Stress and Strain State of a Gas Pipeline in Conditions of Stress-Corrosion

It is shown that in the analysis of causes of stress corrosion cracking (SCC) of gas pipeline (GP) insufficient attention is paid to the role of mechanical stresses. In the paper it is underlined that by consideration of SCC causes it is necessary to take into account real distortions of the form of cross-sections of a pipeline. These are ovality of cross-sections and, the main, dents. Conditions of occurrence of these defects of the form of cross-sections of pipes are considered. The kinds of stress and strain state (SSS) in GP are analysed. The techniques are developed of assessment of the level of residual strains in the area of distortions of the form of cross-sections of pipelines as well as of determination of stresses and strains in them at action of internal pressure. The technique is based on the theory of elastic thin shells. It is shown that through-wall -thickness stresses which were ontained by the technique can considerably exceed the yield stress of steel even for shallow dents. Conclusions are given about necessity to account for stresses in GP in the analysis of SCC causes as well as about necessity of standardizing allowable levels of these stresses.