Vessel stability in polar low situations: case study for semi-submersible drilling rigs

摘要

The additional snow and ice loads that a typical sixth generation semi-submersible in polar lows may experience are estimated and the effects on the intact stability of the semi-submersible are analysed. The additional snow loads could be very significant if the snow accrete on all the horizontal surfaces of the semisubmersible, and could have more impact on the initial stability of the semi-submersible when in the survival from operating condition. Ice loads from sea spray icing may not exceed 300 tons in any of the semi-submersible loading conditions, except when the icing event extends to the main deck of the semisubmersible. The resulting asymmetric ice loads will lead to increase heeling of the semi-submersible, with maximum heeling occurring when the icing event extends to themain deck. Generally, the additional snow and ice loads in polar lows are deemed to represent operation and safety challenges.