Hydrostatic Collapse Tests of Full-Scale Pipeline Specimens With Thickness Metal Loss

Abstract

The present paper deals with the subject of failure of deep-sea pipelines that have thickness metal-loss areas caused by corrosion and are subjected to high external hydrostatic pressure. An extensive research program was launched to observe failure modes, to examine existing and to develop prediction collapse equations, and to determine their accuracy. The program uses finite element modeling and external hydrostatic collapse tests of full-scale specimens. This paper presents and discusses the results of the first 20 collapse tests, which were performed in a new 103 MPa (15 ksi) hyperbaric chamber (760 mm internal diameter and 7200 mm length). The test results obtained with full scale specimens (324 mm external diameter and 23 mm thickness) made of low carbon steel API 5L X60 with external machined metal loss defects are used to verify the level of accuracy and conservatism of four analytical simple equations used to predict collapse of pipes with corrosion subjected to high external pressure.

Evaluation of the nominal thickness of pipelines using neural networks through the dispersion curves drawn with the SAFE method

“…There are several types of damage that can affect these structures, such as localized collapse due to buckling, caused by factory ovality aggravated during installation/operation [4], external pressure and internal pressure variations, the generation of a dent due to impacts with objects (such as the anchor or a piece of equipment dropped from a vessel operating in the area, for example) and detrition due to corrosion or erosion [5], [6].…”

Safe Design of Subsea Pipelines to Combined Seismic and Thermal Loading

“…Offshore pipelines and risers are employed for transport of hydrocarbons in deeper waters and harsher conditions (for instance, the deepest gas pipeline laid by Shell in the Stones field in the US Gulf of Mexico [2]). In such environments, thicker pipelines with the OD/t ratio as low as 10 are required due to the substantial hydrostatic pressure [3][4][5][6]. Moreover, the pipeline may need to be installed on seabed with escarpments that increases the risk of thermal buckling [7][8][9], free-spanning [10] and vortex-induced vibrations [11].…”