TfdS paper was selected for presemtatlonby the OTC Program Committee followingreview of informationcontainedin an absIract submittedby the auihor(s). Contenis of the P*er, w prosonted,have not bee" reviewed by the Offshore TechnologyConference and am subject to mrrectlon by the author(s).The material, = presented, does not necessarilyref!eã ny positionof the OffshoreTechnologyConference or Its officers.Permissionto copy1srestrictedto an abstractof not more than 3W words. mustrations maY WJlbe u@ed. me abstract should contain$msplcuous acknow!edgmantof where and by whom the papar Is presented. ABSTRACTFive years of operating experience with a floating production system mooring are described. Irr-service chain diameter measurements and cathodic protection levels are described.Detaiied examination of removed components shows that wire ropes in a permanent mooring system degrade differently from those on a mobile unit and that careful consideration should be given to minimisirrg installation damage. Break testing of 84mm ground wires after five years service reveals a loss of strength of only 0.1% to 0.2% per year. Strength reductions of 1.5% to 2% per year are noted for the winch wires. In this case, the fairleader sections of the winch wires have suffered less damage than the winch sections. Chain breaking strength data is presented showing that used f02mm Grade 3 chain from the mooring consistently sustained loads some 13% higher than the catalogue breaking strength of new chain. References,nomenclature, Iables and figures al end of paperBecause of the large number of lines, the 100 year return environmental design basis and the high factors of safety, the Af-fOOl mooring system is arguably one of the most robust currently in operation in the North Sea. This paper brings together the original design assumptions for the mooring components, the subsea inspection data, and the results from the testing of removed components. Operational HistoryMooring system performance has generally been good. In particular, the vessel excursion and line tensions are lower than predicted. However, although no line failures have resulted from overstressing, fatigue damage, or corrosion, the AHOOfhas lost a mooring line on two separate occasions.On both occasions, approval was gained from the Certifying Authority to resume and continue production operations with revised operational criteria appropriate to an eleven line system. On neither occasion was the revised operational criteria exceeded.The first incident was due to failure of the bolted connection at the bottom bearing mounting on the line 1 fairleader. The fairleader then detached from the column foundation structure and parted the winch wire.Extensive investigations were conducted to determine the cause of failure, and to assure the integrity of all other components involved. It was concluded that the failure was due to the original bolts being of inadequate section and ductility. The integrity of the mooring system was restored to design levels by correcting these defects.The...
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