This paper discusses the technical feasibility of applying internal friction damping (IFD) as a non destructive evaluation technique for synthetic ropes. Marine applications of interest for synthetic ropes include mooring lines and towing hawsers with specific emphasis in this paper on lines for single point moorings (SPM) in deep water ports (DWP). The theory of internal friction damping is briefly presented here as it has been historically applied to metallic materials. The paper then discusses the methodology for application of the IFD technique to synthetic rope material and construction. The experimental apparatus and specific laboratory technique are then discussed as applied to 6 and 8 inch circumference rope. Next, the paper discusses the experimental results and relates them to the feasibility of employing this technique as a monitoring method for the real world assessment of rope deterioration/performance. The characteristics of ropes when tested in both wet and dry conditions are discussed. A comparison of the effect of IFD to various synthetic rope failure mechanisms is presented. The paper concludes with specific conclusions and recommendations for further investigation into large synthetic rope testing and inspection for the ultimate potential development of this technique as a real time monitoring system for marine synthetic rope performance.--

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This paper discusses the technical feasibility of applying internal friction damping (IFD) as a nondestructive evaluation (NDE) technique to wire rope. The paper addresses the technical feasibility, laboratory testing on wire rope, and the associated test results on various samples of wire rope. These tests were eva1 uated in a series of laboratory experiments by measurint he internal friction damping during which several test parameters were changed. The test parameters including the tensile load, frequency of test load, exposure time of rope to load and variations in rope construction are discussed from the standpoint of IFD-NDE measurements.This paper discusses the methodology for applying the IFD technique to wire rope material and construction. The experimental apparatus and specific laboratory technique are then discussed as applied to different constructions of wire rope. Next, the paper discusses the experimental results and relates them to the feasibility of employing this technique as a method of monitoring for the real world assessment of wire rope deterioration in performance. The various rope construction characteristics as tested in dry conditions are discussed. Moreover, a comparison of the affect of IFD to wire rope fatigue load conditions is presented. The paper concludes with specific conclusions and recommendations for further investigation into large diameter wire rope testing and inspection for the ultimate potential development of this technique as a real time monitoring system for marine wire rope performance.

This paper presents design data for mooring hawsers for single-point moorings (SPM)-Properties of materials and constructions commonly used are discussed and compared. Factors that affect new and used hawser strength are discussed. Recommendations are made for SPM hawser material, construction, and safety factors for U.S. deepwater ports. Introduction During 1977, Exxon Research and Engineering Co. conducted a study for the U.S. Coast Guard to prepare guidelines for evaluating single-point moorings (SPM) for U.S. deepwater ports. As part of the study, SPM hawser systems were examined. This paper covers the major findings pertaining to hawsers.The hawser system serves to moor tankers to the SPM. An SPM hawser assembly consists of a large synthetic rope spliced to form eyes at both ends, or spliced end-to-end to form a loop, referred to as a strop. The eyes or ends of the strop are placed on thimbles, and chafing chains are attached to the thimbles. Flotation devices are provided to keep the chafing chains and hawsers afloat when a tanker is not moored. A typical SPM and hawser system with a moored tanker is shown in Fig. 1.Our examination of SPM hawser systems focused mainly on design. Information from many sources was gathered and analyzed in a comprehensive study of synthetic rope properties of interest in SPM hawser design. Data also was gathered for analyzing the associated hawser components, such as thimbles, flotation units, and chafing chains. Based on this study, guidelines were prepared for designing SPM hawser systems. Flory et al. presented a complete study of SPM hawser systems, along with studies on other aspects of SPM design. They included information on SPM hawser materials, constructions, breaking strengths, elasticities, safety factors, and assemblies. Supportive information presented here is not always complete. In some areas, we can give little more than conclusions and recommendations. Flory et al. give a more complete understanding of and more background to support our conclusions and recommendations. SPM Hawser Materials Nylon, polyester, and polypropylene synthetic fibers commonly are used for SPM hawsers. Other synthetic and natural rope fibers have properties detrimental for use in SPM'S. Fig. 2 gives comparative load-elongation curves for new nylon, polyester, and polypropylene ropes of the same construction. Table 1 shows comparative breaking strengths for large ropes made of each material.Fiber manufacturers often coat synthetic fibers to obtain desirable characteristics. Fibers of different coatings are differentiated by grade. Fibers used to manufacture rope are coated for maximum strength and to resist abrasion. Fiber manufacturers consider these fiber coatings proprietary, so it is difficult to compare the qualities of coatings used by different manufacturers. The characteristics imparted by the coating greatly influence the performance of an SPM hawser. Nylon Nylon is the most commonly used fiber for SPM hawsers. JPT P. 917

This paper presents design information for mooring hawsers for single point moorings. It is based on a recent study, conducted by Exxon Research and Engineering for the U.S. Coast Guard, which will serve as a guide for the evaluation of SPMs used at U.S. deepwater ports. Information from many sources has been drawn together and analyzed to present a comprehensive study of synthetic rope properties of interest in SPM design. Much of the information has not been published before. Properties of nylon, polypropylene, and polyester fibers, and the types of rope construction used at SPMs are discussed. The elasticities of ropes of various materials and constructions are compared. The methods which are used to rate large-rope breaking strengths are evaluated. Factors which affect new and used SPM hawser strength are discussed. Chafing chains, hawser floatation devices, and the methods by which hawsers are attached to the tanker are also discussed. Recommendations are made for SPM hawser material and construction. Factors of safety for SPM hawser design for U.S. deepwater ports are also recommended. These factors of safety are higher than those previously adopted by the industry. The data and findings presented in this paper will be of interest to SPM designers and operators and to other users of large-diameter synthetic rope. Introduction During 1977, Exxon Research and Engineering Company conducted a study for the U.S. Coast Guard to prepare guidelines for evaluating Single Point Moorings (SPMs) for U.S. Deepwater Ports. As part of the study, SPM hawser systems were examined, and this paper covers the major findings pertaining to hawsers. The hawser system serves to moor tankers to the SPM. An SPM hawser assembly consists of a large synthetic rope spliced to form eyes at both ends or end-to-end spliced to form a loop, referred to as a strop. The eyes or ends of the strop are placed on thimbles, and chafing chains are attached to the thimbles. Floatation devices are provided to keep the chafing chains and hawsers afloat when a tanker is not moored. A typical SPM and hawser system with a tanker moored is shown in Figure 1. The examination of SPM hawser systems focused mainly on their design. Information from many sources was drawn together and analyzed in a comprehensive study of synthetic rope properties of interest in SPM hawser design. Information was also gathered and analyzed on the associated hawser components, such as thimbles, floatation units, and chafing chains. Based on the study, guidelines were prepared for the design of SPM hawser systems. The complete study of SPM hawser systems, along with studies on other aspects of SPM design, is presented in "Guidelines For Deepwater Port Single Point Mooring Design" (l) available to the public through the National Technical Information Service, Springfield, Virginia 22151.