Eddy Current Probe for Heat Exchanger Tube Ovality Detection
Find Innovative SolutionsGenerate Solutions
Solution Overview
Problem
Current non-destructive testing technologies for heat exchanger tubes in nuclear and thermoelectric power plants lack the capability to effectively detect and measure ovality of the tube's cross-sectional circumference, which can lead to accelerated corrosion and damage due to external forces or bending, resulting in undetected defects.
Innovation Solution
An apparatus utilizing a probe body with a spirally wound eddy current coil that measures the amplitude difference of signals as it moves longitudinally and rotates circumferentially within the tube, allowing for the detection of ovality by comparing signal amplitudes between multiple coil units, enabling early detection and prevention of defects.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If conventional non-destructive testing technology is used, then defect detection capability is maintained, but ovality detection capability is lost
Solution Approach 1:
The inspection system integrates multiple detection functions into a single apparatus. The probe body includes both ovality detection means (first and second detection coils arranged orthogonally) and defect detection means (third and fourth detection coils), enabling simultaneous measurement of geometric ovality and material defects during one inspection operation.
Solution Approach 2:
The detection system is divided into functionally distinct coil units: first and second detection coils for ovality measurement, and third and fourth detection coils for defect detection. This segmentation allows each subsystem to be optimized for its specific function while operating within a unified probe structure.
2Reliability
If the tube is deformed into an oval shape, then stress concentration occurs accelerating corrosion and cracks, but detection capability is insufficient
Solution Approach 1:
The patent replaces mechanical measurement methods with electromagnetic induction-based detection. The detection coils generate electromagnetic fields that interact with the tube wall, and changes in impedance caused by ovality deformation are measured electrically, providing non-contact, high-precision measurement capability.
Solution Approach 2:
The system detects ovality by measuring changes in electrical impedance parameters of the detection coils. As the tube cross-section deforms from circular to oval, the distance between the coils and tube wall varies, causing measurable changes in coil impedance that correlate with the degree of ovality.
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 predictive maintenance and fundamental prevention of damage by accurately measuring ovality during manufacturing and assembly, thereby identifying vulnerable areas and preventing cracks and corrosion.
Implementation Method 1
a spirally wound eddy current coil
Implementation Method 2
measures the amplitude difference of signals as it moves longitudinally and rotates circumferentially within the tube
Data Source
Figure 1
Figure 2~3
Figure 4~5
AI summary
Provided is an apparatus for detecting an ovality of a circumference of a cross section of a heat exchanger tube, the apparatus including a probe body inserted in a heat exchanger tube, moveable in a lengthwise direction of the heat exchanger tube, and rotatable in a circumferential direction of an inner surface of the heat exchanger tube, a support foot disposed at both ends of the probe body to support a linear movement and a rotation of the probe body, a coil support unit provided at different locations of the probe body, and an eddy current coil mounted on the coil support unit, and including a first coil unit and a second coil unit to measure an eddy current resistance to detect an ovality of the heat exchanger tube, and the eddy current coil may use one coil unit among the first coil unit and the second coil unit as a test coil and a remaining as a reference coil, or may use both the first coil unit and the second coil unit as test coils.