Abstract

International audience; The safety of gas transportation pipelines under fatigue loading remains an important issue. The purpose of the present study is to better evaluate the fatigue crack growth (FCG) behavior by carrying out analysis/predictions and experiments in full-size pipeline steels. A full characterization was made using several samples of an X42 grade pipeline steel, to characterize the monotonic and the fatigue behavior. Fatigue tests on full-scale pipeline steels under pressure loading were performed. The potential drop (PD) method applied to pressurized pipes makes it possible to monitor and quantify both crack initiation and crack propagation. These tests served as a basis for numerical comparison. Crack propagation of the full-size pipeline steel was simulated by finit element analysis (FEA) using an adaptive re-meshing approach implemented as part of the Z-set/Zebulon software. Simulation allows predicting fatigue crack growth life on pipes using results of tests on specimens as an input.

Abstract

With global warming water issue is becoming a mean problem in areas of the south hemisphere where raining is decreasing considerably. As a result, preserving such resource is becoming a crucial task facing the authorities. One of the main ways of preservation is making the water pipelines network as safe as possible from any damages involving lose of water around urban areas in particular those situated within areas prone to seismicity. For this purpose, a method to assess the seismic vulnerability of water pipelines was developed and implemented in a Geographical Information System (GIS), allowing larger water supply network to be covered and studied. This method is based on the identification of the parameters that have an influence on the behaviour of pipelines. Each parameter having a coefficient that represent its influence on the behaviour of the structure, the product of these parameters represent the seismic vulnerability of the section pipe under study. As a result, a proposed classification is obtained allowing the determination of a safe section (green colour), an unsafe section (red colour) and an intermediate situation (orange colour). For a proposed application of the method, a case study for a town in suburb of Algiers is presented within this paper. It concerns the town of Blida. The results are given in the following sections.

Abstract

Due to external interference, pipelines used for onshore as well as offshore operations can present dent and gouge defects. As such defects can seriously impair facilities’ integrity and performance, it is necessary to evaluate the strains in the vicinity of these defects. The development of non-destructive approaches to assess defects severity remains an issue in the pipeline industry. In the present study, micro-hardness - strain relationships are established for three steel grades of pipeline materials: API X52 modern, API X52 vintage and API X63 vintage. The micro-hardness – strain correlations of the three pipe materials are analyzed in order to verify if they can be described by a master curve. For that purpose, Notched Tensile (NT) tests are performed in Longitudinal (L) and Transverse (T) directions for each grade in order to reach high strain values (up to 70%). The relationship proposed by Tabor was improved with the introduction of three new parameters that allow considering actual material behavior.