Application of SINTAP to the safety assessment of X65 pipeline steel

Abstract

The recently developed European flaw assessment procedure, structural integrity assessment procedure(SINTAP) is applied to assessment for welded joints of the API 5L X65 pipeline steel with an assumed embedded flaw and surface flaw at the weld toe. As one of the basic input data, fracture toughness crack tip opening displacement (CTOD) tests are conducted at 0 ℃ and performed according to the requirements of the standard of BS7448. For the heat affected zone (HAZ) specimens, the microstructure observation is performed to insure that the tip of the crack is located in the coarse grain zone. The result explains the dispersity of the test values. In structural integrity assessment procedure-fracture assessment diagram(SINTAP FAD) method, the failure curves of welded joints at level 1 and 3 are derived from the tensile test results. The results of the assessment show that all assessment points are located within the failure lines of analysis level 1 and 3. So the welded joint of the pipeline is safe. This study laid the foundation of application of SINTAP to pipeline structure assessment.