Submarine Power Cable Bending Stiffness Testing Methodology
- Tiago Brun Coser (LAMEF, UFRGS) | Telmo Roberto Strohaecker (LAMEF, UFRGS) | Facundo Sebastiín López (Símeros) | Fabiano Bertoni (Símeros) | Howard Wang (ExxonMobil Production Company) | C. Blake Hebert (ExxonMobil Production Company) | Lauro Silveira (Kongsberg Oil & Gas Technologies) | Marco Vinicius dos Santos Paiva (Kongsberg Oil & Gas Technologies) | Paolo Maioli (Prysmian Group)
- Document ID
- International Society of Offshore and Polar Engineers
- The 26th International Ocean and Polar Engineering Conference, 26 June-2 July, Rhodes, Greece
- Publication Date
- Document Type
- Conference Paper
- 2016. International Society of Offshore and Polar Engineers
- Umbilical power cable, bending stiffness, full-scale testing
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- 43 since 2007
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As part of ExxonMobil OPSRB power cable qualification program, full-scale tests were performed on dynamic power cable samples in order to assess the bending stiffness. The test setup was developed in such a manner that allowed performing the bending test under different axial tensions. In general, incremental deflections were applied to the samples for a given axial tension in order to observe the layer slip mechanism, which is highly correlated to the flexural response. The bending stiffness was calculated before and after slip, and it was possible to observe that structure becomes much more compliant after slip occurs. All tests were repeated several times in order to get a consistent set of data. In many tests, it was possible to observe nonlinear behavior due to inter-layer interactions.
The paper will present the important findings that were achieved during the analysis of the tests results, especially the influence of axial tension. It was concluded that the axial tension has a remarkable impact on the bending stiffness. This was an extremely important finding, since the numerical model could not capture this non-linear behavior and can have a major impact on fatigue damage calculations during design phase. Also, it was possible to identify viscoelastic behavior of the cable due to the different polymeric components of the structure.
Submarine power cables play a vital role in offshore applications, being responsible for transmission of electric power from offshore platforms to subsea facilities. Basically, they are a flexible structure made up of different component layers and their main mechanical characteristic is that they are axially and torsionally stiff while being compliant when bent. This flexibility is achieved thanks to the fact that inner layers can slide one over another after a critical curvature is reached. Therefore, they are able to withstand large flexural deformations without failure (Brown, 2011; Vaz et al., 1998; Witz and Tan, 1992).
Depending on the application, umbilicals can either be designed for static or dynamic conditions. While static umbilicals mainly lie on the seabed after installation, dynamic umbilicals are used to connect floating platforms to subsea equipments, facing sometimes harsh environments and stringent performance conditions (Gjøsteen, 2011; Yasseri et al., 2014).
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