Mohammad Hossein Sharifi - Faculty of marine science, Petroleum University of Technology, Mahmoudabad, Iran
Reza Soheili - Science and Research Branch, Islamic Azad University, Tehran, Iran
Ali Shaghaghi Moghaddam - Department of Mechanical Engineering, Islamic Azad University, Takestan Branch, Iran
Farhood Azarsina - Department of Marine structure, Science and Research Branch, Islamic Azad University Tehran, Iran

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 BS۷۹۱۰ guideline. Moreover, a comparison between these two methods is offered. It is concluded that, ECA by BS۷۹۱۰ 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.

Engineering Critical Assessment, Offshore Pipeline Girth weld, Surface Cracks, Acceptance Criteria, FEM