A random field model of external metal-loss corrosion on buried pipelines: Fid-Bau Portal

A random field model of external metal-loss corrosion on buried pipelines

Bao, J. / Zhou, W.

Highlights • Propose a random field model to simulate corroded external surfaces of buried pipelines. • Addresses the intermingling of corroded and corrosion-free areas on the pipe surface. • The model employs a latent Gaussian field and a spatially dependent threshold. • Model parameters are estimated based on high-resolution laser scan data.

Abstract This paper proposes a random field model to characterize the corrosion depth on the external surface of buried steel oil and gas pipelines. The model addresses the intermingling of corroded and corrosion-free areas on the pipe surface, similar to the spatial intermittency of rainfall accumulation within a geographic area, by using a latent homogeneous Gaussian random field and a spatial position-dependent threshold associated with the latent Gaussian field. High-resolution corrosion measurement data obtained from corroded pipe segments removed from in-service pipelines are used to estimate parameters of the proposed model, including the probability of corrosion at a given point, marginal distribution of the nonzero corrosion depth and correlation structure of the latent Gaussian field. The results indicate that the nonzero corrosion depth follows a shifted lognormal distribution. The isotropic γ-exponential correlation function is adequate to characterize the correlation structure of the latent Gaussian field with the correlation length varying from 17 to 50 mm and γ from 0.69 to 0.82. A comparison of simulated and measured corrosion fields suggests that the proposed model is able to capture the characteristics of naturally-occurring corrosion field on the pipe surface. The proposed model provides a useful tool for developing fitness-for-service assessment methodologies for corroded pipelines.