The plastic collapse behavior of the pipelines with the different wall thickness and different strength was evaluated by using the finite element analyses. Joint designs of the API X65-API X80, API X42-API X65 and API X42-API X80 were employed to investigate the plastic collapse under tensile, internal pressure or bending load.
The wall thickness ratios of the pipe joint combinations with an outer diameter of 762 mm (30 inch) were 1.22, 1.54 and 1.89. End face of the pie joint with the different wall thickness was machined with a taper angle between 4° ∼ 45° along the longitudinal direction of the lower strength and thicker pipe.
A parametric study was shown that the tensile strength and moment of the pipe joint with the wall thickness ratio less than 1.5 were not influenced by the wall thickness ratio and taper angle; however those of the pipe joint with the wall thickness ratio more than 1.5 considerably decreased at the low taper angle. The failure pressure of the pipe joint with the different wall thickness was not influenced by the wall thickness ratio and taper angle.