Marine winterization - Measures to abate sea-spray icing

Abstract

<p>This thesis includes the topic of sea-spray icing on vessels and structures and dives further into methods of ice management. Sea-spray icing is a challenge in cold waters, particularly for small and mid-sized vessels. Excessive ice accretion is hazardous for vessel stability, operations and personnel safety. <p>Sea-spray icing from wave-vessel-wind interaction is a complex phenomenon. No measuring technique currently exists to fully capture the distribution of the incoming water flux over a moving vessel. Measuring the incoming flux as the fluid simultaneously undergoes a solidification process, adds even more challenges. Some records of the resulting ice thickness occur, but the research field generally lacks data. Creating tools to predict ice accumulation is a developing field of study, where tools e.g. computational fluid dynamics and machine learning have potential. Experimental data is crucial for model verification, and this thesis contributes with a comprehensive parameter study under laboratory conditions that could support further development of prediction models. <p>Data from the parameter study was extended to investigate the threshold between melting and freezing. When the thermal capacity of the incoming water flux exceeds the freezing capacity of the existing ice or substrate, melting occurs. This threshold became a key principle for investigating an alternative way to mitigate ice accretion, deicing with flushing seawater. <p>Implementing the Polar Code in the SOLAS Convention 2017 was a great international step towards increasing the safety of vessels sailing in polar waters. The code requires an operational risk assessment, and the individual vessel is obliged to carry systems for i.e., ice removal that meet the requirements. The function-based requirements in the Polar Code detail end goals, but do not generally instruct how the goals should be met. Multiple methods for deicing and anti-icing are needed. Resource scarcity, like electricity and personnel, limits current solutions, and a larger toolbox at our disposal can increase flexibility, environmental performance, efficiency and safety. <p>Experiments were carried out to determine if flushing seawater could be a tool against accumulated sea-spray ice. Using seawater is not common practice, and this thesis is, therefore, a first approach to evaluate the method. Full-scale tests of deicing with seawater were performed on vessels and structures in varying meteorological conditions typical of larger parts of the Barents Sea. Seawater is an abundant resource, and the preliminary test from this thesis shows that utilizing seawater should be explored as a deicing and/or anti-icing method. Further work should include expanding the tested operating range and surface area, with distribution systems designed specifically for this purpose.