Partial Saturation Eddy Current Testing Using Movable Permanent Magnets
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Solution Overview
Problem
Current non-destructive testing techniques for tubular components in the oil and gas industry face challenges such as the need for good acoustic coupling, sensitivity to dirt and debris, limitations in material type, depth of penetration, and logistical issues in remote environments, particularly when inspecting flexible risers with multi-layer designs.
Innovation Solution
An inspection tool with movably mounted permanent magnets generating a variable DC magnetic field, combined with eddy current probes and integrated magnetic field sensors, allows for accurate and reproducible partial saturation eddy current testing, reducing the need for heavy electromagnets and enabling in-situ testing of electrically conductive components, including flexible risers.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Temperature
If heavy electromagnets are used to generate DC magnetic field for eddy current testing, then the magnetic field strength is sufficient for saturation testing, but the device weight increases and deployment in remote environments becomes difficult
Solution Approach 1:
The patent replaces the mechanical/electrical electromagnet system with a permanent magnet system. The permanent magnet provides the necessary DC magnetic field without requiring heavy electromagnetic coils and power supplies, thereby reducing the overall weight of the inspection tool while maintaining sufficient magnetic field strength for saturation testing.
Solution Approach 2:
The patent introduces a movable permanent magnet that can be positioned at different locations within the inspection tool. This allows the magnetic field strength to be dynamically adjusted by changing the magnet's position relative to the test component, enabling flexible control of the DC magnetic field without requiring a heavy, fixed electromagnet system.
2Measurement precision
If conventional eddy current testing is performed without DC magnetic field bias, then the equipment is simpler, but the depth of penetration and detection capability are limited
Solution Approach 1:
The patent combines conventional eddy current testing with DC magnetic field biasing in a single integrated inspection tool. The permanent magnet provides the DC bias field while the eddy current probe performs the actual testing, merging two techniques into one system that achieves deeper penetration and improved defect detection without requiring separate testing equipment.
Solution Approach 2:
The inspection tool is designed to perform multiple functions: generating DC magnetic field, inducing eddy currents, and detecting defects. This multi-functional approach allows the system to achieve both saturation testing capability and conventional eddy current testing in one device, improving detection capability without proportionally increasing complexity.
3Measurement precision
If ultrasonic inspection is performed with good acoustic coupling, then the wall thickness measurement is accurate, but the requirement for couplant and sensitivity to dirt/debris increases operational complexity
Solution Approach 1:
The patent replaces the ultrasonic acoustic coupling system with an electromagnetic-based eddy current testing system. This substitution eliminates the need for liquid or gel couplants and removes sensitivity to dirt and debris on the test surface, thereby improving ease of operation in field conditions while maintaining measurement capability through the DC-biased eddy current method.
4Reliability
If MFL testing is performed with high level magnetization, then the signal repeatability is good, but the equipment complexity and power requirements increase
Solution Approach 1:
The patent replaces the complex electromagnet-based magnetization system with a permanent magnet system. The permanent magnet provides stable, repeatable DC magnetic field without requiring complex control circuits, power supplies, or adjustment mechanisms, thereby achieving good signal repeatability with reduced device complexity and lower power requirements.
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 solution provides a lightweight, efficient, and accurate method for non-destructive testing of tubular components, capable of detecting defects within multiple layers of flexible risers, reducing false readings and eliminating the need for additional testing techniques, while being suitable for remote and sub-sea deployments.
Implementation Method 1
a magnetizer unit having a movably mounted permanent magnet suitable for generating a variable DC magnetic field within the test component
Implementation Method 2
ECT is based on the principle of measuring the absolute or relative impedance Z of a probe or sensor that comprises a conducting coil to which an alternating current is applied. When the alternating current is applied to the probe a magnetic field develops in and around the coil. This magnetic field expands as the alternating current rises to a maximum and collapses as the current is reduced to zero. If another electrical conductor (the apparatus to be tested) is brought into close proximity to this changing magnetic field, electromagnetic induction takes place and eddy currents (swirling or closed loops of currents that exist in metallic materials) are induced within the apparatus to be tested.
Implementation Method 3
The eddy currents flowing in the test material generate their own secondary magnetic fields which oppose the primary magnetic field of the coil and thus change the impedance detected by the probe.
Data Source
AI summary
A method for the non-destructive testing of a test component made of an electrically conductive material is described. The method employs movably mounted permanent magnets, which provides a means for generating a variable DC magnetic field within the test component, and eddy current probes to provide a means for performing a partial saturation eddy current test upon the test component. The eddy current probe preferably comprises an integrated magnetic field sensor which increases the accuracy and flexibility of the modes of operation of the described methods. The described methods are particularly suited for the inspection of tubular components that are often remotely located within the oil and gas exploration and production industries.