Abstract
The company DRC (pipe repair Department) located within the SONATRACH Company of oil and gas in Algeria, which is responsible for the repair of pipelines for the transport of gas or crude petroleum, will rehabilitate old pipes that have operated on-line for approximately 30 years or come from remaining projects. On the assumption that rehabilitating a pipeline means making it workable under the same conditions as a new structure and reducing the overall cost of the project. The abandonment of these tubes will have an important environmental and financial impact. The rehabilitation, which consists of recovering the maximum of tube, already used, therefore reduces the cost of the project. Inspection and evaluation of corrosion defects are carried out in accordance with ASME/31G method that is applied to low alloyed carbon steels with corrosion defects having soft profiles with low stress concentration. Our research will consist in developing a method using a behavior-damage coupling of the material to highlight the weaknesses of the ASME / B31G method and show for defects whose depth does not exceed 10%, these defects can survive hydrostatic testing but will develop during service when the pressure is variable.
Highlights
I n a pipeline project, steel represents more than 35% of the total cost; the rehabilitation, which consists of recovering the maximum of tube, already used, reduces the cost of the project
The ASME / B31G method [1] used by DRC / SONATRACH for the determination of the new operating pressure of a corroded pipe assumes that a pipe with a depth of corrosion defect not exceeding 10% of its thickness can be reused at the operating pressure without any risk and this regardless of the extension and the width of the corrosion defect
I n this study, a method was developed to highlight the weaknesses of the ASME / B31G method using the concept of damage mechanics
Summary
I n a pipeline project, steel represents more than 35% of the total cost; the rehabilitation, which consists of recovering the maximum of tube, already used, reduces the cost of the project. Metallurgical, and fractographic analyses as well as calculations using established ASME methodologies, Caligiuri has studied the rupture of natural gas pipeline in San Bruno, California [2] He observed that the failure was caused by the combination of a missing interior weld, a ductile tear, and fatigue cracking. They observed that the accelerated corrosion process applied to the specimens caused a not negligible reduction of the fatigue strength of joints These authors have studied the fatigue behaviour of a bolted connection with high strength bolts using finite element method in order to determine the fatigue life cycles of the studied joint. We have been able to model the corrosion of the X65 steel pipe taking into account the geometry of the defects, the boundary conditions and the mesh
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