Расчетная оценка характеристик малоцикловой трещиностойкости оболочковых элементов, работающих в сероводородсодержащих средах и при отрицательных температурах

Abstract

Background Analysis of failure and destruction of pipelines, oil and gas equipment and hydrocarbon storage tanks after long-term operation shows that the main cause of basic elements mechanical failure is the loss of carrying capacity expressed in embrittlement of the metal under the various factors, including low temperatures. In recent years a number of regulations on structural analysis of oil and gas pipelines specify an assessment of the critical stress intensity factors K c and their average value  oð. However, at present there are no avowed or adequate methods of quantitative assessment of oil and gas equipment and pipelines safety based on time criteria and fracture processes reflecting changes in thermal strain state and depressurization of the basic bearing elements, in particular pressurized environmentally hazardous corrosive operating media at subzero temperatures. Aims and Objectives To investigate the correlation of low-cycle fatigue life and service life of the basic elements of oil and gas equipment and pipelines under the action of pulse change of internal pressure causing low-cycle fatigue. Results There are provided the assessment of the quantitative correlation characteristics of basic elements low-cycle fatigue life for various equipment and pipelines and static stretching of standard specimens for uniaxial tensile in air and in hydrogen sulfide environments as well as at low temperatures. It was proved that the degree of low-cycle fatigue life is not constant, but varies depending on the work-hardening coefficient of the steel from one to two. There are obtained the formulas for calculation of various shell – type elements durability for equipment and pipelines under low-cycle loading applying the fracture toughness criteria for different operating environments.