Integrity assessment of pipelines exhibiting defects becomes more and more an issue in the oil and gas industry in particularbecause of field lifetime extension. Three levels of defects assessments can be distinguished:1 “Level 1” assessments are based on very simplified acceptance criteria such as a dent depth. They are veryconservative and their main advantage is to allow assessments in very short time period.2 “Level 2” assessments are based on analytical/empirical models supported by full scale testing. In principle, theycannot be used outside the conditions covered by full scale tests.3 “Level 3” assessments are based on advanced calculations such as finite elements. They allow reducingconservatisms but they need detailed material data and are, in general, very time consuming.The goal of “Empreinte” is to perform reasonably conservative “level 3” assessments in a very short time period (typicallywithin 48 hours from defect discovery to assessment).“Empreinte” is basically a pre and post processor to Abaqus finite element calculations. It was originally developed to assessthe integrity of pipelines exhibiting severe dents with taking into account that when a dent is discovered, the only availableinformation is, most of the time, the actual pipe geometry (defect profile and remaining wall thickness).The principle of “Empreinte” is to use the final pipe profile to design back a “virtual tool” from which the damaging processis modeled. Then, the burst strength of the damaged pipe is determined from finite element calculations. This actual burststrength is used to derive a safe operating pressure.“Empreinte” validation is supported by full scale tests in various conditions. It includes criteria to capture failure by plasticcollapse and by ductile fracture after significant damage development. “Empreinte” has been recently extended to theassessment of dents submitted to cyclic loading conditions using the Dang Van criterion.The enlargement of “Empreinte” validation tests database has to be a continuous effort. Updating materials data requirementsfor next pipeline projects is also a target.“Empreinte” has already been successfully used. “Empreinte” can be used for design purposes (risk assessments) or forintegrity assessments.
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