A steel lazy wave riser for turret vs. Spread-moored FPSO in extreme and wave-induced fatigue conditions
Abstract
Here, the performance of a steel lazy-wave riser (SLWR) was numerically investigated and compared to a conventional steel catenary riser (SCR) for an internal turret and spread-moored FPSO in extreme 100-yr return and ambient metocean conditions. As expected, the SLWR demonstrated favourable characteristics by the elimination of local dynamic buckling in the touch down zone (TDZ) via a wave configuration that decouples surface-motion, hence significantly reducing the maximum stress and fatigue damage. Non-collinear waves and current in the oblique direction relative to the vessel heading showed amplified stress concentrations in the sag and hog sections as a response to the increased compressive (heave and pitch) vessel motions. Correspondingly, in the ultimate limit state, a SLWR showed similar stresses for both turret and spread-moored FPSOs. However, the turret-mounted SLWR demonstrated a less superior fatigue life compared to its midship-mounted, spread-moored counterpart, owing to riser hangoff location differences and correspondingly varied motions experienced by the riser.
Document Type
Conference Proceeding
Date of Publication
2018
Publisher
American Society of Mechanical Engineers
School
School of Engineering
RAS ID
29380
Copyright
subscription content
Comments
Szczepanski, D., Balash, C., & Martens, M. (2018, June). A Steel Lazy Wave Riser for Turret vs. Spread-Moored FPSO in Extreme and Wave-Induced Fatigue Conditions. In ASME 2018 37th International Conference on Ocean, Offshore and Arctic Engineering (pp. V005T04A078-V005T04A078). American Society of Mechanical Engineers.
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