Numerical Modelling of Crack Behaviour in Buried Pipes

Pipelines provide a critical function to the stability of chemical plant operations and transportation of fluids. The requirement for sound design and fabrication, inline inspections and maintenance are critical to reduce the risk of failure due to pre-existing or newly developed defects. Cracks can significantly impact the integrity of pipelines thus advanced inspection technologies, such as inline inspections, are important to identify the severity of the defect and implement an appropriate remediation action. Cracks act as stress concentration points from which the failure tends to initiate. Process upsets; such as pressure fluctuation, can cause a variation in the hoop stress levels, driving force for fatigue crack growth, which can lead to failure causing loss of containment, fires, or explosions. Existing cracks should be characterized to estimate residual life and hence safe operation based on the approach of damage tolerance. Currently, there is limited knowledge on the behaviour of cracks that develop in buried pipes. The geometry and orientation of these defects, operating conditions, external loading, and material properties affect the intensity of the propagation and arrest of cracks. Hence, an investigation into the behaviours of cracks with the intent to provide the basis for the development of an engineering critical assessment (ECA) is relevant.