Girth weld cracking is one of the main failure modes in oil and gas pipelines; girth weld cracking inspection has great economic and social significance for the intrinsic safety of pipelines. This paper introduces the typical girth weld defects of oil and gas pipelines and the common nondestructive testing methods, and systematically generalizes the progress in the studies on technical principles, signal analysis, defect sizing method and inspection reliability, etc., of magnetic flux leakage (MFL) inspection, liquid ultrasonic inspection, electromagnetic acoustic transducer (EMAT) inspection and remote field eddy current (RFDC) inspection for oil and gas pipeline girth weld defects. Additionally, it introduces the new technologies for composite ultrasonic, laser ultrasonic, and magnetostriction inspection, and provides reference for development and application of oil and gas pipeline girth weld defect in-line inspection technology.

The rapid development of offshore oil and gas resources in recent years has led to a steadily growing importance of the safety of offshore pipelines. Active faults are some of the main geological hazards to which onshore and offshore pipelines may be subjected. In this study, an improved analytical method for estimating the strains in offshore pipelines subjected to strike-slip fault displacement was proposed. The pipe steel was considered as a linear strain hardening material and the soil constraint on pipe was considered as a series of elastic–plastic nonlinear soil springs. Explicit solutions for pipe elongation under fault displacements were derived and a high efficient iterative algorithm was proposed for accurately estimating the strains in the pipe. Better agreements with finite element results were obtained for the pipe strains derived using the proposed model when compared with the previous analytical method (i.e. Newmark method). This study is therefore considered to be a good reference for the design and safety evaluation of offshore pipelines crossing active faults.