Collapse resistance of thick-walled UOE linepipe for deepwater applications has been studied quite extensively over the past twenty years or so, culminating in a good understanding of the influence of UOE manufacturing processes on pipe geometry and material properties. To better understand the influence of these parameters on pipe collapse resistance, a test program was initiated by Nippon Steel Corporation at C-FER Technologies. Collapse tests are normally performed on pipe samples having a length-to-diameter (L/OD) ratio of at least 8, but this program focused on pipes having a L/OD ratio of 4.1 or less. Full-scale tests were performed on these short pipes and were compared to the results of companion pipes with an L/OD of at least 7.6. Integral in this program was the ability to design end closures that would minimize the influence of end conditions on pipe collapse. Thus, a rigorous finite element analysis (FEA) program was also undertaken to assist in the design of appropriate end closures for testing. This paper presents the results of all collapse tests and FEA, and shows that the analyses can generate correction factors for calculating the collapse strength of full-length pipes from short pipe test results.
The collapse strength of thick-walled UOE linepipe depends on many factors, including OD/t ratio, ovality and material stress-strain behaviour, including yield strength and stress-strain curve shape. Many of these parameters are driven by the manufacturing process of UOE pipe, including original plate manufacture and thermo-mechanical control processes, UOE pipe fabrication techniques and post-manufacture processes, such as thermal coating or stress relief.
To better understand and quantify the influence of these parameters on pipe collapse resistance, numerous experimental programs have been undertaken over the years.
Author: DeGeer, D., Piers, K., Timms, C., Xie, J., & Tsuru, E.
Publisher: The Sixteenth International Offshore and Polar Engineering Conference, 28 May-2 June, San Francisco, California, USA
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