Eddy Current Testing of Conductive Tubes With the Employment of the I-Core Sensor

Eddy current testing of tubes made of materials conducting electric current enables scrutinising their structure, geometric dimensions, and detecting flaws, thus limiting the risk of leakage and failure. This paper deals with investigating the feasibility of performing effective inspections in which the sensor is inserted into the interior of the tube. In the first step, a numerical model was created using the finite element method, and afterwards, two I-core sensors with a similar number of turns but of different geometrical dimensions were constructed. Both sensors have a removable core, thanks to which the influence of the core on the impedance of the sensors was examined. The utilised ferrite cores were of two types: with an air gap and without an air gap. The measurements were carried out for tubes made of magnetic and non-magnetic steel. Defects of different shape and different geometric dimensions were made in the tubes. In all cases, the changes in resistance and reactance for the I-core sensor were many times greater than for the air-core sensor. At the same time, the obtained results confirmed the effectiveness of internal inspections of conductive tubes with the use of the constructed sensor.