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HANSA 12-2019

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Schiffstechnik | Ship

Schiffstechnik | Ship Technology Guest contribution Hayato Suga – ClassNK A progress report on class rules for LNG, hydrogen and other alternative energy sources As the conversation on alternative fuels continues to unfold ClassNK is focusing on updating the rules that will ensure fast-emerging industry requirements meet safety imperatives, as well as the longer-term research needed to reconcile vessel operations with shipping’s lower-carbon future. Today, LNG represents a central strand in ClassNK rule development, both as a cargo and as ship fuel. The global LNG carrier fleet currently comprises some 600 ships and is expanding. In Japan, the major yards such as Mitsubishi, Japan Marine United (JMU) and Kawasaki are working on newbuilds, while their Korean and Chinese counterparts have an expanding orderbook. What this aggregate statistic doesn’t reveal is a structural shift in the fleet. Traditionally LNG carriers were placed on long-standing charters to support projects between a major energy supplier and set customers. Recently, however, new players are joining the market to satisfy emerging demand in small-scale LNG distribution to pockets of stranded demand and in bunkering LNG as a marine fuel. As these new entrants typically have less experience than established carrier operators, our activities in rule development and spreading best practice are more important than ever. Last year we released revised Guidelines for Liquefied Gas Carrier Structures, considering specifically the case of independent prismatic tanks. The amended text describes the technical requirements for direct strength analysis (DSA) and for fatigue assessments. DSA specifies a method for calculating yield strength and buckling strength based on net scantling of primary structural members, drawing from in-depth research and experience from other vessel types. The document also presents assessment methods taking account of the complex interaction of loads between hull structures and cargo tanks which are independent of each other. The Guidelines specify not only the design loads dominant for each structure, strength analysis methods and corrosion deductions, but the design scenarios in which assessments are required by the IMO IGC Code, therefore covering all structural requirements for gas carriers with independent prismatic tanks. The updated guidance outlines strength assessment methods against fatigue cracks caused to vessels by prolonged and repeated loads. The original guidelines assumed some very conservative starting conditions, which resulted in what we now assess to be excessively cautious fatigue life predictions. Using data on the conditions these vessels encounter in actual operation, we were able to refine our starting assumptions, which led to a more precise calculation methodology for both hull structure and independent cargo tanks and their associated support structures. Of course, field data has to be treated with caution and supported by fundamental research as it is based Hayato Suga, Director of Plan Approval and Technical Solution Division on the conditions met during normal safe operation and not behaviour in more extreme circumstances. Alternative fuels As the shipping industry pivots to cleaner modes of operation, ship owners are showing greater than ever interest in LNG as a fuel. As a case in point, Class- NK granted an Approval in Principle (AIP) to the design of an LNG-fuelled 200,000 DWT bulk carrier jointly developed by NYK Line and JMU in July 2018, to Kawasaki Heavy Industries (KHI) for their project on the concept design of an LNG-fuelled 207,000 DWT bulk carrier in January 2019, and to Sanoyas Shipbuilding Corporation for their project on the concept design of an LNG-fuelled wood chip carrier in May 2019. Despite the additional weight of their LNG fuel tanks and fuel supply systems, these ships have a larger cargo hold capacity and, by running on LNG, they are expected to satisfy Phase 3 of IMO’s Energy Efficiency Design Index (EEDI). © ClassNK 34 HANSA International Maritime Journal 12 | 2019

Schiffstechnik | Ship Technology Other than LNG, alternative fuels such as LPG and methyl/ethyl alcohol are also considered to be a viable option for ships. These alternative fuels have lower flashpoints compared to traditional fuels; therefore particular attention needs to be given to ensuring adequate safety precautions when using low-flashpoint fuels in order to decrease the potential risk of fire and explosions that may arise as a result of fuel leakage onboard the ship. International safety requirements for low-flashpoint fuels have been discussed at IMO and as a result, the International Code of Safety for Ships using Gases or other Low-flashpoint Fuels (IGF Code) has been adopted and enforced. However, the current code does not address specific regulations for alternative fuels other than LNG. To promote the design of alternative fuelled ships, we released the Guidelines for Ships Using Low-Flashpoint Fuels (Methyl/Ethyl Alcohol/LPG) which outline safety requirements for other viable alternative fuels besides LNG, based on the latest technology and regulation trends. Fuel methanation has also gathered global attention as a method of technology that may greatly contribute to the reduction of GHG emissions. ClassNK currently participates in a working group for the reduction of CO2 emissions in the international value chain by use of methane synthesized through methanation technology which combines CO2 and hydrogen produced from renewable energy sources. The technology is still relatively new, but if methanation proves to yield positive results in the long run, the supply of synthesized methane may greatly increase as it comes into widespread use. Next generation fuels As a low carbon energy source, hydrogen is stirring up excitement as a promising alternative to conventional fuels, as the only waste product discharged at the time of power generation is water. Hydrogen can be burnt directly, like HFO, or used indirectly to power fuel-cells. In marine applications, the latter option is gaining traction as the technology is proven and efficiency is improving as manufacturers develop and refine the technology. Hydrogen-powered fuel-cells could reach a theoretical efficiency as high as 80 %. It should be remembered that hydrogen is a fuel carrier and its overall environment footprint depends on how cleanly it is produced and transported to where it is needed. The benefits diminish if fossil fuels power the production process. The dynamics become more interesting, however, if renewable energy sources are employed and a lot of practical research and activity is going on in this area. Today hydrogen remains more expensive than conventional fuels, but the consensus is that costs will fall as production processes are refined and scaled up in response to growing demand, not just from shipping but more widely across industry. Therefore, in addition to economically viable and environmentally-friendly methods of production, a secure supply chain will be required to transport hydrogen to where it is needed. In common with existing fuels, ships are likely to be the most efficient method for transporting large volumes over long distances. Hydrogen transportation The technology behind the storage and transfer of bulk liquefied hydrogen is not new, with land- and barge-based facilities supporting the space industry being in place since the 1950s. The same technology and standards can be applied to carriage by sea, albeit with modifications to suit shipborne operations. Currently, the International Code for the Construction and Equipment of Ships Carrying Liquefied Gases in Bulk (IGC Code) outlines safety requirements for gas carriers like LNG. However, there are no specific requirements defined in the code applicable for liquid hydrogen carriers that take account of the hazards associated with its handling and transport. Hydrogen must be kept at temperatures below -253°C in order to maintain its liquid state under atmospheric pressure, presenting an even tougher challenge than LNG. In response to growing interest in LH2 transportation, IMO developed Interim Recommendations for Carriage of Liquefied Hydrogen in Bulk – based on proposals from Japan and Australia and subsequent follow up by a specially convened correspondence group. These proposals were adopted at MSC 97. ClassNK has taken this work further by developing Guidelines for Liquid Hydrogen Carriers based on these interim recommendations and other related international standards. These guidelines set out the safety requirements, which must be met in the design and construction of such ships to address the hazards arising from the handling of liquid hydrogen. It should be noted there are some areas where the behaviour of the cargo cannot be determined with absolute certainty. Seaborne trials will be needed to resolve this to derive the data needed to refine the requirements and develop processes necessary to support large scale commercial shipments. In 2020-2021, the world’s first project for producing and transporting clean hydrogen from Australia to Japan will begin, and ClassNK will join the project to evaluate the safety of Liquefied Hydrogen Carriers from the perspective of a classification society. HANSA International Maritime Journal 12 | 2019 35

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