The environmental effect of corrosion can cause nucleation and growth of stress-corrosioncaused cracks on the external surfaces of gas-pipeline tubes, thus leading to accidental breakdowns. Peculiar features of corrosive and stress-corrosive flaws along a pipeline route are analyzed in this study and probable reasons for nucleation and propagation of stress-corrosion-caused cracks are discussed. The selectivity of cracking, detected by a nondestructive testing technique and manifesting itself on various scales, or localization of stress-corrosive cracks in single tubes or GMP sections can have different causes and are determined by both the initial state and manufacturing parameters of tube production and the ensemble of environmental conditions (inhomogeneity of the corrosive activity of the ground-extracted electrolytic solution), especially as they pertain to corrosive damage. The presence or absence of cracks in a GMP section with signs of SCCC is determined by the presence of single tubes with tendencies toward cracking or nucleation of stress-corrosive cracks. The selectivity of cracking of single tubes is determined by a particular state of these tubes and is not related directly to local environmental conditions. Gradual exhaustion of SCCC nuclei with an increase in the nonfailure operation time of an operating system of GMPs and natural 'extinction' of SCCC can be suggested on the basis of obtained data of in-tube nondestructive testing.
Possible reasons for selectivity of corrosive tube cracking in underground gas-main pipelines
Mögliche Ursachen des selektiven Korrosionsbruchs an Rohren bei unterirdischen Gas-Hauptleitungen
Russian Journal of Nondestructive Testing ; 41 , 6 ; 403-407
2005
5 Seiten, 2 Bilder, 1 Tabelle, 5 Quellen
Aufsatz (Zeitschrift)
Englisch
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