Eddy Current Testing or Eddy Current Inspection is one of several NDT methods using the principle of electromagnetism to conduct examinations. Other methods, such as remote field testing (RFT), flux leakage and Barkhausen noise, also use this principle.
Eddy Current Testing is completed through a process called electromagnetic induction. When alternating current is applied to the conductor, such as copper wire, a magnetic field develops in and around the conductor. This magnetic field expands as the alternating current rises to maximum and then collapses as the current is reduced to zero. When another electrical conductor is positioned in close proximity with this changing magnetic field, current will be induced into this second conductor. Eddy currents are induced electrical currents that flow in a circular path. Eddy Current testing takes its name from Eddies, which are formed when a liquid or gas flows in a circular path around obstacles under the right conditions.
ID probes, also referred to as Bobbin probes or feed-through probes, are inserted into pipelines or tubing to inspect from the inside out. ID probes have housing that keeps the probe centred in the product and maintain the orientation of the coil(s) constant relative to the test surface. The coils are most commonly wound around the circumference of the probe so the probe inspects an area around the entire circumference of the test object in one go.
Applus+ offers five NDT inspection methods for heat-exchanger tubing systems: