Metals and Alloys Division Team N°83: Durability and Reliability of structures Project title : Lifetime and reliability of pipelines made of micro-alloyed steel (PLC X52 – X60 – X70) Project manager: ZELMATI Djamel Members: GHELLOUDJ Oualid, RICHI Wissem, HAZOURLI Hamza, AZZI Afeff Summary of the research project The transport of hydrocarbons by means of pipelines made of steel tubes remains the most economical and safest means, over long distances. However, the transport of gas under economic conditions requires the use of high transport pressures, and therefore the use of steels with a high elastic limit. These performance increases have been made possible thanks to research work, which has improved the mechanical characteristics and the toughness of pipe steels. During commissioning, pipelines undergo frequent inspections to identify potential degradation sites that may affect their lifespan. Unfortunately, like any engineering structure, pipelines are exposed to various dangers, and the risk of deterioration is imminent due to the aggressiveness of the environment, the vagaries of loading and the properties of the steels used. This project deals with the problem of the embrittlement of steel pipelines by hydrogen, and relates to the estimation of the remaining service life of a pipeline under fault of crack and localized corrosion, using on the one hand analytical methods and numerical methods. On the other hand, a static and dynamic experimental work, must be carried out in the first stage, to study the harmfulness of the defects on pipelines, and identification of the critical defects requiring a repair. Then, development of corrosion models of pipelines made of micro-alloyed steel (API X52, API X60, API X70). Afterwards, a methodology based on a deterministic and probabilistic approach must be developed in order to estimate the remaining life of a steel pipeline exposed to corrosion and crack attack, taking into account the geometry of the pipelines, the mechanical properties of the material, the applied loading, the correlations between the dimensions of the defects, and the distribution law of the corrosion rate.