Fatigue Curves for Polyester Moorings
A state-of-the-art review
S Banfield, TTI, T Versavel, Noble Denton, RO Snell, BP Amoco, RV Ahilan, Noble Denton
The gathering momentum for the use of polyester ropes for long term production system moorings in deep water has instigated a thorough review of their fatigue performance. The traditional view of designers has been to use spiral strand steel wire rope T-N curves to assess the fatigue performance of polyester ropes on the basis that available evidence indicates that the latter's fatigue performance is superior to spiral strand wire rope. The authors have examined all the available fatigue testing data and the proposals for polyester specific T-N curves and have identified a number of issues pertinent to the derivation of fatigue design data for fibre ropes and propose an improved design curve.
This paper systematically identifies the various issues and proposes a rational way of including the available data (including run outs) for the development of a T-N curve for polyester ropes. The new data was used to re-visit the fatigue life and reliability for an example West of Shetland FPSO moored using polyester ropes (Ref.1).