Over the last several years there has been a substantial increase in the usage of polyester (PET) fibers for offshore mooring lines for oil drilling and production platforms. Although in-use experience with synthetic mooring lines has been favorable, there is an ongoing need for modeling the safety and reliability of these materials. However, reliability modeling of PET ropes has been hampered by the absence of a sufficient database of full-scale rope test data to use in model verification. An alternate methodology is to model the reliability of fiber ropes on a theoretical basis using the statistics of individual fiber physical properties coupled with knowledge of rope construction and translational efficiency. In this case it is necessary to understand the statistical variability of the basic strength member - the PET fiber. To aid in this approach the present study gives an overview of the basic statistics of PET fiber physical properties based on data from a typical PET fiber production facility. The basic processes of polyester fiber production and handling are reviewed as background, and typical testing protocols for fiber quality assurance are discussed. Representative data on fiber properties such as linear density, breaking strength, and elongation to failure are presented and variability within each group analyzed.
The use of polyester (PET) fiber mooring ropes has increased dramatically over the last several years. The majority of this growth has been in Brazil, where Petrobras has installed more than 10 units using polyester mooring spreads (Del Vecchio and Costa, 1999). Reduced system costs and simplified mooring scope are two reasons for the drive to replace wire ropes with PET. Several consensus documents such as the Engineered Design Guide (1999) and API RP 2SM (2000) have recently been developed to provide guidance on the use of synthetic ropes in mooring systems.
