(METHOD FOR ASSESSING MAIN PIPELINE STRENGTH CONSIDERING ELASTOPLASTIC STRAIN)
Strength of the main pipelines should be controlled in use to ensure reliable and trouble-free operation. For this purpose, pipeline condition is usually monitored with strain gauges, for example. They transmit information represented by pipe wall strain values. While the algorithms for processing strain gauges data under elastic strain are known and widely used, the algorithms for calculating the components of stress-strain state in the elastoplastic phase based on strain measurements have not been developed or, at least, are not described in publications. At the same time, hazardous sections of pipelines close to or within the limit state may be operated in elastoplastic strain mode and have defects. This article is focused on addressing this issue.
The author has developed the algorithm for calculating the components of pipeline stress-strain state based on formulas derived from the deformation theories of plasticity. Stress-strain relation beyond elasticity limits is defined by exponential function. Actual safety factor calculated as the ratio of the ultimate strength of steel to pipe wall stress intensity is used as the strength criterion.
The article contains diagrams of the main pipeline strength assessment based on the developed strength calculation algorithm. They allow you to rank pipe sections into three groups: hazardous, potentially hazardous, and non-hazardous. The list of activities to maintain pipeline system reliability should be determined according to the hazard category. Also, the proposed method will be helpful in prioritising repair of pipeline sections based on the actual safety factor value.
A.A. Ignatik, PhD in Engineering, Ukhta State Technical University (Ukhta, Russia), email@example.com
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