This presentation outlines recent developments in an emerging non intrusive sensing technique developed to detect localised abnormal pipe wall stress by mapping variations in the earth’s magnetic field around buried pipelines and insulated pipework in processing plant. Corrosion, metallurgical defects and ground movements result in areas of increased localised stress and a direct relationship has been described mathematically relating magnetic field characteristics to the magnitude of stress due to magnetostriction. The method is non invasive and in addition to reporting localised stress also can present a 3 dimensional map of the pipeline route and report % bending strain in pipelines subject to earth movement in geohazardous regions.

The presentation first explores magnetostriction in ferromagnetic materials and then how measurements of remote magnetic field can be applied to define the location of defects in operational pipelines and quantify the associated increase in localised stress. The benefits of using this technique and a series of case studies are described to illustrate statistically the accuracy of its predictions in the field. The presentation will be of interest to all engineers and managers involved in the integrity of pipelines and corrosion under insulation in pipework.