ABSTRACT

Recently, deepwater pipelines have been planned for transporting gas between continents. It describes the mechanical properties of the UOE pipe, estimates the collapse pressure, and considers the appropriate test procedures for measuring the collapse resistance more accurately. The results of this study clarify the optimum sampling position to measure the mechanical properties, the correction factor for the various conditions of the pipe collapse test, and the modeling methods for the numerical simulation.

INTRODUCTION

Deepwater projects for laying pipelines on the seabed have been investigated in Europe, Africa, and the Middle and Near East (Hillenbrand, Graef, Gross-Weege, Knauf, and Marewski, 2002). In these Projects, the collapse resistance of UOE pipe has been actively studied because the pipe size is designed with the collapse performance in mind. Some particularly useful data was published in the course of the Oman-India pipeline project, and it is apparent from their studies that the compressive yield stress in circumference (C-YS) governing the collapse resistance becomes lower than the material specification, and that heat treatment is useful for recovering C-YS (Stark and McKeehan, 1995, Al-Sharif and Preston, 1996). In these studies, numerical simulation techniques have been developed for predicting the collapse pressure. Kyriakides et al analyzed UOE pipe forming processes and the collapse behavior, and clarified the degradation of collapse pressure caused by the Bauschinger effect generated during the pipe forming process (Kyriakides and Corona, 1991). We as a pipe manufacturer had to come to grips with the collapse problem of UOE pipe to stabilize the collapse performance and supply reliable products. The objectives of this study are to determine the sampling procedure for evaluating the collapse pressure, to estimate the effect of test conditions on the resultant collapse pressure using the full-size pipe and to simplify the finite element model for predicting the collapse pressure.

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