Pulsed Eddy Current (PEC) is a nondestructive examination technique used for detecting flaws or corrosion in ferrous materials or measuring the thickness of objects.
The principles of eddy current testing were first laid out in 1831. This was the year with Michael Faraday discovered electromagnetic induction. Eight years later these basic principals led to a new discovery. Researchers discovered that the properties of a coil would change when placed in contact with metals of different connectivity and permeability. It wasn't until World War II that these principles found practical use though.
PEC works using the principle of electromagnetic induction. When applying step function voltage to a conductor, a magnetic field develops around it. This field changes in intensity as the current alternates. If brought close to the first field, another conductor will have a current induced in it as well. If there are any flaws in this material then the eddy current will distort. In the case of PEC, the first conductor is an eddy current probe. The second is the test material.
The main advantage of PEC over conventional eddy current is that it contains a continuum of frequencies. Because of this, it is possible to measure the electromagnetic response to several different frequencies can with just a single step. Information from a range of depths can be obtained all at once.
PEC can be done without need for contact with the surface of the material. Because of this, it can be useful in situations where an object’s surface is rough or inaccessible. This method also doesn’t require surface preparation or removing any insulation. It can be a quick and cost-effective solution for corrosion detection.
PEC is widely used for a number of applications. These include both measuring the thickness of steels and detecting corrosion. It can be used on materials as diverse as vessels, columns, storage tanks and spheres, piping systems, and structural applications with fireproofing. Furthermore, it can be used on both insulated and uninsulated materials.
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