NDLI: Free-Span Flowlines Resistance to In-Service Fatigue Loading

Content Provider	The American Society of Mechanical Engineers (ASME) Digital Collection
Author	Iob, Francesco Mecozzi, Elisabetta Vito, Luigi Di Darcis, Philippe Marines-Garcia, Israel Hector, M. Quintanilla-Carmona
Copyright Year	2015
Abstract	Offshore petroleum fields frequently pass over areas with uneven seafloor. In such cases the pipeline may have free spans due to depressions crossing and are subjected to complex loading spectra. A major source for dynamic stresses in free span pipelines is vortex induced vibrations (VIV) caused by steady current since wave induced velocities and accelerations will decay with increasing water depth. The complex loading spectrum differs sensibly from the constant amplitude loading commonly adopted for qualification of the product (line pipe and its girth welds). Centro Sviluppo Materiali and Tenaris for some years are involved in the study of in-service variable amplitude fatigue loading of risers trough numerical calculations and comparison of the actual fatigue loading experienced by free span system with constant amplitude qualification typical loading. Two papers [1, 2] have been already presented in previous OMAE conferences. The present work reports a study dedicated to the free-span flow lines. The flow line analyzed is composed by OD 273.05 mm × WT 25.4 mm pipe lying on the uneven seabed. In particular the attention is focused on the analysis of VIV and its effect on fatigue life of the line. The Ormen Lange field, located at 120 km northwest of the Mid-Norway, was selected as reference scenario for the study. One of the most important factors influencing the pipeline response to the VIV is the free-span length. A sensitivity analysis about the influence of different parameters (free span length and fluid velocity) on system response and consequent fatigue damage has been performed. A case study has been selected among the cases considered in the sensitivity analysis, to produce the loading spectra to be considered in a laboratory fatigue testing campaign on strip specimens. The fatigue performance of these samples has been compared to analogous samples subjected to constant and variable amplitude loading available from previous works [1, 2] on riser systems (Steel catenary riser and Hybrid riser).
Sponsorship	Ocean, Offshore and Arctic Engineering Division
File Format	PDF
ISBN	9780791856529
DOI	10.1115/OMAE2015-42034
Volume Number	Volume 5B: Pipeline and Riser Technology
Conference Proceedings	ASME 2015 34th International Conference on Ocean, Offshore and Arctic Engineering
Language	English
Publisher Date	2015-05-31
Publisher Place	St. John’s, Newfoundland, Canada
Access Restriction	Subscribed
Subject Keyword	Water Strips Arches Pipelines Waves Welded joints Fluids Free spanning pipelines Risers (casting) Fatigue life Fatigue testing Sensitivity analysis Hybrid risers Fatigue Flow (dynamics) Seabed Petroleum Stress Vortex-induced vibration Pipeline risers Steel catenary risers Spectra (spectroscopy) Ocean engineering Pipes Fatigue damage
Content Type	Text
Resource Type	Article

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