On the effect of corrosion defects on the collapse pressure of pipelines

Abstract

The loss of metal in a pipeline due to corrosion usually results in localized pits with various depths and irregular shapes on its external and internal surfaces. The effect of corrosion defects on the collapse pressure of offshore pipelines was studied through the combination of small-scale experiments with nonlinear numerical analyses based on the finite element method. After calibrated based on the experimental results, the model was used to determine the collapse pressure as a function of material and geometric parameters of different pipes and defects. An extensive parametric study using 2-D and 3-D numerical models was carried out encompassing different defect geometries and their interaction with pipe ovalization.

On the effect of narrow and long corrosion defects on the collapse pressure of pipelines

“…6. It is clear how the defect precipitates the U-mode of collapse, as observed previously by [13], and clearly depicted in Fig. 6(c).…”

“…A similar procedure to the one described in [13] was used to carry out the experimental tests on specimens with long and narrow defects. Schematic views of the apparatus are shown in Figs.…”

“…7. A detailed description of element types, boundary conditions, material constitutive model and pressurization scheme can be found in [12,13].…”

“…In other words, making the depth of the defect constant in the numerical model leads to a higher detrimental effect on the collapse pressure [13]. Nevertheless, actual corrosion defects can take any shape in both directions, depending on the corrosion mechanism.…”

“…The residual strength of pipelines with single corrosion defects was previously studied through a series of small-scale experiments and finite element analyses [12,13]. Two and threedimensional nonlinear finite element models were developed to predict the collapse pressure of intact and corroded pipes.…”