Rotatable Eddy Current Probe for Steam Generator Tube Weld Inspection
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Solution Overview
Problem
Current inspection methods for heat-transfer-tube sealing portions in steam generators, such as permeation tests and radiation tests, are inefficient in detecting internal defects like blowholes and require extensive time for thorough examination, while eddy-current flaw detection methods struggle to maintain a consistent gap and cover the entire area effectively.
Innovation Solution
An inspection device with a rotatable main unit and multiple probes that can be pressed against the welded portions by elastic members, allowing for circumferential and radial movement to detect defects efficiently and accurately, while minimizing disturbance noise through dual rotation and non-overlapping inspection areas.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If radiation test (RT) is used to detect internal defects, then detection capability for internal defects is improved, but inspection speed deteriorates
Solution Approach 1:
The inspection system segments the inspection task by using multiple ECT coils arranged at different positions and orientations. Each coil inspects a specific region or aspect of the welded portion, allowing parallel inspection of multiple areas simultaneously, thereby improving overall inspection speed while maintaining defect detection capability
Solution Approach 2:
The invention transitions from single-point inspection to multi-dimensional inspection by arranging ECT coils in three-dimensional space around the welded portion. This spatial arrangement enables comprehensive coverage of the inspection area from multiple angles and depths, achieving both rapid inspection and thorough defect detection
2Measurement precision
If ECT coil is moved to follow surface asperities, then detection accuracy is improved, but device complexity increases
Solution Approach 1:
The invention uses a flexible pressing mechanism with elastic members that allow the ECT coils to conform to surface asperities passively. The elastic pressing force enables the coils to adapt to surface irregularities without requiring complex active positioning systems, maintaining detection accuracy while simplifying the overall device structure
Solution Approach 2:
The ECT coils are designed to self-adjust to the surface geometry through elastic pressing. The system uses the surface profile itself to guide the coil positioning, eliminating the need for external complex positioning mechanisms. The coil naturally follows the surface contours under elastic force, achieving accurate tracking autonomously
3Area of stationary object
If ECT coil area is increased to cover more area, then inspection coverage is improved, but inspection speed deteriorates
Solution Approach 1:
The inspection system divides the total inspection area into multiple zones, each covered by a dedicated ECT coil. Multiple coils operate simultaneously to inspect different regions, achieving comprehensive coverage without requiring a single large coil that would move slowly. This parallel inspection approach maintains high speed while covering the entire welded portion area
Solution Approach 2:
The invention merges the inspection capabilities of multiple ECT coils arranged in an array to achieve both wide coverage and rapid inspection. By combining the output signals from multiple coils and coordinating their simultaneous operation, the system achieves the equivalent of a large inspection area while maintaining the speed advantage of smaller, faster-moving coils
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 rapid and precise inspection of all heat-transfer-tube sealing portions in a steam generator, allowing for defect detection and shape analysis, reducing inspection time and improving accuracy by maintaining consistent probe distances and minimizing noise interference.
Implementation Method 1
ECT is a method in which a high-frequency eddy current is made to flow at a surface of an inspection target
Implementation Method 2
impediment to the flow of the eddy current and phase changes thereof due to a defect are detected as changes in electromagnetic induction
Implementation Method 3
a pressing portion that presses the probe toward the welded portion
Data Source
AI summary
An inspection device that is capable of inspecting all heat-transfer-tube sealing portions in a steam generator and that is also capable of analyzing a defect shape is provided. An inspection device that employs the eddy-current flaw detection method to inspect the presence/absence of a defect in a welded portion (103) between a tube (101) and a tube plate (102) is provided with a main unit (41) that has a circular-column portion (41A), which is inserted into the tube (101), and a flange portion (41B), which is pressed against the tube plate (102), and that is rotatable with respect to the welded portion (103); a probe (42) that is disposed inside the main unit (41), that can be moved close to and away from the welded portion (103), and that detects a defect in the welded portion (103); and a pressing portion (44) that presses the probe (42) toward the welded portion.