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0 Possible steps to mitigate against this problem include:
(1) the use of torque balanced ropes as pendants and work wires;
(2) the use of low friction swivels (although there is a dearth of data on such devices and
furthermore the effect of cyclic rotation in permanent moorings has not been investigated);
and
(3) the avoidance of twist sensitive rope constructions as permanent mooring components.
0 More information is needed to facilitate accurate prediction of these interactions. This is
especially the case of chain and swivels. There is an understanding of the problem in the rope
fraternity (both wire and fibre) where it has long been recognised particularly in the context of
deep mine shafts, but experimental data for realistic rope sizes is not currently available.

Acknowledgement

The author acknowledges the invaluable input to this paper from discussions with engineers
employed by Petrobras in Brazil.

References

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