Japanese classification society ClassNK has revised its liquefied hydrogen carrier rules to cover membrane-type cargo containment systems using vacuum insulation, according to a company statement.
Edition 3.1 of the "Guidelines for Liquefied Hydrogen Carriers", released on 10 September 2026, incorporates the IMO's "Revised Interim Recommendations for Carriage of Liquefied Hydrogen in Bulk", adopted in 2026 at the 111th session of the Maritime Safety Committee, or MSC 111.
The revision sets requirements for membrane tanks using vacuum insulation and clarifies design provisions for vacuum insulation systems, monitoring devices, pressure control equipment and emergency response.
The rules are intended to give developers of new liquefied hydrogen carrier designs a recognised safety framework for work towards Flag Administration approval and safety demonstration.
ClassNK has also updated verification procedures covering metallic material selection, testing and quality control for hydrogen equipment.
The revised guidance addresses low-temperature embrittlement, hydrogen embrittlement and hydrogen attack, areas that can require particular attention in liquefied hydrogen carrier design and may otherwise lead to design changes or additional verification.
The guidelines also reflect experience gained from the construction and operation of demonstration vessels and from research and development projects as liquefied hydrogen carrier designs become more diverse.
ClassNK is a Japanese third-party classification and certification organisation that develops technical standards, carries out certification and provides technical information to the maritime industry.