Heavy Denier High Performance Polyester Yarns for Deep Water Offshore Mooring Ropes

Abstract

Abstract Scope/Objectives: In order to meet the technical challenges of larger platforms in ultra-deep water (> 1500 meter), both mooring rope as well as yarn producers have to improve tenacity and modulus as compared with mooring systems developed for deep water (500-1500 m) since mid-1990's. The purpose of this study is to evaluate this new breed of High Modulus and High Tenacity polyester yarn. Methods, Procedures, Process 1. Yarn development: two of the largest global producers of industrial polyester yarns invested heavily in new production capacity and state-of-the-art polymer (LSP – Liquid State Polymerization) and multi-end spinning/drawing with Induction Godet duos with the advantage of using the same low cost raw materials of traditional industrial polyester yarn. The objective is to produce heavier denier yarns with superior tenacity and modulus with lower variability; 2. Rope construction development and sub-rope evaluation: the traditional method to make strands for a sub-rope uses a twisted multi-ply polyester yarn with a final titer of 40-100 thousand denier as a base. Recent development indicated that this rope construction is not effective since twisting yarn reduces rope tenacity and increase elongation at a specified load (reduce stiffness). Results, Observations, Conclusions: Guxiandao developed a HT/HM 3000 denier (G3014HQ) in 2011 with better mechanical properties than the traditional 2000 denier been used extensively the last 20 years. The characteristics of this yarn were used as a starting point for further yarn improvement with even higher tenacity, modulus in a heavier (6000 denier) put-up. Evaluation tests are performed on sub-ropes based on the conclusion from previous papers that mechanical properties of sub-ropes are highly correlated with test results from full size ropes. Sub-ropes of both 3000 and 6000 denier were produced with the same designed Breaking Strength at Lankhorst Brazil and Portugal. Novel/Additive Information: Similar sub-ropes produced using heavier denier showed a higher tenacity (+2%), reduce MBS test result variability and improved stiffness. Reducing the number of sub-ropes also increases the efficiency of rope making process and improve MBL. Using a heavier denier yarn is key to meet the future trend in mooring rope construction that uses larger sub-ropes. Considering stronger and stiffer ropes in mooring system design model could result in the reduction of the number of mooring lines required for a certain FPSO.