Detection and Measurement of Pitting Corrosion using Short Range Guided Wave Scanning

Short range guided wave scanning is an inspection method enabling an indirect, quantitative measurement of remaining pipe wall thickness. It has seen widespread industrial use as an inspection solution for corrosion under pipe support (e.g. [1]). Pitting corrosion represents a significant challenge in industrial pipelines and its presence complicates short range guided wave scanning analysis as the wavelength used for inspection is larger than the diameter of small pitting-type defects. This work investigates the reflected signal from pitting corrosion, both in isolation and in the presence of larger corrosion patches, to improve the understanding of the complex signals received. This work provides the foundation and guidance for analysis techniques used in guided wave scanning. To achieve this a series of representative pitting defects with varying diameter and depth have been investigated using explicit finite element modelling. It is shown that using currently established analysis techniques, the pit depth can be quantified for pitting with a diameter larger than approximately 13 mm. Smaller diameter pitting may only be qualitatively detected at this time due to mode conversion occurring at the defect, which obscure features that are used to provide quantitative analysis of the defect depth. Quantitative sizing of defects where pitting is present will require further investigation.