The industry's recognized authority for design, engineering and application of equipment and services in the global ocean community
Issue link: http://sea-technology.epubxp.com/i/344822
Additional YoY abrasion tests were recently performed on presently avail- able nylon yarns. Two current yarn producers provided samples of their regular and marine-grade nylon yarns for testing. The marine-grade yarns performed signifcantly better than the regular yarns. Both marine-grade nylon yarns exceeded the earlier established CI performance criteria. As a result, CI fnally published the "Performance Requirements for Marine Grade Nylon Yarn for Fiber Rope," CI 2009N. The CI Technical Committee oper- ates on a consensus basis. Although a majority might be in favor of an action, if there are major objections, an effort is made to resolve the confict. Normally, CI cannot set standards or guidelines that exclude particular rope products, even those made by nonmember com- panies. In this case, a new category of product was being established that has special, superior, desirable properties. This allowed the Technical Committee to establish higher performance crite- ria that some products could not meet. The marine-grade nylon yarn crite- ria took more than 30 years to develop. The YoY abrasion test was frst devel- oped and demonstrated by OCIMF in the early 1980s. The CI effort to de- velop marine-grade yarn criteria began in the mid-1990s. During this period, several producers stopped making ma- rine-grade nylon yarn, but other pro- ducers have taken their place, so the guidelines remain relevant. Nylon fber is particularly affected by water. The nylon molecule absorbs water and swells, loses strength, and becomes less resistant to abrasion. A good marine-grade fnish protects the nylon fber from this effect. Thus a good marine-grade yarn is important for ropes used in marine service. We hope that the effort is worth it. We hope ship owners and other ma- rine operators will now realize ropes made of marine-grade yarn last much longer, and that they will specify ma- rine-grade nylon and polyester yarns in accordance with these CI guidelines to uphold safety in the industry. The CI standards and guidelines can be obtained from the Cordage Institute, www.ropecord.com. n ducers. Again, the marine-fnish rope performed best. OCIMF commissioned a university examination of the rope specimens after wet-cyclic load testing revealed that interstrand abrasion was the prin- cipal cause of strength reduction and rope failure. It was recognized that a test method was needed to quantify the yarn abrasion resistance of rope-mak- ing yarns. A yarn-on-yarn (YoY) abra- sion test method was then developed to compare yarn performance. OCIMF commissioned a university to evaluate the test method and compare the yarn performances. The good and improved marine-fnish nylon and polyester yarns were provided for blind testing. The results showed a correlation between the ropes that performed very well in wet cyclic tension and the yarns that performed very well in the wet YoY abrasion testing. The nylon yarn with the marine-grade fnish exhib- ited signifcantly improved resistance to wet yarn-on-yarn abrasion, and the marine-grade nylon rope exhibited sig- nifcantly improved wet cyclic load fa- tigue performance. The better-perform- ing polyester yarn correlated with the better-performing polyester rope. OCIMF incorporated the YoY abra- sion test into its "Guidelines for the Purchasing and Testing of SPM Haw- sers" in 2000. The YoY abrasion test was then published as a CI Standard Test Method in 2002. In the late 1990s, at the request of the United States Navy, CI set out to establish a defnition and guideline for marine-grade yarns for use in mooring and towing hawsers. Wet YoY abra- sion tests were performed on sam- ples of polyester and nylon yarns that claimed to be marine grade. All four polyester yarns exhibited very good performance. CI then published the "Performance Requirements of Marine Grade Polyester Yarn for Fiber Rope," CI 2009P. Three of the tested nylon yarns exhibited very good wet YoY abra- sion performance, but one performed relatively poorly. The producer of the poor-performing nylon yarn objected, and the draft nylon guideline was not approved at that time. John Flory is the president of Tension Technology Interna- tional LLC (Morris- town, New Jersey). He worked for Exxon Research and Engi- neering for 20 years, conducting research and development of mooring systems for tankers. He is a mem- ber of the Cordage Institute Technical Com- mittee and chair of the subcommittee that developed the marine-grade, rope-making yarn guidelines. I n the May 2002 issue of Sea Technolo- gy, I wrote a Soapbox entitled "Know the Ropes, Commodity or Quality," in which I said: "fber rope properties can vary greatly, depending on fber mate- rial, rope construction, and quality." I advised that "using the wrong type of rope or a poor-quality rope can result in accidents and fatalities." That article mentioned some of the standards and guidelines which were then available. At that time there were no guide- lines for yarn quality, making it diffcult for users to judge fber materials. It was not possible to specify fber quality, except by referencing a brand name, and many users cannot specify brand names. Now, the Cordage Institute (CI) has established guidelines for ny- lon and polyester marine-grade, rope- making yarns. The Oil Companies International Marine Forum (OCIMF) sponsored research in the early 1980s to deter- mine the causes of failure and develop guidelines for large single-point moor- ing (SPM) hawsers. Wet cyclic ten- sion testing was conducted on many different rope samples. A rope maker provided two nylon rope samples made of the same nylon yarn material from the same producer, one made with a good standard yarn and the other made with a new and improved marine-grade-fnish yarn. These two nylon rope samples were identical in yarn material and rope construction, except for the yarn fnish. The marine- fnish nylon rope performed much bet- ter than the other rope. Similarly, an- other rope maker provided otherwise identical polyester ropes made with polyester yarns from two different pro- soap box Setting new Industry Standards for Marine-Grade Yarns—John Flory www.sea-technology.com July 2014 / st 73