A pipeline inspection gauge based on low cost magnetic flux leakage sensing magnetometers for non-destructive testing of pipelines

Abstract

The aim of this paper is to test if cost-effective off the shelf magnetometers and permanent disc magnets can be utilized to introduce a new method of low-cost Magnetic Flux Leakage (MFL) based Non-Destructive Testing (NDT) in the field of In-line Inspection (ILI) of ferromagnetic pipelines. During the course of experimentation the Anisotropic Magneto-resistive (AMR) and Tunneling Magneto-resistive (TMR) magnetometers were utilized which are commercially available low-cost prepackaged magnetometers available as digital compass breakout boards. Also employed were ceramic permanent disc magnets fixed circumferentially in the PIG assembly to generate the flux. Finally, the flaws that were tested were introduced into the mild-steel pipeline specimens, to generate MFL, were machined flaws of the slit and pinhole types of 2mm, axial length and diameter, respectively and a dent of approximately 6mm area. The results of the experiment show that off the shelf AMR and TMR magnetometers, coupled with permanent magnets, can detect flaws in ferromagnetic pipelines and provides an alternative to conventional expensive PIGs and ILI in use in the industry today.