ClassNK adds membrane requirements for hydrogen carriers

Update covers vacuum insulation and emergency response for new vessel designs.

ClassNK has revised its liquefied hydrogen carrier guidelines, adding requirements for membrane-type cargo containment systems and updating material and welding guidance.

The update incorporates the “Revised Interim Recommendations for Carriage of Liquefied Hydrogen in Bulk” adopted by the International Maritime Organisation in 2026.

Following the adoption of the recommendations at MSC 111, the revised guidelines introduce requirements for liquefied hydrogen carriers fitted with membrane tanks using vacuum insulation.

They clarify design requirements for vacuum insulation systems, monitoring devices, pressure control equipment and emergency response.

The requirements are intended to support design studies and safety assessments for new liquefied hydrogen carriers with membrane-type cargo containment systems, including work towards Flag Administration approval and safety demonstration.

ClassNK has also updated verification procedures for metallic material selection, testing, and quality control.

The revised guidance addresses material degradation risks that require attention in liquefied hydrogen carrier design, including low-temperature embrittlement, hydrogen embrittlement, and hydrogen attack.

ClassNK said the changes are expected to reduce the risk of design changes and additional verification