Quantitative Evaluation of Oil Pipeline Cracks Using an Electromagnetic Acoustic Transducer and Numerical Simulation

Abstract

Defect detection is of great importance in the oil and gas industry. Early defect detection prevents structure failures leading to safe operations and to non-negative economic impact. Quantifying the depth of a defect is achievable using ultrasonic guided waves and Electromagnetic Acoustic Transducers (EMAT). Producing Lamb waves and using their dispersive properties, the velocity variations of these waves travelling within the pipe boundaries can be converted into thickness using a fixed frequency. The Simultaneous Iterative Reconstruction Technique (SIRT) algorithm is employed to achieve this quantification and obtain a thickness map of the pipeline. This project aims to successfully detect hole type and corrosion type defects through experimentation and numerical simulation using the proposed algorithm in both cases. The corrosion defect to identify is 1mm depth at its deepest point, 10.5mm long and 20mm wide. The hole defect type are three 2mm diameter holes aligned with the pipeline axis. Processing the signals obtained from the guided waves we obtain the arrival times to convert it into velocity and further conversion into thickness using the dispersive relationship of the Lamb waves. Doing this for the base cases, a pipeline with no defect and the pipeline in the presence of a defect, it is possible to obtain a thickness map of the area where the waves travelled and collected information for the denominated area of interest. Comparing the signals obtained when the algorithm is implemented, we are able to identify a thickness variation and determine whether a defect exists or if the pipeline is clean.