Validation of Power Cable Local Stress Analysis
- Marco Vinicius dos Santos Paiva (Kongsberg Oil & Gas Technologies) | Lauro Silveira (Kongsberg Oil & Gas Technologies) | Howard Wang (ExxonMobil Development Company) | C. Blake Hebert (ExxonMobil Development Company) | Tiago B. Coser (LAMEF – UFRGS) | Facundo S. López (Símeros) | Telmo R. Strohaecker (LAMEF – UFRGS) | Fabiano Bertoni (Símeros)
- 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
- Submarine power cable, local model, stress measurement results.
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During ExxonMobil Offshore Power System Reliability- B (OPSRB) qualification program, it was identified that the axial tension has a remarkable impact on the power cable bending stiffness which impacts installation loading. The test results also showed the viscoelastic behavior of the cable due to the different polymeric components of the structure. Also, it has been learned that the numerical model used for the power cable design could not capture such non-linear and viscoelastic behavior. This could have major impact on fatigue damage calculations during design phase. In conformity with test protocol, strain gauges were installed on a full scale power cable test specimen in order to validate the local analysis model. A series of loading combinations (tension and curvature) were imposed on the specimen to measure cable steel armour wire stresses. The measured stresses were then used to calibrate the tool to better predict the fatigue performance.
Submarine power cables were designed by Prysmian Powerlink on behalf of ExxonMobil OPSRB for dynamic operation on the fixed platform Harmony located in Santa Barbara Channel. In order to prove the cable integrity for the project application a series of tests were performed following a protocol written in accordance with ExxonMobil OPSRB requirements and lab (LAMEF) capabilities.
Kongsberg Oil and Gas Technologies was contracted to determine design operational loads through engineering analyses and Prysmian Powerlink responsible for providing design installation loads. The defined tensile values for both condition were used as input in the static tests which also included loads with contingency. The static tests performed for this qualification program were (i) torque balance and tensile test + pull-in head test; (ii) torsional stiffness and tensile test + hang-off test; (iii) bending stiffness test. The submarine power cable qualification program overall description and main findings can be found in Wang et al. (2016).
One of the main objectives of the static tests is to determine cable mechanical properties and validate a numerical local model developed by Kongsberg using the UFLEX2D software. This validation is important for the definition of stress ranges extracted from the model to build the dynamic full scale fatigue test load matrix. It is important also for the reassessment of global fatigue damage which is the full scale test target. Thus, the present work is focused on presenting a stress determination process and findings comparing test results with those predicted by the cable numerical model.
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