A review of crack growth models for near-neutral pH stress corrosion cracking on oil and gas pipelines

Abstract

This paper presents a review of four existing growth models for near-neutral pH stress corrosion cracking (NNpHSCC) defects on buried oil and gas pipelines: Chen et al.’s model, two models developed at the Southwest Research Institute (SwRI) and Xing et al.’s model. All four models consider corrosion fatigue enhanced by hydrogen embrittlement as the main growth mechanism for NNpHSCC. The predictive accuracy of these growth models is investigated based on 39 crack growth rates obtained from full-scale tests conducted at the CanmetMATERIALS of Natural Resources Canada of pipe specimens that are in contact with NNpH soils and subjected to cyclic internal pressures. The comparison of the observed and predicted crack growth rates indicates that the hydrogen-enhanced decohesion (HEDE) component of Xing et al.’s model leads to on average reasonably accurate predictions with the corresponding mean and coefficient of variation (COV) of the observed-to-predicted ratios being 1.06 and 61.2%, respectively. The predictive accuracy of the other three models are markedly poorer. The analysis results suggest that further research is needed to improve existing growth models or develop new growth models to facilitate the pipeline integrity management practice with respect to NNpHSCC.

Full‐scale testing of near‐neutral pH stress corrosion cracking growth behavior of a vintage X52 oil pipe

“…As the saw-cut length is made far larger than the depth of the crack, its propagation is considered primarily in the through wall thickness direction, while the length growth is assumed to be negligible. 3,22 This is consistent with the observations shown in Figure 4.…”

“…2 The simultaneous presence of three factors, namely, the tensile stress (mechanical factor), susceptible microstructure (metallurgical factor), and corrosive environment (electrochemical factor), is considered essential for the initiation and growth of SCC. 3 Two types of SCC have been discovered on buried pipelines, namely, high pH SCC and near-neutral pH SCC (NNpHSCC). Since its first discovery in Canada in the mid-1980s, NNpHSCC 4,5 has generated significant interests in the Canadian pipeline industry.…”

An information entropy-based risk assessment method for multiple-media gathering pipelines

“…Backfilling method (6) Both process and method are correct (2); Process is correct but the method is incrorrect (4); Both backfill process and method are incorrect (5); None (6).…”

“…Compared with long-distance pipelines, unrefined transport media can cause more serious internal corrosion [2][3][4]. Besides, the operating environment with high uncertainties will cause the gathering pipeline failure, seriously affecting upstream production, environmental pollution, and even casualties [5][6][7][8]. Although this is well-known in the industry, the statistical data show that failure accidents of gathering pipelines are rising [9].…”

An information entropy-based risk assessment method for multiple-media gathering pipelines

“…Compared with long-distance pipelines, unrefined transport media can cause more serious internal corrosion [2][3][4]. Besides, the highly uncertain operating environment will also cause the failure of gathering pipelines, seriously affecting upstream production, environmental pollution, and even endangering life [5][6][7][8]. Although this is well-known in the industry, the statistical data show that failure accidents of gathering pipelines are rising [9].…”