Eddy Current Test (ET)
Eddy current test uses electromagnetic induction to detect flaws in conductive materials. The eddy current test set-up consists of a circular coil which is placed on the test surface. The alternating current in the coil generates changing magnetic field which interacts with the conductive test surface and generates an eddy current. The flow of eddy current can be disrupted due to change in resistivity or conductivity, magnetic permeability, any physical discontinuities. The change in eddy current flow and a corresponding change in the phase and amplitude is measured against known values.
Eddy current test method can detect very small cracks in or near the surface of the material, the surfaces need minimum preparation.The biggest advantage of the eddy current test method is that is can be employed to determine surface flaws on painted or coated surface. Eddy current flaw detection is commonly used in the aerospace industry, crane industry, concrete pumping industry and other general industries where the protective surface coating cannot be removed.
The crane industry and crane owners benefit most from the application of eddy current test method to detect surface flaws underneath the protective coating (paint ). The exorbitant cost of paint removal and repainting is eliminated by applying eddy current flaw detection method as compared to magnetic particle test. It is also useful for making electrical conductivity and coating thickness measurements. Eddy current test is commonly employed for rapid thickness testing of coatings – conductive and non-conductive.
The principle of eddy current test which measures the change in resistivity in the conductive material makes it useful in wide range of applications such as conductivity measurement, sorting of material, assessment of heat treatment condition, sorting of materials on the basis of hardness and strength, the thickness measurement of thin components.
Compared to other surface flaw detection methods, eddy current test requires highly trained, skilled and experienced technicians. TUVsw professionals are qualified, certified and experienced in eddy current test.