Chain failure by bending on deepwater mooring systems

The premature rupture of mooring chains of the Girassol buoy after only a half-year of service was caused by bending fatigue of the first free chain link inside the chain hawse (foirlead). Although the mooring system had been designed according to offshore industry standards, it failed because of this bending-fatigue mode. A study of this bending phenomenon led to a redesign of both the top chain segment size and the hawse connection, which now includes a new chain-connecting arm (CCA). A new method was developed to estimate the fatigue damage in the chain subjected to bending, which was used to design a new CCA for the Girassol buoy.