Decoupling the Influence of Wall Thinning and Cladding Thickness Variations in Pulsed Eddy Current Using Principal Component Analysis

Abstract

Corrosion may develop and grow on steel pipes under layers of insulation and cladding. Inspection of the pipes through these protective layers is of paramount importance. Pulsed eddy current (PEC) is a primary non-destructive testing (NDT) technique candidate for this type of inspection as it requires no contact with the inspection material. To overcome the variability in PEC signals due to variations in the cladding thickness, a large measurement set is analysed in this paper using principal component analysis (PCA). The PCA approach decomposes the signal set into a number of uncorrelated variables that explain the maximum amount of the variance in the data set, in which, in this respect, efficiently separate the influences contributed by the difference in the material properties of cladding and pipe wall. The feasibility of using PCA to quantify simulated steel pipe wall independent of confounding cladding thickness variations is investigated. It is found that, with sufficient amount of data, the approach can effectively separate the influences contributed by the wall thickness variations from the cladding thickness variations.

Circular-arc array for the pulsed eddy current inspection of thermally insulated pipelines

“…Extensive studies on the application of the PEC technique in the CUI inspection of pipelines have been conducted to improve the inspection performance for metal pipes [15][16][17][18][19][20][21][22]. Fundamental studies of the analytical and numerical solutions of PEC testing of layered structures have been undertaken in [15,16].…”

“…Fundamental studies of the analytical and numerical solutions of PEC testing of layered structures have been undertaken in [15,16]. A three-dimensional finite element model of pipeline corrosion defects was established in [17,18], and the distributions of the current and induced magnetic fields in the pipeline under various defect volumes were simulated. The inner wall flows in the pipe under insulation were detected using the PEC testing method [19], in which a conventional coil probe was used.…”