Estimation of static strength of sections of the linear pipeline portion with a colony of corrosion fine cracks

This paper presents the proven analytical apparatus for determining the complex stress state in the material of the linear part -main pipeline with stress corrosion cracking in the form of fine crack colonies. The critical stresses are defined and an analytical dependence for calculation of the allowed internal pressure for the damaged pipeline, not satisfactory to strength conditions is received. The above calculation model of stress state is different from their counterparts in that it is not limited by standard methods based solely on the weakened section, and takes into account the stress concentration in the surface defect zone, which has a positive effect on the accuracy of estimated parameters. Introduced additional conditions during selection of permissible stresses ensures the correctness of strength calculations, especially in cases where there are corrosion cracks with relatively large depth in the pipe wall. Additionally, in the present method it is possible to consider the influence of the thermal component to the complex stress state. The presented theoretical apparatus was confirmed with finiteelement modeling in Ansys Mechanical software environment. The results of the practical implementation of this work are given recommendations on assessing the technical condition of pipes with crack defects of different nature, as well as determination of the maximum allowable working pressure, which meets strength conditions on gas pipelines susceptible to stress corrosion cracking.