating guided waves in the pipe wall, and a high-sensitivity, air-coupled transducer for detecting these waves, are disposed at a distance apart and at chosen angle with respect to the surface of the pipe, either inside of or outside of the pipe. Measurements may be made in reflection or transmission modes depending on the relative position of the transducers and the pipe. Data are taken by sweeping the frequency of the incident ultrasonic waves, using a tracking narrow-band filter to reduce detected noise, and transforming the frequency domain data into the time domain using fast Fourier transformation, if required.