Обоснование Величины Температурного Перепада При Расчетах Напряженно-Деформированного Состояния Длительно Эксплуатируемых Магистральных Газопроводов

When calculating the stress-strain state of main gas pipelines, thermal stresses constitute a fundamental component. According to the code of practice SP 36.13330.2012, the temperature differential maximum or minimum pipeline wall temperature during operation and the air temperature at the time of «fixing the design scheme» for a given pipeline section (the design reference period). However, the term «fixing the design scheme» is defined as the difference between the maxi-ambiguity in its interpretation. Previous versions of the standards used phrases such as «air temperature during backfilling» or «air temperature during the welding of tie-in joints», but these refer only to brief, intermediate stages. The temperature that most accurately corresponds to the «fixing of the design scheme» is the temperature of an underground section of a main gas pipeline-measured at the depth of its axis-following backfilling; the welded pipeline string may remain in this state for months or even years, during which time it becomes fixed and secured in its specific spatial (linear-vertical) position. Upon commissioning, when the gas temperature exceeds the «fixing» temperature (which corresponds to the soil temperature at the burial depth), the pipeline section shifts from its initial spatial position to a new one, dictated by the gas temperature and the design operatis not explicitly defined, which createsing pressure. The resulting stresses are primarily converted into bending radii, and in this new configuration, the pipeline becomes consolidated with the surrounding soil. Thus, the characteristic temperature of a main gas pipeline section during the initial stage of operation is, in fact, the temperature at which the «design scheme» is «fixed».The proposed method for evaluating the impact of thermal stresses allows for a more precise definition of the «fixing of the design scheme» temperature, thereby resolving the existing ambiguity. demonstrate the mechanism by which a pipeline section with design bend radii transitions into a section with non-compliant (substandard) bend radii; determine the stress-strain state in sections that have been in service for an extended period (30 years or more).