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

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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Link to publisher version (DOI)

10.1115/OMAE2018-78736

Link to publisher version (DOI)

10.1115/OMAE2018-78736