Synthetic mooring ropes for marine renewable energy applications

Weller, Sam; Johanning, Lars; Davies, Peter; Banfield, S.J.

doi:10.1016/j.renene.2015.03.058

Cited by 102 publications

(62 citation statements)

References 45 publications

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“…Under some conditions polyester ropes, which are favoured for offshore platform station-keeping, are too stiff for wind turbine moorings, and polyamide may be a suitable alternative. While early studies on fatigue of braided nylon ropes showed very short lifetimes some recent results have indicated that it is possible to significantly enhance lifetime by modifying rope construction and improving fibre coatings [1]. The fatigue results presented here for ropes from a different supplier, confirm this result.…”

supporting

confidence: 79%

“…Since these applications aim at harnessing marine energies, the systems are located on exposed area where dynamic loading are significant. In addition, the inherent moderate to small water depth induce a global stiff behaviour of the mooring system in using standard components as per done for deepwater floating oil platforms [1] (steel chains or polyester rope).…”

Section: Introductionmentioning

confidence: 99%

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Fatigue of polyamide mooring ropes for floating wind turbines

et al. 2018

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Abstract. This paper describes a study of the fatigue characterization of polyamide mooring ropes for floating wind turbines. Under some conditions polyester ropes, which are favoured for offshore platform station-keeping, are too stiff for wind turbine moorings, and polyamide may be a suitable alternative. While early studies on fatigue of braided nylon ropes showed very short lifetimes some recent results have indicated that it is possible to significantly enhance lifetime by modifying rope construction and improving fibre coatings [1]. The fatigue results presented here for ropes from a different supplier, confirm this result. In order to develop an accelerated evaluation of the fatigue performance, heat build-up tests have been performed, and promising first results are shown. Finally, the influence of coating is examined by microscopy and yarn-on-yarn tests, in order to improve understanding of the fatigue mechanisms leading to failure. IntroductionAs the development of Marine Energy Converter systems (such as wave energy generators, tidal current turbines and floating wind turbines) starts to flourish, there is a need for mooring lines in shallow water (between 50 and 100 m). Since these applications aim at harnessing marine energies, the systems are located on exposed area where dynamic loading are significant. In addition, the inherent moderate to small water depth induce a global stiff behaviour of the mooring system in using standard components as per done for deepwater floating oil platforms [1] (steel chains or polyester rope).The system integrity will be maintained by damping the dynamic loadings, so requiring the use of more stretchable fibre ropes than polyester. also examined a nylon rope which had been tested at sea for 18 months on a wave energy buoy, and showed the importance of loading history and operating conditions on nylon performance.The idea of using long term mooring lines in this material is relatively new, and there is little knowledge on the durability behaviour of such structures. It is therefore crucial to further investigate the behaviour of polyamide mooring ropes, in order to optimise their utilisation.The database is still very limited, only the paper by Ridge et al provides long lay length stranded PA rope fatigue results [3]. Thus the deployment of these fibres for permanent mooring is currently impossible due to the lack of data on their long term mechanical properties.The goals of the present study are therefore to provide a better understanding of the mechanical behaviour and the fatigue damage of these polyamide ropes, in order to help designing floating wind turbine mooring lines. However, fatigue studies are quite long and costly, this is why an evaluation of rapid characterization by heat build-up measurements [5] [6] has been included in the test programme. This kind of test has proven to be efficient on a wide range of materials [7]. These techniques have been developed and successfully applied in recent years to various polymeric materials included polyamide, from ...

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supporting

confidence: 79%

Section: Introductionmentioning

confidence: 99%

Fatigue of polyamide mooring ropes for floating wind turbines

et al. 2018

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“…Steel mooring components such as chains and stranded wire ropes are used exclusively. Synthetic fiber ropes can potentially be applied to develop cost-effective designs for the mooring systems of marine renewable energy devices [10]. The material of the mooring line for our ocean-current turbine should be synthetic rope.…”

Section: Mooring Systemmentioning

confidence: 99%

Scale-Model Experiments for the Surface Wave Influence on a Submerged Floating Ocean-Current Turbine

