ClassNK Releases ‘Guidelines for Liquefied Hydrogen Carriers (Edition 3.1)’

ClassNK has released updated guidelines for liquefied hydrogen carriers, edition 3.1. These guidelines integrate the "Revised Interim Recommendations for Carriage of Liquefied Hydrogen in Bulk" adopted by the IMO in 2026, updating safety requirements and offering guidance on materials and welding practices for hydrogen equipment. This revision aims to facilitate design studies and safety assessments for shipyards, designers, shipowners and other maritime stakeholders.

Liquefied hydrogen carriers are gaining worldwide attention as a means of large-scale transportation of hydrogen, a key energy carrier for a decarbonized society. Recent developments have led to diverse designs, including some fitted with membrane-type cargo containment systems. The 2026 recommendations introduced additional safety requirements for these systems, prompting the update of ClassNK Guidelines to reflect these changes.

The revised guidelines now include specific requirements for membrane-type cargo containment systems, drawing on the IMO interim recommendations. This covers vacuum insulation systems, monitoring devices, pressure control equipment and emergency response. The updated guidance on materials and welding for hydrogen equipment is based on ClassNK's practical experience, clarifying verification procedures for metallic materials, testing and quality control.

This aims to reduce risks from material degradation issues such as low temperature embrittlement, hydrogen embrittlement and hydrogen attack.

As a third-party certification body, ClassNK continues supporting stakeholders in their efforts to tackle environmental challenges through standards development, certification and provision of technical information.