This paper is concerned with the effect of internal corrosion or erosion defects on the collapse of pipelines under external pressure. Experiments are conducted on SS-304 tubes with D/t's of 21.0 and 18.7 with axially uniform grooves of several thicknesses and angular spans of 6 - 60 deg of angle. All specimens exhibited the classical ovalization mode of collapse with the grooved side being more deformed. For groove angles between 6 deg and 20 deg of angle the collapse pressure decreases as the angle increases but remains essentially constant for angles between 20 deg and 60 deg of angle. The collapse pressure was found to decrease with groove depth, reducing by nearly 50% when the groove depth reached 50% of the pipe wall thickness. The experiments were simulated numerically using both the custom computer code BEPTICO as well as an axially uniform finite element model. The predictions were found to follow closely the trends of the experimental results. The three dimensionality of grooves was examined using appropriate finite element models. It was found that grooves shorter than about 8D constitute local imperfections and accurate prediction of their effect on collapse pressure requires fully 3-D modeling. By contrast, grooves 10D long or longer behave essentially as 'long' grooves and can be analyzed using 2-D models.
Collapse of partially corroded or worn pipe under external pressure
Zusammenbruch teilkorrodierter oder abgenutzter Rohre durch äußeren Druck
International Journal of Mechanical Sciences ; 50 , 12 ; 1586-1597
2008
12 Seiten, 20 Quellen
Article (Journal)
English
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