Savula R. Ensuring the efficiency of gas main pipeline during long-term operation in the highlands

The thesis is devoted to research, which is aimed at ensuring efficiency of gas main pipeline during long-term operation in the highlands by improving the methods of the stress-strain state analysis and strength assessment based on the degradation of pipe material, deviation from linearity route and the presence of local plastic deformation. The structural changes that occur in steel gas mains during prolonged use are researched. The effect of the tubular steel aging process and plastic deformations of local gas mains on physical and operated steel mechanical properties is estimated. The obtained quantitative estimates of the mechanical characteristics of steel pipe enable specification of acceptable conditions of pipelines in view of both process and temperature loads. The process of elastic-plastic deformation during pipe laying gas mains in a trench on the curved track is analysed, as well as during major repairs of pipeline replacement coil and defined points that should develop centering device. In this work is researched the influence of residual stresses due to local plastic pipeline deformation on the stress-strain pipe state. Experimental study of elastic-plastic deformation was held, as well as study of the tube strength in the laboratory to test the assumptions adopted in theoretical studies and the study of patterns of coercive strength change of tubular steel 17Г1С during operation.