ClassNK Updates Guidelines for Alternative-Fueled Ships

Revised Guidelines Cover Hydrogen and Methanol/Ethanol Vessels

Classification society ClassNK has released Edition 3.1 of its ‘Guidelines for Ships Using Alternative Fuels,’ updating safety requirements for vessels running on hydrogen and methanol/ethanol. According to a report by Maritime Executive, the revision touches Part D, which addresses hydrogen-fueled ships, and Part A, which covers methanol and ethanol.

Hydrogen Requirements Aligned with IMO Circular

The hydrogen section now incorporates the IMO’s ‘Interim Guidelines for the Safety of Ships Using Hydrogen as Fuel,’ known as MSC.1/Circ.1701, issued this year. ClassNK also added a hydrogen leak frequency table, built using a Bayesian method similar to the approach previously applied to ammonia leak estimates. This table is included as a new appendix to Part D and is intended to support the safety assessments that IMO’s guidelines require, giving designers a reference point when working with administrations for approval.

ClassNK notes it took part in the discussions that shaped the IMO hydrogen guidance, participating as a member of the Japanese delegation to the IMO Sub-Committee on Carriage of Cargoes and Containers, session 11.

New Tank Strength Rules for Methanol and Ethanol

For methanol/ethanol-fueled ships, ClassNK has introduced structural strength requirements for fuel tanks that were not specifically addressed in the corresponding IMO guidance, MSC.1/Circ.1621. The society says these standards were developed from its own experience reviewing designs of such vessels, and are meant to make tank design assessments more consistent and efficient for shipyards and designers.

Context: Broader Alternative Fuel Guidance

ClassNK’s guidelines originally compiled safety requirements across a range of fuels considered promising for cutting shipping emissions, including methanol, ethanol, LPG, ammonia and hydrogen. The rules address equipment, controls and safety devices aimed at limiting risks to crews, ships and the environment. With this update, ClassNK says it aims to keep the guidelines aligned with the latest international standards while giving industry a more complete and usable reference as newbuild activity for alternative-fueled vessels continues to grow.

The guidelines are available to registered users through ClassNK’s My Page portal on its website.