Predicting Hydrostatic Collapse of Pipes Using Finite Element Analysis

Abstract

A pipeline’s resistance to collapse is governed by geometric imperfections, material properties and residual stresses. The offshore pipeline design code DNV-OS-F101 provides a method for predicting collapse of pipelines with diameter to wall thickness (D/t) ratios between 15 and 45. This paper examined the various factors that could influence the collapse resistance of several pipe geometries, such as ovality, eccentricity, material stress-strain behavior and residual stresses in the hoop and longitudinal directions. A total of 132 cases were carried out, using 2D and 3D Nonlinear Finite Element Analysis, to predict the collapse pressure of several realistic pipe geometries. Results of this study suggest that the DNV-OS-F101 predictions are conservative and applicable for a wide range of D/t ratios. While there is close correlation between Finite Element prediction and DNV-OS-F101 prediction, there is a degree of conservatism at low D/t ratios using DNV-OS-F101 equations. Hence there would be scope for further optimization of pipe wall thickness design against the collapse limit state at low D/t ratios.

Casing structural integrity and failure modes in a range of well types - A review

“…However, Abdideh and Khah (2018) presents casing collapse phenomena as abnormal displacements of rock formations on the casing leading to collapse. Bastola et al (2014) examined the factors influencing pipe's collapse resistance and concluded that effects are small for 3D models with length to diameter (d/t) ratios above 10, and that an increase in initial ovality would lead to a decrease in the pipe's resistance to collapse. Salehi et al (2009) showed that reservoir compaction results in 4 different casing collapse mechanism; buckling, bending, traction and shear.…”

Collapse Analysis of ERW Pipe Based on Roll-Forming and Sizing Simulations

“…Collapse analysis was continued following the sizing analysis. For analysis, both ends of a section of pipe were fixed in all directions, and because the length of the pipe was 10 times longer than its diameter, the influence of the boundary conditions could be ignored in the center cross-section along the longitudinal direction of the pipe [5]. External pressure was applied uniformly to the outer surface of the pipe.…”

“…They also confirmed that the collapse performance could be improved by promoting the out-of-roundness phenomenon in cross-sections. Bastola et al [5] conducted finite element analysis and confirmed that residual stress could reduce the resistance to collapse pressure by as much as 20%, and that the residual stress along the circumferential direction of the pipe were more significant on collapse performance than those along the longitudinal direction.…”

“…As the demand for ERW pipe increases, higher accuracy in evaluating strength is now required to satisfy the design limit state, and one of the main considerations for the design of deep-water pipelines is to ensure resistance to external pressure. The collapse performance of a pipe against external pressure could be affected by factors that include material and geometric properties, as well as residual stress [5,6].…”

“…Thus, finite element analysis that can accurately simulate the manufacturing process is needed. The aforementioned studies [1,5,6], however, forcibly imposed such factors to their finite element model without simulating the manufacturing process, so that it is questionable whether the results can be considered realistic. Several studies [4,7,8] have investigated the effect of the manufacturing process on out-of-roundness or residual stress, but these studies did not simulate all steps in the manufacturing processes using a realistic material model.…”