Chapter 36 STRESS CHARACTERIZATION OF MECHANICAL DAMAGES IN GAS PIPELINES USING LARGE STANDOFF MAGNETOMETRY TECHNOLOGY Available to Purchase

Large standoff magnetometry (LSM) is an emerging non-intrusive, above ground, passive geo-magnetization flux leakage inspection technology used to detect pipeline features or anomalies associated with elevated local stresses. The stress estimation and characterization are the important part of the LSM technology and need to be understood properly so that the LSM output stresses are correctly analyzed and assessed for the anomalies in the pipeline. For this purpose, the present paper briefly reviews the Stress Concentration Tomography (SCT) -one version of the LSM technology, including its advantages, capacities, limitations, challenges and practical uses as well. Theoretical basis of SCT technology and its equivalent stress definitions are discussed. Followed are two field trial examples of LSM inspection results of mechanical dents in operating gas pipelines. With the dent profiles measured by ILI or in-ditch NDE, the finite element analyses (FEA) are performed to determine stresses of the dents in the gas pipelines in three-dimensional conditions. Then the FEA stresses and the LSM estimated stresses local to stress concentration zones or dents are comparatively analyzed to show their differences for the selected plain dents found in the two field trials.