Publications
| Title | | Authors |
|---|---|
| Burst strength of gouges in low toughness gas transmission pipelines « back |
E Leveque, M Zarea, R Batisse and P Roovers |
| 15th Joint Technical Meeting, Orlando, Florida, May 2005 | |
| The “State-of-the-art review of the existing fitness-for-purpose assessment methods for damaged pipelines” [1] performed recently by Advantica identified, among others, the need to set a limit for the use of failure criteria for gouges and corrosion defects in the toughness-independent regime. This issue has very practical implications, as the length of older pipelines currently operated and having toughness values potentially leading to a toughness-dependent failure behaviour is not negligible. Therefore, their immediate replacement by new pipelines is not economically feasible, and there is a real incentive to be able to set the limit for the toughness-independent failure behaviour of gouges, as corrosion defects are handled by a parallel project led by PRCI. EPRG launched a project aimed at establishing a limit on the toughness value that separates toughness-dependent from toughness-independent failure behaviour. More specifically, one objective is to evaluate the toughness-dependent Battelle formula for burst resistance of gouges for (very) low toughness values. This mainly experimental project checks this behaviour on several gas transmission pipes, a small diameter one, 150 mm, a medium diameter one, 350 mm, and a large diameter one, 900 mm. Pipe material is carefully characterized in terms of tensile properties, Charpy energy, and shear area. Then, based on the toughness independent criterion, a set of gouges is defined, of different depths / lengths, so as to span the different regions of the criterion, covering both short and long defects. These defects are manufactured by spark erosion, resulting in thin slits. Each such slit is incorporated into a vessel that is submitted to a burst test, with a number of additional measurements, like strain gauges on the pipe surface, a clip gauge et the centre of the defect. For the small and medium sized pipes, temperature is also controlled during the test, to ensure it is as low as practically feasible, without heavy infrastructure. The results are interpreted both in terms of comparison with the criteria, and also in terms of analysis of the failure surface, to identify failure mechanisms. | |
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