When assessing the strength of pipes with defects such as "metal delamination" at the stages of construction, operation and repair of main pipelines in the oil and gas complex, we should take into account the influence of the location, shape, size and places where metal delamination comes out to the pipe surface on the stress concentration in the pipe walls near metal delamination and the strength of the pipe walls. The analysis of stresses in the walls of pipes of the main pipeline with defects of the "metal delamination" type was performed by the finite element method using the ANSYS software package. Stress calculations were performed for a pipeline section with three types of defects: metal delamination without reaching the surface (inside the pipe wall); metal delamination with access to the inner surface of the pipe; metal delamination with an exit to the outer surface of the pipe at three different values of the internal working pressure (the pressure at the current operating mode of the pipeline, the design pressure and the test pressure). To identify the types of delaminations that create the highest stress concentration, an analysis was made of calculating the maximum stresses in the sections of the pipeline with delaminations that have access to the inner and outer surface of the pipe wall, and without exit to the surface, and the maximum stresses on the inner surface of the wall pipes on a defect-free section at various values of the internal working pressure. The zones of stress concentration are determined under various values of the internal working pressure. Comparison of the calculated resistance of the metal of the pipe wall in terms of yield strength with the maximum stress values in the zones of stress concentration in the places where delaminations emerge on the inner and outer surfaces of the pipe wall at various values of the internal working pressure for various categories of pipelines and their sections to check the safety margin strength.
References
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