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In the conventional method of analysis for the remaining strength assessment of a corroded pipeline, von Mises failure criterion is used. This continuum-based modelling approach is unable to assess the cracking of the pipeline. In this study, a fracture mechanics approach is used for the assessments of burst pressures of pipelines with corrosion only defects, pipelines with crack-like defects and pipelines with crack-in-corrosion defects. The fracture mechanics approach with the J -integral was found to simulate successfully the burst pressures obtained from rapture tests of pipelines with corrosion only defects and crack-in-corrosion defects. The conventional von Mises stress-based approach and design equations can reasonably be used for predicting the burst pressures of pipelines with corrosion only defects. However, the fracture mechanics approach is required for pipelines with crack-like defects and crack-in-corrosion defects. A parametric study is presented with calculations of the J -integrals for pipelines with crack-in-corrosion defects for various crack depths and crack lengths. • A numerical study on the burst pressure assessment of corroded pipelines using a fracture mechanics approach is presented. • The fracture mechanics approach is found to model effectively the cracking and the failure of the pipelines. • The assessment using J-integral criteria provided a better prediction of the burst pressures for corroded pipelines. • The study reveals that a fracture mechanics approach is required for pipes with crack-like and crack-in-corrosion defects. • Calculation of J-integrals for pipes with crack-in-corrosion defects for various crack depths and crack lengths are presented. [ABSTRACT FROM AUTHOR]

Highlights • Effects of axial force and bending moment on the burst pressure of corroded pipelines are studied. • Burst pressure is significantly reduced under compressive axial force and closing bending moment. • Developed failure loci considering axial forces, bending moments and internal pressures. • The failure loci are found to depends on corrosion depths and load combinations. • The failure loci can be used for burst pressures assessment with known axial force and bending moment. Abstract The remaining strength of corroded pipeline is generally assessed considering the internal pressure only. However, pipelines are often subjected to axial forces and bending moments due to external loadings, which may significantly reduce the burst pressure of the pipeline. This paper presents a study using finite element analysis on the effects of axial forces and bending moments to the burst pressures of corroded pipelines. It is revealed that the compressive axial force and the closing bending moment, causing compression in the corroded area, affect the burst pressure most significantly. Considering the axial compression and closing bending moment, failure loci of combined bending moments and internal pressures are developed for different axial forces. The developed failure loci can be used for assessing the burst pressure of corroded pipelines subjected to axial forces and bending moments. [ABSTRACT FROM AUTHOR]

The strength of pipeline with multiple corrosion patches depends on the number of corrosion patches within an area on the pipe surface, the locations of corrosion patches along the longitudinal and circumferential directions of the pipe. In this paper, the strength and deformation characteristics of corroded pipeline are investigated using finite element analysis. Pipes with different diameters and different depths of corrosion patches are considered. The spacing of the corrosion patches is varied along longitudinal, diagonal, and circumferential directions of the pipes. The study shows that the limiting spacing for interaction of corrosion patches depends predominantly on pipe wall thickness, corrosion depth, and the location of the defects. The diameter of the pipe has some influence on the interaction for large diameter pipes. A new interaction rule for the limiting spacing for interaction is developed for longitudinally spaced corrosion patches. For circumferentially spaced corrosion patches, the ASME recommendation for the limiting spacing is found to be reasonable. [ABSTRACT FROM AUTHOR]

The pipelines for oil and gas transportation are generally laid along a straight route to avoid the complexity of pipe bending. However, changing of pipe alignment is sometimes unavoidable where a straight pipeline is mechanically bent, or two straight pipelines are connecting using a suitable pipe bend/elbow. In this study, the burst pressure of corroded and uncorroded pipe bends was investigated using finite element analysis. The study shows that the pipe bend reduces the burst pressure that depends extensively on the radius of the bend. A parametric study was conducted to identify the parameters affecting the burst pressure of the pipe bend. The parameters investigated included bend radius, bend angle, pipe dimensions, corrosion dimensions, location of corrosion, and the grade of the steel. Corrosion at the intrados of the bend was found to have the most adverse effect on the burst pressure of bend for pipes with lower bend radii. The ratio of the burst pressure of the pipe bend to the burst pressure of corresponding straight pipes depends on the bend radius and steel grade and is almost independent of the pipe and corrosion dimensions. This ratio can be used to assess the burst pressure of a pipe bend using the burst pressure of the corresponding straight pipe. However, for a bend radius greater than three times the pipe diameter, the burst pressure of pipe bend is almost the same as the burst pressure of the corresponding straight pipe. • The burst pressures of intact and corroded pipe bends were investigated using finite element analysis. • Bend radius is found to affect the burst pressure more significantly than the bend angle. • Corrosion at the intrados position has the most adverse effect on the burst pressure. • The Burst pressure ratio can be used to calculate the burst pressure of pipe bend from the burst pressure of straight pipe. • Burst pressure model specific to steel grade should be used for the fitness-for-purpose assessment. [ABSTRACT FROM AUTHOR]