Fibre rope deep water mooring: a practical model for the analysis of polyester mooring systems

The deployment of fibre rope moorings for deep water oil production systems was initiated in the late 80's, resulting in the installation, in 1997, of the PETROBRAS XIX semi-submersible Production Unit, the world-first polyester fibre rope taut leg mooring system. An important issue concerning fibre rope mooring systems is the load-elongation characteristics of polyester fibre ropes. As very limited data on full size ropes were available until recently, a joint co-operative study was initiated, in 1996, by a group of French Companies and Research Institutions, in order to acquire suitable engineering data by testing several full size ropes. Based on this work, presented elsewhere, a substantial improvement in the understanding of the load-elongation characteristics of Polyester fibre ropes has been possible, and a model was developed that, although not an 'exact' rheological model, represents nevertheless a significant advance over current practice. This model can be easily implemented in modern mooring analysis software. This paper presents the proposed model, the background information from which this model was derived, including comparisons with other published data, and with the data from full size tests of a number of ropes, resulting from rope Certification by Bureau Veritas. Some practical considerations for rope testing are also given. (author)