Magnetic non-destructive testing methods can be classified into the earliest methods developed for assessment of steel constructions. One of them is the magnetic flux leakage technology. A measurement of the magnetic flux leakage is quite commonly used for examination of large objects such as tanks and pipelines. Construction of a magnetic flux leakage tool is relatively simple, but a quantitative analysis of recorded data is a difficult task. Therefore, methods of magnetic flux leakage signal processing and analysis are still under development. A magnetic flux leakage in-line-inspection tool called FLUMAG 500 was constructed. FLUMAG 500 was designed for gas and oil pipelines inspection. In this paper principle of operation of FLUMAG 500 was described. Advanced algorithms of the signal processing and analysis was also developed. Results coming from the development stage as well as from the final construction of the tool were presented. Analysis of these results shows that FLUMAG 500 is a suitable tool for detection of corrosion defects in a pipeline wall.
The magnetic flux leakage (MFL) technique is extensively used for detection of flaws as well as for evaluation of their dimensions in ferromagnetic materials. However, proper analysis of the MFL signal is hindered by the MFL sensor velocity causing distortions of this signal. Traditionally measured components of the MFL signal are particularly sensitive to the scanning velocity. In this paper, an another signal – the gradient of the normal component of magnetic flux density – was proposed as it is less sensitive to the scanning velocity. Results obtained for scans of the steel plate with artificially manufactured flaws confirm this statement.