A study on evaluation method of local pipe wall thinning based on DC potential difference measurement

Abstract

In this study, a simple method to evaluate the local pipe wall thinning by using the DC potential difference method was examined. The pipe has outer diameter D and thickness t₀. The local inner-wall thinning is modeled as a back wall slot having arc-shape cross section of width 2w and depth b. The constant DC current is applied to the pipe through two probes, and the distribution of potential difference between current input and output probes is measured. The potential differences measured before and after thinning are represented as V₀ and V₁, respectively. The thinning depth b/t₀ is evaluated from the maximum value of V₁/V₀. Three-dimensional finite element method was used to analyze the relation between thinning size and potential difference for various cases. As a result, it was shown that the relation between b/t₀ and V₁/V₀ is affected by w/D. The calibration equation between b/t₀ and V₁/V₀ was obtained by approximating FEM results, and its validity was shown by numerical experiments.