Integrity increasing of damaged steel pipelines using external and internal reinforcing

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.