State of the art on mechanical properties and fitness-for-service assessment of high-grade pipeline girth weld

The girth weld is the weak link of high-grade pipeline, and its structural integrity affects the safety of pipeline operation. Herein, the state of art of the weld metal strength and toughness indicators were discussed from three aspects: the design method of weld metal strength and toughness indicators, the strength and toughness acceptance indicators proposed by pipeline engineering design standards, and the test method of weld metal strength and toughness. The fitness-for-service assessment methods of pipeline girth weld were expounded. The key problems and progress of the assessment methods were discussed: the crack tip constraint effect of fracture toughness, the numerical simulation method of fracture behavior of pipeline girth weld, the evaluation method of crack driving force, the assessment method of failure evaluation diagram, the prediction method of tensile strain capacity of pipeline girth weld, and the fracture experimental test of full-scale pipeline girth weld. Finally, the existing problems and future research directions in the mechanical properties and fitness-for-service assessment of high-grade pipeline girth weld were put forward. Generally, the research results could provide a reference for improving the intrinsic safety of high-grade pipeline girth weld.