Apparatus and method for inspection of components made of electrically conductive material by partial saturation eddy current testing

摘要

An inspection tool fig. 2(a) for non-destructive testing of a component 17 made of electrically conductive material comprises one or more sensor modules employing rotationally movably mounted permanent magnets 27, which provide means for generating variable DC magnetic field 36 within the component, and eddy current probes 20 to provide means for performing a partial saturation eddy current test upon the component. The eddy current probe preferably comprises an integrated magnetic field sensor 21. In an inspection method a first step employs selecting a frequency and strength for AC current to drive eddy current coils 20. In a second step strength of DC magnetic field generated within component 17 is varied until permeability measured by Hall sensors 21 corresponds to a predetermined value. In a third step a partial saturation eddy current test is performed by scanning the sensor module over the surface of the component 17 to monitor the impedance signal detected by eddy current coils 20 and the magnetic field strength signals detected by Hall sensors 21. The signal detected by eddy current coils 20 indicates presence of defects and both signals can be analysed to identify defect type. Varying strength of DC magnetic field varies depth of penetration at which partial saturation eddy current test is performed. Permeability measurement also allows appropriate magnetic field density to be maintained throughout scan to compensate for variations in distance between sensor module and component. Apparatus and methods are suited for inspection of remotely located tubular components in the oil and gas industries, e.g. flexible risers.