With the development of metallurgy and rolling technology, and the improvement of welding process, the fatigue behavior of modern pipeline steels may have changed greatly, but few fatigue test data has been achieved for the modern pipeline steels, which brings about many difficulties to the pipeline design and safety assessment. In this paper, a full-scale fatigue test is carried out to study not only the fatigue life but also the fatigue crack developing behavior. The study verifies and validates the reliability of small-size fatigue crack growth tests. Both fluctuation of operation pressure and transmission halt have obvious effect on the lifetime of the pipeline. When there exist flaws in the pipes, cyclic load caused by pressure fluctuation will promote the development of such defects especially as cracks. The full-scale fatigue test was performed on a X60 Spiral Submerged Arc-Welded pipe (Outside Diameter 660mm), which was pre-manufactured with a small outside surface crack-like flaw. The test result indicated that both defect size and cyclic load magnitude had great effect on crack propagation rate and fatigue lifetime. During the test, the artificial shallow surface defect developed only in the depth direction and finally caused the leakage. Comparison of test results between small-size and full-scale fatigue tests showed that small-size test can be used for lifetime prediction of the pipeline although there was some deviation.
Full-scale fatigue test on X60 spiral linepipe
Full-Scale-Dauerfestigkeitsprüfung einer spiralnahtgeschweißten X60-Rohrleitung
2006
7 Seiten, 10 Bilder, 3 Tabellen, 19 Quellen
Conference paper
English
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