S.A. Shotskiy, General Director PAO GEOTEK, Moscow, Russia S.L. Golofast, Dr. Sci. (Eng.), Prof., SGolofast@gazpromproject.ru OOO Gazprom Proyektirovaniye, St. Petersburg, Russia
Calculation of the values of stresses occurring in the pipe wall, and subsequent verification of the fulfillment of the strength condition ensuring the elimination of unacceptable plastic deformations, and, as a consequence, safe operation of the pipeline shall be conducted on the basis of the deterministic methods. Specific character of these methods is that the excessive internal pressure included in the design dependencies is adopted as a constant value and the same for all the linear sections of the pipeline. Due to this assumption, the dispersion limits and distribution laws of this value, which are not only individual for each linear section but also change over the time during pipeline operation, are not considered. The calculation results based on the deterministic methods of stresses and movements in the subterranean pipeline, as well as the parameters of the weight coatings allowing to reduce the value of stresses occurring in the pipe wall on the curved temperature-deformable sections, do not reflect the actual strength of the pipeline, and do not ensure effective application of the weight coatings. They do not consider not only the random, but also the differential nature of the excessive external pressure on each of the linear sections. The article presents the results of stress calculation and movements occurring in the vertical plane of the underground main gas pipeline loaded with distributed along the convex section continuous load from the top of its angle of rotation. Considering the random nature of the value of the excessive internal pressure, the strength of various linear sections of the main gas pipeline was evaluated. An individual approach was substantiated concerning the selection of the parameters of the continuous weight coating due to specifics and differences in the distribution laws and limits of changes of the internal pressure at various linear sections of the main pipeline.
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