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A new EMSA study recommends amending the damage stability requirements for passenger ships to account for new insights and improve ship survivability.
The damage stability of passenger ships is subject to the rules of the International Convention for the Safety of Life at Sea (SOLAS), which has been amended over the years to incorporate lessons learned and account for the availability of new technologies. The 1990 amendments introduced a probability concept for determining the damage stability of cargo ships, which was expanded to include passenger ships in the 2005/2006 amendments, commonly called SOLAS 2009.
A provision for the change to a probabilistic method was that it should not lead to stricter requirements. However, a number of sea incidents in recent years have raised questions about whether the requirements of SOLAS 2009 are sufficient to ensure the safety of passenger vessels, and several research projects supported by the EU have resulted in new recommendations for passenger ships. As part of these efforts, the European Maritime Safety Agency (EMSA) issued an invitation to tender a third study into possible enhancements of the survivability of passenger ships through improved damage stability (“EMSA III”). “A consortium coordinated by DNV GL was established,” reports Odd Karsten Olufsen, Senior Principal Engineer, Hydrodynamics and Stability at DNV GL. To incorporate the invaluable knowledge of the shipowning community and ensure broad support across the industry, the consortium included leading European passenger ship builders and designers, cruise and ferry operators, software developers, and academics (see infobox to the right). The consortium provided expertise in the fields of ship design, ship operation, risk modelling, formal safety assessments (FSA), accident data analysis, and software development. Design teams were formed to study ship survivability under flooding conditions, using specific sample ships chosen by the shipbuilders and operators. The engineering consultancy Safety at Sea (SaS) headed the investigations of risks from watertight doors, and NAPA Group, headquartered in Finland, developed the software for grounding calculations. The University of Trieste and the National Technical University of Athens carried out groundbreaking work on developing a new methodology for the assessment of groundings.
The joint EMSA III project studied risks resulting from collision, watertight doors, and grounding, and performed assessments of these categories as well as combinations of all three. An impact assessment based on EU guidelines was also part of the project. The study applied the methodology defined by the IMO guidelines for Formal Safety Assessment (FSA), which include hazard identification, risk analysis, the identification of risk control options, a cost versus benefit assessment, and the formulation of recommendations for decision-making. After evaluating accident records and risk escalation information from databases, the study groups defined a series of variants, or “Risk Control Options” (RCOs), for each of the six sampled ships to investigate the consequences of improved survivability in terms of cost. The study was limited to passenger vessels carrying a minimum of 400 persons. It was found that design variants with improved survivability in the case of collision accidents generally showed improved survivability in the case of grounding and contact accidents as well. The cost versus benefit analysis revealed that the cost of averting a fatality value (CAF) drops significantly when a combined assessment of collision and grounding is performed. The EMSA III research work resulted in a better understanding of the risks related to watertight doors and in software tools for grounding assessments. Based on the findings, a set of recommendations for updated damage stability requirements were drafted and forwarded to the IMO Sub-Committee on Ship Design and Construction (IMO SDC 3) for further consideration. After reconciling the levels suggested by the EMSA III study with alternative proposals from other flag states related in particular to smaller ships carrying up to 400 persons, SDC 3 developed a proposal which was submitted to the IMO Maritime Safety Committee (MSC) for approval.
Raising safety standards
The proposal implies stricter requirements regarding the survivability of passenger ships in the event of collision, raising the safety standards from current levels to reduce the risk involved in passenger transport at sea. Newbuilding and operational costs may increase somewhat as a result; however, this is justified by the cost versus benefit assessments performed by the EMSA III study, which is also a key element of the IMO FSA process. The impact assessment made in accordance with EU guidelines confirmed the conclusions of the study. “MSC96 approved the compromise draft amendments to SOLAS regulation II-1/6 in May 2016, and adoption will be discussed at the next MSC meeting (97) in November 2016,” says Olufsen. “At this point in time, the final outcome is still unclear, as some flag states may be in favour of changes, particularly regarding smaller ships.” The concerted effort of the industry consortium, which carried out the EMSA III study, has resulted in a proposal that is founded on the IMO FSA guidelines for use in the rule-making process and which was favourably reviewed by the IMO FSA Expert Group. “In addition to meeting the formal requirements, the expertise and knowledge of the leading ship designers/yards and operators that have contributed provide a solid basis for the decisionmaking at IMO,” says Olufsen.