Large ocean-going vessels such as LNG carriers are moored to piers or jetties by substantial ropes. These ropes pass through a 'fairlead' as they leave the vessel to be tied off to a bollard on the pier. The two main classes of fairleads are Panama and roller fairleaders. A variety of ropes are employed over these fairleads, including six strand wire ropes and fibre ropes made from materials including HMPE (high modulus polyethylene), polyester, polypropylene and nylon. Steel wire ropes have recently been partially displaced by synthetic fibre ropes. Whilst more expensive, synthetic ropes are lighter and generally last longer than steel ropes, and thus promise cost effectiveness. Additionally, their light weight means that they are easier to handle which leads to savings on crewing costs; they cause fewer injuries; and, finally, cause less damage to the fairleader surface over which they operate. The paper presents results from a research programme to investigate the performance of wire rope and two types of HMPE fibre rope (with and without chafing protectors) on roller and Panama fairleads, and on a cast nylon material used as a bolt-on Panama liner specifically for use with fibre ropes. The loading regime to which the ropes were subjected in this series of tests was (by design) harsh, and was intended to simulate very severe wave induced vessel motions. The number of high load cycles in the full 1650 block loading is the equivalent of about 800 hours service. The following conclusions may be drawn from this work: 1. AmSteel-Blue and Steelite suffered rapid degradation when operating over a Panama fairlead either with chafing protection or without. 2. The chafing protection did give some benefit, but may merely have served to transfer the abrasion point from rope on Panama to rope on chafing protection (especially with AmSteel-Blue and MoorGuard). 3. The wire rope survived the 1650 cycles but suffered wear which would impact on the rope fatigue life. It also damaged the surface of the Panama, creating debris and a significant wear scar. 4. The nylon liner proved beneficial in protecting the fibre ropes from wear on the fixed Panama fairlead. 5. The AmSteel-Blue rope underwent the full 1650 cycles on the nylon liner, both with and without chafing protection. The peak temperatures were quite high (79 °C with no chafing protection) and the surface of the rope suffered some melding. 6. The Steelite rope without jacket on the nylon liner failed rapidly (after 311 cycles) from what appears to be accelerated creep rupture from elevated temperature. 7. The Steelite rope with chafing protection showed a dramatic improvement, and survived the 1650 cycles. 8. The temperature rise in the Steelite rope with chafing protection on nylon and steel Panama was very similar (37 °C compared with 36 °C). 9. All rope/chafing protection combinations performed well on the roller fairlead. 10. Where the rope does not cross the roller perpendicularly to the roller axis this can result in additional slip and wear of the rope. 11. Slip of the AmSteel-Blue within its relatively 'rough' chafing protector seems to have damaged the rope more than not having the chafing protector (compare results 9 and 10). 12. The temperature rise the rope suffers when operating on the roller is less than that on the Panama as the contact is rolling rather than fixed. 13. Although the temperature rise on the roller is lower than that of the nylon liner material, it is not thought that in either case the temperature rise would lead to a problem in service, where there is more opportunity for the rope to cool.


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    Titel :

    Wear of ropes on mooring fairleads


    Beteiligte:
    Ridge, I.M.L. (Autor:in) / Hobbs, R.E. (Autor:in) / Banfield, S.J. (Autor:in)


    Erscheinungsdatum :

    2011


    Format / Umfang :

    23 Seiten, 18 Bilder, 1 Tabelle, 2 Quellen



    Medientyp :

    Aufsatz (Konferenz)


    Format :

    Print


    Sprache :

    Englisch





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