ClassNK has revised the safety requirements for ships using methanol/ethanol and hydrogen as fuel within the ‘Guidelines for Ships Using Alternative Fuels (Edition 3.1).’
In Part D, covering hydrogen-fueled ships, the revision incorporates the ‘Interim Guidelines for the Safety of Ships Using Hydrogen as Fuel (MSC.1/Circ.1701)’ issued by the IMO this year, and additionally introduces a hydrogen leak frequency table that can be used for the safety assessments required under the IMO guidelines. In Part A, covering methanol/ethanol-fueled ships, new structural strength requirements for methanol/ethanol fuel tanks—which are not addressed in the IMO guidelines have been established.
Through this revision, shipyards, designers, and shipowners can carry out design and safety assessments in line with the latest international standards, and by utilizing ClassNK's own leak frequency estimates and the relevant requirements, they can proceed the development of alternative-fueled ships in a more rationally.
Background
As the building of alternative-fueled ships advances in response to the global challenge of reducing GHG emissions, ClassNK has comprehensively compiled the safety requirements for ships using methanol, ethanol, LPG, ammonia, and hydrogen—fuels regarded as promising alternatives—and has issued the guidelines. Taking into account the risks that the use of alternative fuels poses to the environment, seafarers, and ships, the guidelines set out requirements for equipment, controls, and safety devices to minimize such risks.
With the issuance of the IMO guidelines for hydrogen-fueled ships (MSC.1/Circ.1701), ClassNK has fully incorporated the IMO guidelines to make the guidelines more user-friendly for shipyards, designers, and shipowners, while also enhancing the requirements serving as design and assessment guidance for other alternative fuels. In the development of the IMO guidelines, now reflected in Part D, ClassNK participated as a member of the Japanese delegation to the IMO Sub-Committee CCC 11*¹ and contributed to the discussions.
Examples of Revisions
Hydrogen-fueled ships (Part D): The relevant IMO guidelines (MSC.1/Circ.1701) have been incorporated, and a full-scale revision has been carried out. In addition, as with the estimation of ammonia leak frequency*², a Bayesian method*³ was applied to derive estimated hydrogen leak frequencies for ships, which have been added as Appendix 2 to Part D. These enable ship designs and their safety assessments—required for administration approval of alternative-fueled ships—to be conducted in a more rational and reliable manner.
Methanol/ethanol-fueled ships (Part A): Based on ClassNK's experience in the design review of such ships, structural strength requirements for methanol/ethanol fuel tanks—which were not specifically stipulated in the relevant IMO guidelines (MSC.1/Circ.1621)*⁴—have been developed and standardized. This enables the efficient implementation of tank design assessments.
As a third-party certification body, ClassNK will continue to support your efforts to address environmental challenges through the development of standards, certification, and the provision of information.
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