PSI - Issue 60

Dhanesh N. et al. / Procedia Structural Integrity 60 (2024) 456–470 Dhanesh et al. / StructuralIntegrity Procedia 00 (2019) 000 – 000

469

14

Fig.16 shows the maximum stress range in the dented pipeline due to the peak pressure range (34 kg/cm 2 ). The resulting stress range due to internal pressure is significant, and hence the cumulative fatigue damage due to all identified cyclic pressure ranges is evaluated. For each pressure range, allowable cycles are estimated using the calculated stress range from the analysis and the S-N curve for Carbon steel from Annex 3F of ASME B&PV Code, Section VIII, Division 2 (2021), Part 5. Using estimated allowable fatigue cycles and the pressure cycle histogram, the fatigue damage at the end of 50 years of operational life is estimated. The estimated fatigue damage for the operational life of 50 years is significantly low (0.075 < 1.0) and has a significantly high fatigue life (666 years). Therefore, the pipeline segment with dent passes the fatigue damage criteria.

Fig.16. Stress range in dented pipeline due to peak pressure range (Inlet).

6. Conclusions In the present work, a case study on the integrity assessment of an in-service LPG pipeline with dent damage located at the highway crossing is presented. Since the dig verification of the dent was not feasible, a Level 3 integrity assessment of the pipeline as per Fitness-For-Service Standard API 579-1/ASME FFS-1 (2021) has been carried out. The novelty of the present work is that it considers all the possible vehicular load combinations as per Indian standards. The most critical vehicular load combination and its location which causes maximum stresses at the dent location are evaluated for the assessment. Nonlinear Finite Element Analysis (FEA) has been carried out to replicate the dent using general-purpose finite element software ABAQUS. The numerical replica of the dented pipeline segment was further assessed for potential failure modes. The integrity assessment shows the subject dented segment may not be a threat to the integrity of the pipeline with the present operating conditions and loadings. Accordingly, regular monitoring of the pipeline section operating parameters and anomalies (crack, metal loss, etc.) at the location of the dent is recommended to ensure its safe operation. The methodology presented in this work can act as a guide for the integrity assessment of pipelines with dent damage located at highway crossings. Acknowledgments The authors would like to acknowledge the support received from Engineers India Limited and thank the management for permission to publish this work. References API RP 1102. 2007. Steel Pipelines Crossing Railroads and Highways. American Petroleum Institute, Washington. API Specification 5L. 2013. Specification for Line Pipe-Upstream Segment, American Petroleum Institute, Washington, D.C. ASME Boiler and Pressure Vessel Code, Section VIII, Division 2, Alternative Rules. 2021. American Society of Mechanical Engineers, New York Belvereresi, C., Dann, M. R., 2017. Statistical Analysis of Failure Consequences for Oil and Gas Pipelines. Petroleum Science 7, 103-112. Cordell, J., Vanzant, H., 2003. The Pipeline Pigging Handbook. Clarion Technical Publishers and Scientific Surveys Ltd., Texas. Cosham, A., Hopkins, P., 2003. The Effect of Dents in Pipelines-Guidance in the Pipeline Defect Assessment Manual. Proceedings ICPVT-10, Vienna. ABAQUS. 2019. Analysis User's Manual, Dassault Systems. API 579-1/ASME FFS-1. 2021. Fitness-For-Service. American Petroleum Institute, Washington.