13th International Conference on Fracture June 16–21, 2013, Beijing, China Integrity increasing of damaged steel pipelines using external and internal reinforcing János Lukács1,*, Gyula Nagy1, Imre Török1 1 Department of Mechanical Engineering, University of Miskolc, H-3535 Miskolc-Egyetemváros, Hungary * Corresponding author: janos.lukacs@uni-miskolc.hu Abstract The integrity management and the lifetime assessment of different engineering structures and structural elements is one of the important technical-economic problems nowadays. The aim of the paper is to present the role of the external and internal reinforcing on the structural integrity of transporting steel pipelines, based on own experimental investigations. On the one hand, external and internal reinforcement technologies were developed using carbon fibre reinforced polymer matrix composite (CFR PMC) and glass fibre reinforced polymer matrix composite (GFR PMC), respectively. On the other hand, known external technology was used for the reinforcing of girth welds. Fatigue and burst tests were performed on large pipeline sections containing natural and artificial metal loss defects, and girth welds including weld defects (passed and not passed quality). Burst tests were executed after fatigue tests, using 20.000 or 100.000 cycles. Different corrosion defects were tested as natural defects, and longitudinal and circumferential gouges as well as holes and through holes were investigated as artificial defects. Both unreinforced and reinforced pipeline sections were examined. The applicability of the hybrid structures (steel + polymer matrix composites) were demonstrated by means of the experimental results and defined safety factor. Keywords pipeline, reinforcing, structural integrity, PMC, burst test 1. Introduction The treatment of the degradation and failure of different engineering structures, structural elements and equipment, the management of their lifetime is one of the important technical and economic problems of nowadays [1]. The cause of it is unambiguous: on the one hand, significant part of the structures have already reached or exceeded their originally planned lifetime [2], accordingly their following operation is a general interest; on the other hand, the safe and economic operation of the new structures is a key-question. The experiences of the operation [3], the frequency data of fractures, and the different failure statistics [4-6] of the engineering structures having great importance show, that the significance of cyclic loadings, fatigue and fatigue crack propagation is emphasized in general. Among the engineering structures, hydro-carbon transporting pipelines fill an important part. Approximately, the half of the total length of the Hungarian gas transporting system is over 30 years. In the technical requirements for the pipelines, the estimated lifetime was 30 years in the 1970’s [7]. However, as the pipeline age is over 30 years, a sharp increase can be experienced in the probability of failures, according to the “bath tub” failure curve [8]. Therefore, the first global aim of our research work is to improving the integrity of the Hungarian natural gas transmission system. Material databases play important role both on the integrity management and on the Engineering Critical Assessment (ECA) of the pipeline systems. Therefore, the second global aim of our research work is to establish a Pipeline Integrity Management System (PIMS) with different data, frequently with experimental data. Material databases collected for general or special purposes and the synergy among the databases can be used to increase the efficiency of the user decisions and the reliability of the lifetime estimation. Different databases were developed for managing different pipeline systems. Data found in standards, in rules, in prescriptions and measured values were integrated in the databases. Additional databases were developed for design calculations and numerical analysis, including physical and plasticity constants of steels, polymers and Polymer Matrix Composites -1-
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