Characterisation of adjacent pits with combined application of MFL and laser scanning techniques

The most common corrosion defect found in pipelines is adjacent pits. Adjacent pits are a group of individual pits interacting with each other. Due to their geometry, discriminating between these defects and accurately sizing them is not possible using the traditional magnetic flux leakage (MFL) technique. Significant improvements in depth sizing accuracy can be obtained if sizing models can be optimised on high-resolution data that allows the shapes and actual dimensions of the adjacent pits to be more clearly discerned. This paper presents a new combination method of MFL and high-resolution laser scanning techniques for improving the accuracy of depth sizing of adjacent pits. MFL and laser scanning experiments have been conducted in a laboratory set-up on pits with different edge-to-edge distances. The results of the new combination method reveal how the additional laser scanning data, which allows increased distinction of individual pits, can help the MFL sizing model and improve the depth sizing accuracy.