Langeled: Pipe Capacity vs. Wall Thickness Selection

摘要

The Langeled Pipeline South (LPS) is characterized by a large diameter and thin steel wall, giving rise to an outer diameter-to-thickness ratio, D/t, larger than 45. The local buckling design equation in DNV OS F101 is explicitly defined as applicable to a pipe D/t ratio equal to or lower that 45. It was then necessary to investigate if DNV OS F101 could also be made applicable as a project guideline for D/t > 45. The scope of this paper is to present the results of a desk study carried out during the project development; the study aimed to verify the applicability of the local buckling design equations enclosed in DNV OS F101. In particular, the following aspects are discussed in the paper: Finite Element Modeling of the pipe section of the LPS, including weld misalignment and the specified geometric tolerances; 3-dimensional FE Models aiming to analyze the LPS under relevant load conditions; FE calculations and sensitivity analysis aiming to determine the nonlinear loading curve (moment vs. curvature under axial/pressure loads), and to identify the limit bending pipe capacity and the relevant deformations; comparison of the calculated limit bending capacity with the results from the application of the DNV OS F101 design format.