Magnetic Flux Leakage Technical Articles
Click a technical paper title to view the associated paperMagnetic Flux Leakage Technology - JC Drury
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Magnetic Flux Leakage (MFL) technology has been used in the monitoring of Underfloor or Far Side (FS) corrosion for about 11 years. Silverwing (UK) Ltd entered the field ten years ago, in 1991. As with all Non Destructive Testing methods, MFL has both advantages and disadvantages, as well as pitfalls for the unwary. This paper attempts to explain the underlying principles of the method and highlights the advantages, disadvantages and pitfalls.
A comparison of the magnetic flux leakage & ultrasonic methods in the detection & measurement of corrosion pitting in ferous plate & pipe - JC Drury
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presented at the 15th World Conference in Rome 2000
Magnetic Flux Leakage (MFL) and manual Ultrasonics (UT) have been used extensively for the detection and sizing of corrosion pits in ferrous plates and pipes. Users and providers of these inspection services may have different perceptions and expectations of the sensitivity and accuracy of the methods. This paper discusses the underlying principles of the methods and their effect on Probability of Detection (POD) and accuracy. It addresses the limitation on accuracy of the ultrasonic method due to pit shape and reflectivity, and also, for the first time, takes a quantitative look at the effect of pit volume on MFL results.
Corrosion pitting - How good is manual ultrasonics? - JC Drury
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presented at the ASNT Fall conference 2000 Indianapolis
During the last three years my interest in the use of ultrasonics for the detection of corrosion and the measurement of remaining wall thickness has been re-awakened. The method has been extensively used to verify and quantify Magnetic Flux Leakage (MFL) results. Discrepancies between ultrasonic and MFL results have usually been put down to "Another MFL false - call." However, having watched many ultrasonic tests being carried out, I have come to believe that the boot is often on the other foot and that we place too much faith in the ultrasonic method for corrosion monitoring. The techniques used by many practitioners give rise to serious shortcomings in both probability of detection, and accuracy of remaining wall assessment. These shortcomings are not confined to corrosion monitoring of flat plate, but apply equally to pipe and vessel inspection. This paper looks at the root causes of poor performance with ultrasonics and suggests some methods to improve the situation.
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