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1- Faculty of marine science, Petroleum University of Technology, Mahmoudabad, Iran
2- Science and Research Branch, Islamic Azad University, Tehran, Iran
3- Department of Mechanical Engineering, Islamic Azad University, Takestan Branch, Iran
4- Department of Marine structure, Science and Research Branch, Islamic Azad University Tehran, Iran
Abstract:   (4684 Views)
Economical design with sufficient fracture resistance is of high importance in any offshore pipeline projects. Using an Engineering Critical Assessment (ECA), alternate acceptance criteria for pipeline girth weld inspection can significantly reduce the cost of constructing of offshore oil and gas pipeline by minimizing unnecessary repairs. Offshore pipelines consist of short pipeline segments connected by girth welding method. Surface and embedded elliptical cracks due to welding operation are often observed at welding zone which pose a potential threat to the reliability of the offshore pipelines. To derive the acceptance criteria for pipeline girth weld defects and pipeline safety during installation and operation phase, an ECA based on fracture mechanics is required. In this paper, ECA of offshore pipeline with semi elliptical surface crack under pure tension loading is performed according to finite element method and BS7910 guideline. Moreover, a comparison between these two methods is offered. It is concluded that, ECA by BS7910 guideline is more conservative than finite element method, and the difference between the two diagrams increases as strain levels are increased. Also, comparisons of critical crack size curve for various strain levels are studied.
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Type of Study: Research Paper | Subject: Offshore Structure
Received: 2018/03/14 | Accepted: 2018/09/2

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