Shirasawa¹,

Minami²,

Shintake³

2017

Energies

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Abstract:In order to harness the kinetic energy of marine currents, we propose a novel ocean-current turbine with a horizontal axis. The turbine can be moored to the seabed and function similarly to kites in a water flow. To operate such turbines in a marine current, the resulting rotor torque needs to be canceled. Therefore, the proposed turbine is designed with a float at its top and a counterweight at its bottom. Thus far, we have verified the turbine stability and blade performance through towing experiments. As the next step, we constructed a scale-model turbine to confirm the mooring system. This experiment was performed at a circulating water channel with wave-making facilities. The influence of waves on the floating body was also investigated. In this paper, we report the behavior of the scale-model turbine moored to the tank bottom and discuss the influence of surface waves.

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“…The use of synthetic fibre ropes for mooring systems has seen a sudden rise in marine applications over the last two decades [5] albeit mainly for deep water mooring [6]. Experience and feedback from the use of polyester ropes for MRE device moorings is still limited in terms of publications produced.…”

Section: Introductionmentioning

confidence: 99%

Abrasion process between a fibre mooring line and a corroded steel element during the transit and commissioning of a marine renewable energy device

Herduin

Banfield²,

Weller

et al. 2016

Engineering Failure Analysis

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SummaryThis paper brings together two experiences from TTI (Tension Technology International) and the UoE (University of Exeter) and aims to quantify the damage that could be experienced by fibre mooring lines during the transit and commissioning phase of Marine Renewable Energy (MRE) devices.1. While deploying a new prototype of anchoring system for a MRE device, UoE experienced the failure of a new polyester mooring line during transit to site (90 minute duration). A thorough visual inspection supported by Scanning Electron Macroscopy (SEM) analysis and tensile test have established the physical conditions of the fibre rope before its failure.2. Wear testing led by TTI has investigated and established a relation between the degree of abrasion sustained and the residual strength of Dyneema ® fibre ropes. The ropes were submitted to friction forces via cycling over a roller and a fairlead with different abrasive surfaces (from 7.6 to 254.3μm). Negligible wear occurred with the low roughness surfaces and very high wear at the higher roughness surfaces.The load experienced by the polyester line during the deployment of the anchoring system was simulated with the software OrcaFlex TM . Dynamic modelling using representative conditions indicates that the polyester mooring line was loaded between 3 and 20% of its Minimum Breaking Load (MBL) which is well below the design load of the rope. IntroductionTo date there are only a few MRE designs which have achieved a pre-commercial development status. Experience in deploying such devices and specific guidance are missing. The approach of designers is thus conservative and based on the offshore oil and gas industry and anecdotal evidence [4].The use of synthetic fibre ropes for mooring systems has seen a sudden rise in marine applications over the last two decades [5] albeit mainly for deep water mooring [6]. Experience and feedback from the use of polyester ropes for MRE device moorings is still limited in terms of publications produced. This paper focuses on the commissioning phases of MRE devices, with a specific focus on the deployment of a novel anchoring system. Handling, lifting and rigging of mooring lines could result in damage during transport or installation as discussed in [7] and [8]. The strength of a rope will inevitably degrade from mishandling. Several research programs have been carried out to investigate the abrasion and twisting damage by rope manufacturers for towing systems. For example incorrect handling during transport could cause significant damage to the rope due to abrasion and the application of sudden high loads is one of the most severe conditions that a rope can experience [9].Certification standards and specific test methods have been developed to test the abrasion resistance of yarns [10] - [11]. The abrasion mechanism was described in [12] as a sequence of fibre peeling induced by surface shear forces. However the abrasion resistance of a fibre rope is not determined by standards and knowledge is only based on empirical test data.The exte...

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Synthetic mooring ropes for marine renewable energy applications

Cited by 102 publications

References 45 publications

Fatigue of polyamide mooring ropes for floating wind turbines

Fatigue of polyamide mooring ropes for floating wind turbines

Scale-Model Experiments for the Surface Wave Influence on a Submerged Floating Ocean-Current Turbine

Abrasion process between a fibre mooring line and a corroded steel element during the transit and commissioning of a marine renewable energy device

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