ESTIMATION OF THE ADMISSIBILITY OF CIRCULAR-CRACK-TYPE DEFECTS IN THE ZONE OF WELDED FIELD JOINTS OF MAIN PIPELINES

摘要

We have considered welded joints of rectilinear parts of underground or overground (in embankment) pipelines with point defects, which are modeled by internal circular surface cracks. We have determined their stressed state induced by the action of internal pressure, temperature drop between the mounting and operation temperatures, and technological residual stresses. On the basis of the two-parameter criterion of the mechanics of brittle-viscous fracture, with the use of failure assessment diagrams, we have calculated the coefficients of safety margin of such a part of the pipeline with a crack in the weld and the admissible defect sizes.