Session: 03-03-06 Dent Assessment - Part III

Paper Number: 87360

87360 - A Comprehensive Fitness for Service Engineering Assessment of Gas Pipeline Dents 

Dents can be defined as a permanent deformation on the pipe wall, causing stress and strain concentrations and potentially resulting in crack initiation. Mechanical damages such as dents in buried pipelines are one of the most common threats to pipe structural integrity. Pipeline dents identified by in-line inspection tools need to be properly evaluated to determine its severity and threat to the existing pipelines. The present study provides a methodological framework to carry out a comprehensive fitness for service engineering assessment of dented natural gas pipelines using finite element analysis. Dent formation strain, brittle fracture, plastic collapse, local buckling, and pressure cycling fatigue failure modes are assessed. In addition, a rainflow counter, a fatigue calculator which is composed of a crack growth model, and a failure algorithm are developed to assess the performance of the dent against a pressure cycle over time. The remaining life of the dent based on fatigue damage accumulation is calculated not only using the analytical equations but also by performing an advanced strain-based finite element simulation using FE-SAFE commercial finite element software. A comprehensive parametric study on pipe size, dent shape, indenter size and shape etc. has also been conducted in the present study. The proposed fitness for service engineering assessment also addresses the susceptibility of dents to ductile crack and stress-corrosion cracking integrity threats that could develop due to the high membrane and bending stresses in the dented region. This methodology has been successfully utilized to assess in-line inspection dents found in an NPS 10 onshore natural gas pipeline. The results and the associated interpretations and discussions of the fitness for service assessment findings are presented herein. In summary, an advanced and comprehensive fitness for service engineering assessment framework based on the finite element analysis is proposed in the present study for dent assessment and failure prediction on pipelines.

Presenting Author: Suborno Debnath Northern crescent Inc.

Presenting Author Biography: Mr. Debnath has over four (4) years of cumulative experience (2 years of industrial and 2 years of research) in design and materials for pipelines, pipe support, cable support, steel building frame and steel warehouse. He has detailed knowledge and experience in fracture mechanics, buried pipeline stress analysis, pipeline defect analysis, and pipe-soil interaction.<br/>Mr. Debnath has an in-depth knowledge of API 579-1, ASME B31 pipelines codes, CSA Z662, and local regulations for Alberta, British Columbia, Saskatchewan, and Ontario.