exploring new insights towards rationalizing design of liquefied hydrogen carriers and hydrogen-fueled ships –

ClassNK has commenced joint research with the Japan Aerospace Exploration Agency to establish an evaluation method for the compatibility of ship materials with liquefied oxygen . The aim is to contribute to suppressing fire accidents on ships handling liquefied hydrogen, where LOX could be generated, and to reasonable material selection.

To construct a supply chain for hydrogen, which is expected to be a clean energy source in a decarbonized society, the development of liquefied hydrogen carriers that enable large-scale and efficient transportation is progressing actively. Liquefied hydrogen is also attracting attention as a potential next-generation fuel for ships.

The surrounding air may be cooled to below its boiling point, potentially resulting in the generation of LOX under some situations of liquid hydrogen storage. Due to the high concentration of oxygen like LOX, which has a strong oxidizing property, there is concern that materials exposed to LOX could ignite upon impact. The International Maritime Organization (IMO) has pointed out this safety risk of materials used in liquefied hydrogen carriers in its “Interim Recommendations for Carriage of Liquefied Hydrogen in Bulk”*1. In ClassNK’s “Guidelines for Liquefied Hydrogen Carriers”, consideration for LOX in materials used for liquefied hydrogen tanks, pipes, pressure vessels, and equipment where an interface with the atmosphere becomes extremely low temperatures due to liquefied hydrogen, is stipulated as a requirement.

To contribute to the rational design of ships handling liquefied hydrogen, which is expected to increase, ClassNK has gathered knowledge from the aerospace field, where LOX has been used as rocket fuel for a long time. For further investigation, ClassNK embarks on joint research with JAXA, which possesses extensive knowledge and experience related to the safety usage of LOX. The research aims to establish an evaluation method for LOX compatibility, the material’s property to resist ignition even when exposed to LOX environments, suited for the maritime field. The parties will engage in identifying challenges related to LOX compatibility in onboard environments, organizing countermeasures, and conducting verification through testing.