Burst Tests on Pipeline Containing Closely Spaced Corrosion Defects
In this paper the burst tests of five tubular specimens are presented. In these tests the tubular specimens were loaded with internal pressure only. The specimens were cut from a longitudinal welded tube made of API 5L X80 steel with a nominal outside diameter of 457.2 mm (18 in) and a nominal wall thickness of 7.93 mm (0.312 in). The specimen IDTS 8 contains only one defect, herein called base defect. The base defect is an external flat bottomed defect with uniform width (circumferential dimension). The other four specimens contain groups of interacting defects constituted by the combination of three or more base defects. All the defects were machined using spark erosion. Measurements were carried out in order to determine the actual dimensions of each tubular specimen and its respective groups of defects. Tensile specimens and impact test specimens were tested to determine material properties. The failure pressures measured in the laboratory tests are compared with those predicted by five assessments methods, namely: the ASME B31G method, the RSTRENG 085dL method, the DNV RP-F101 method for single defects, the RPA method and the RSTRENG Effective Area method.