Considering the limitations of visual and ultrasonic testing, an eddy current based technique was developed for detection of surface cracks on the inside cladded surface of RPV. It was observed that it was possible to detect an EDM notch of 1 mm deep on the cladded RPV surface.
How does eddy current testing work?
In eddy current testing, a coil carrying an AC current is placed close to the specimen surface, or around the specimen. The current in the coil generates circulating eddy currents in the specimen close to the surface and these in turn affect the current in the coil by mutual induction.
What can eddy current detect?
Eddy current testing is a non-destructive testing (NDT) inspection method used for a variety of purposes, including for flaw detection, material and coating thickness measurements, material identification and establishing the heat treatment condition of certain materials.
What are the disadvantages of eddy current inspection?
A primary disadvantage of ECT is that it only works with a current, meaning it cannot be applied to non-conductive materials. It's also non-conductive with ferromagnetic materials, as ECT equipment is subject to permeability changes on the welds.