Reliability of the Installation and Operation of Pipeline Systems


Pipelines are one of the most convenient and effectiveways of transporting petrol over a long distance. The environmentapplies, beyond extremely high external pressures, lowtemperatures and intensive corrosive process, the occurrence ofdefects on the pipe body, which compromises the structuralintegrity of pipelines leading to catastrophic failures. The mainmodifications concern the mechanical resistance, toughness at lowtemperatures weld ability and resistance to embrittlement relatedto hydrogen. Among mechanical characteristics, the fracturetoughness is very important for pipeline steels in design and safeassessment. Aiming to enhance the reliability and operation ofcomplex pipelines system, a study based on the mechanics of theelastoplastic fracture in order to determine better prediction of thefatigue life. The materials tested here are API 5L X42 and X52micro alloyed steels, as well as to evidence the toughness resistanceof these materials. Results indicated that both X42 and X52 steelbehave in a similar way and in all cases a slight increase of thetransition temperature was found. The characteristic toughnessvalue shows an evident loss in mechanical performances ifcompared to the uncharged one.