Novel Prediction Model of Tensile Strain Capacity for Pipelines with Corrosion Defects

Abstract

Accurate prediction of tensile strain capacity (TSC) is the key to the strain-based design and assessment (SBDA) of buried pipelines. Various TSC prediction models proposed by research institutions such as the Pipeline Research Council International (PRCI) and the Center for Reliable Energy Systems (CRES) are not applicable to pipelines with corrosion defects. In view of this, this study proposed a new TSC prediction model for corroded pipes based on extensive parametric finite-element analysis (FEA) validated by full-size pipe (FSP) tensile tests. In the proposed model, the corrosion defects were assumed to be a curved boxed shape. Based on the dependence of the TSC on the input parameters, the model considered the combined effect of material properties and internal pressure on TSC and employed a defect geometry factor function based on the corrosion defect depth, width, and length. The accuracy and reliability of the proposed method were validated by extensive parametric FEA and error analysis. The results showed that the method can be applied to the practical safety assessment of corroded pipelines in strain-based design guidelines. Assessing the safety of pipelines by axial strain can solve the problem that it is difficult to monitor the complex strain state of the pipe body under ground movements. Tensile strain capacity is an element to assess the tensile resistance of buried pipes to fracture. This study developed a tensile strain capacity prediction model for corroded pipes, which is faster to calculate compared to existing evaluation methods. When corrosion anomalies are discovered in areas with ground movement hazards, the proposed model can be used to quickly estimate the tensile strain capacity of the pipeline to make contingency measures. When the evaluated corroded pipe still has sufficient serviceability, the strain monitoring equipment can be used to monitor the remote strain of the pipeline in real time, which needs to be guaranteed to be less than the tensile strain capacity to fully utilize the pipeline performance. The work in this study can provide a reference for strain-based assessment and design of corroded pipes.