Green Water on Norwegian Production Ships

Green water events have made local damage on Norwegian production ships in sea states ignificantly ower than the 100-year sea states. These incidents have occurred both in the bow area, amidships and aft. Both analyses and model testing demonstrate a significant amount of green water on the deck structures in the 100-year wave situations. There is no general agreement on how to calculate the waves entering the deck of the ship, nor how well the wave height and the freeboard exeeedance are correlated. The model tests how a large scatter when relating reen water wave height and the corresponding freeboard exceedance. Significant modifications have been made on the production ships, such as raised forecastle and installation of wave-breaking walls. Operational restrictions have also been introduced, including restrictions to personnel access in green water zones and storage limitations. This paper describes the Norwegian requirements to air gap and green water. A description of the five production ships in Norway and the green water incidents are included. The status of the methods for evaluating the green water phenomenon as well as precautions taken to prevent further incidents, are also described