ClassNK Updates Alternative Fuel Guidelines to Align Hydrogen and Methanol Standards with IMO Regulations
The Japanese ship classification society, ClassNK, has issued a new update to its guidelines for alternative fuel ships, aligning its hydrogen requirements with the new International Maritime Organization (IMO) standards. The update also introduces structural requirements for methanol and ethanol fuel tanks that are currently not covered by international guidelines.
Version 3.1 of the "Guidelines for Ships Using Alternative Fuels" updates the sections covering hydrogen, methanol, and ethanol fuels. The broader regulatory document also encompasses liquefied petroleum gas (LPG) and ammonia.
For ships operating on hydrogen fuel, ClassNK has incorporated the new interim guidelines issued by the IMO regarding the safety of ships using hydrogen as fuel, which were approved by the Maritime Safety Committee last May. The IMO guidelines address the design, arrangement, and systems necessary to manage hydrogen-specific fire, explosion, and leakage risks.
Taking an additional step, ClassNK has incorporated estimates for hydrogen leakage rates from onboard equipment. Calculated using an established methodology previously applied by the society to ammonia systems, these figures aim to provide designers with the critical risk assessment data required when applying for approval from the ship's flag administration concerning emissions reductions.
Meanwhile, the section on methanol and ethanol has been expanded to include structural strength requirements for fuel tanks. ClassNK noted that these specifications are based on its extensive experience in reviewing ship designs, thereby covering an area currently unaddressed by existing IMO guidelines for vessels utilizing methanol or ethanol as fuel.
The classification society first introduced specific requirements for hydrogen-fueled ships to its guidelines in Version 3.0 in 2024, prior to the completion of the IMO framework. Those initial requirements addressed issues such as hydrogen ignition, explosion prevention, and leakage risks.
ClassNK has been progressively evolving this regulatory document as alternative fuel projects move closer to commercial viability. A previous version released in 2022 introduced detailed requirements for ammonia-fueled ships, while the IMO subsequently published estimates for ammonia leakage rates to be utilized in onboard risk assessments.
This latest amendment arrives as the IMO continues to bridge gaps within the safety framework for emerging marine fuels. Following the approval of the hydrogen guidelines at the 111th session of the Maritime Safety Committee, ongoing efforts are underway to establish mandatory provisions for methanol and ethanol, alongside broader regulations for other alternative fuels and technologies.
