Flux Leakage Testing
Stray flux testing is an electromagnetic method for detecting wall thinning and internal flaws in ferromagnetic pipes or plates. The part is magnetized, and the emerging stray flux is measured with sensors.
Physico-chemical mechanism of action
Magnetic flux leakage testing uses the properties of the electromagnetic field. A component is magnetized to saturation, meaning it is fully embedded in a magnetic field. If the material has an irregular structure, such as a wall thickness reduction or an internal flaw, the escaping leakage flux changes. These changes are detected by sensors and visualized.
Metallurgical relevance & risks in welding
Magnetic flux leakage testing is especially important in the welding industry to ensure that weld defects or internal flaws are not overlooked. An irregular leakage flux can indicate deformations, cracks, or uneven weld volumes. Without proper testing, such flaws can lead to further defects that may cause safety issues or malfunctions later in service.
Workshop practice & instructions
To perform magnetic flux leakage testing, the component must first be fully magnetized. This is done in a special magnetic field. Then the escaping leakage flux is measured with sensors and displayed on a visualization. It is important that the test is carried out under the right conditions to get reliable results. Temperature and environment should be controlled so that no external interference affects the measurement.