Collapse Testing and Analysis of High Frequency Welded (HFW) Steel Pipes

Abstract Among many factors affecting the collapse limit of pipelines, the line pipe fabrication process has the strongest impact. The present study examines the collapse resistance of pipes fabricated by the High Frequency Welding (HFW) method and focuses on quantifying the effects of heat treatment with respect to the collapse limit of this class of cold formed pipes. The research is carried out for the case of two HFW line pipe specimens with 16 inch outer diameter (Do), 19.1 mm wall thickness (WT) and length equal to 17 times the outer pipe diameter (17Do). One of the HFW pipes has been coated prior to testing (“heat treated” pipe), while the other pipe remained bare (“as fabricated” pipe). Both pipe specimens were subjected to full-scale collapse in a large external pressure testing chamber to determine the collapse pressure and the propagation pressure of both pipes. The full-scale tests are simulated using advanced finite element (FE) tools, considering the actual material properties/geometry of each pipe before full-scale tests. The numerical predictions of the collapse pressure and propagation pressure are in a very good agreement with the experimental ones, while the FE models are also capable to predict the enhanced collapse pressure after coating.