Eddy-current testing uses electromagnetic induction to detect flaws in conductive materials. There are several limitations, among them: only conductive materials can be tested, the surface of the material must be accessible, the finish of the material may cause bad readings, the depth of penetration into the material is limited by the materials' conductivity, and flaws that lie parallel to the probe may be undetectable.
In a standard eddy current testing a circular coil carrying current is placed in proximity to the test specimen (which must be electrically conductive).The alternating current in the coil generates changing magnetic field which interacts with test specimen and generates eddy current. Variations in the phase and magnitude of these eddy currents can be monitored using a second 'receiver' coil, or by measuring changes to the current flowing in the primary 'excitation' coil. Variations in the electrical conductivity or magnetic permeability of the test object, or the presence of any flaws, will cause a change in eddy current and a corresponding change in the phase and amplitude of the measured current. This is the basis of standard (flat coil) eddy current inspection, the most widely used eddy current technique.
However, eddy-current testing can detect very small cracks in or near the surface of the material, the surfaces need minimal preparation, and physically complex geometries can be investigated. It is also useful for making electrical conductivity and coating thickness measurements.
We can provide Eddy Current Testing (UT) training courses and examinations suitable for the following certification schemes at Level 1 & 2.
SNT-TC-1A, CP 189 in accordance with your company written practice
If a candidate wishes to go direct to Level 2 without first taking the Level 1 route, the minimum requirements are the total accumulative requirements of both Level 1 and 2.
We can also provide Preparation training for ASNT Level 3
NDT Academy can tailor make the syllabus to satisfy the requirements of an individual’s company specific written practice if requested.
Eddy Current Testing Level II Topical Outline
1.0 Review of Electromagnetic Theory
2.0 Factors That Affect Coil Impedance
(Test part, Conductivity, Permeability, Mass, Homogeneity, Test system, Frequency, Coupling, Field strength, Test coil and shape, Hall elements)
3.0 Signal-to-Noise Ratio
4.0 Selection of Test Frequency
5.0 Coupling (Fill factor, Lift-off)
6.0 Field Strength and Its Selection
7.0 Instrument Design Considerations
(Single & Multi Frequency, Amplification, Phase detection, Differentiation of filtering)
8.0 Explanation of Standards and Specifications used in Eddy Current Testing.
9.0 Calibration and Acceptance Standard.
10.0 Practical Application & Training
10.1 Surface & Near Surface Flaw Detection
10.2 Plating & Coating
10.3. Cladding & Wall Thickness
10.4 Hardness & Heat Treatment
10.4 Tube Inspection
(Standard reference comparisons, History of part, Probability of type of discontinuity, Degrees of operator discrimination, Effects of ultrasonic frequency, Damping effects)