Materials and design of high strength pipelines

The demand for high-strength linepipe for offshore applications has increased considerably because of the challenges that the offshore pipelines should be contracted in ever-deeper waters and that for reasons of reducing operational costs pipelines should be operated at increased pressures. The development of new steels and improved pipe manufacturing capabilities enable high strength linepipe with appropriate toughness to be supplied. In this paper, the following subjects related to the use of high strength linepipe are discussed: Materials properties Evaluation of the use of high strength steel from design viewpoints; Assessment of loading conditions for installation and inservice conditions; Development of additional design criteria for the subjects not covered by codes, e.g. strength design of linepipes with yield anisotropy. The paper describes practical considerations on material properties, design loads,:code requirements and concludes with the developments in design criteria for strength design of high strength pipes with yield anisotropy.