ClassNK revises safety rules for hydrogen, methanol ship

It added hydrogen leak-frequency data to its safety requirements.

ClassNK has revised its safety guidelines for alternative-fuelled ships, adding hydrogen leak-frequency estimates and new structural requirements for methanol and ethanol fuel tanks.

The revision incorporates the International Maritime Organization’s (IMO) Interim Guidelines for the Safety of Ships Using Hydrogen as Fuel (MSC.1/Circ.1701), issued this year.

ClassNK also added a hydrogen leak-frequency table for safety assessments required under the IMO guidelines.

It used a Bayesian method to estimate hydrogen leak frequencies for ships. The method combines new observations with existing information to estimate a target probability.

The estimates are intended to support ship design and safety assessments for alternative-fuelled ships.

The revised guidelines also introduce structural strength requirements for methanol and ethanol fuel tanks. ClassNK said the requirements address areas not covered by the relevant IMO guidelines, MSC.1/Circ.1621.

The changes form part of the third edition of ClassNK’s Guidelines for Ships Using Alternative Fuels, which covers methanol, ethanol, liquefied petroleum gas, ammonia, and hydrogen.

ClassNK said it developed the methanol and ethanol tank requirements based on its experience reviewing the design of such ships. The requirements provide a basis for tank design assessments.

ClassNK participated in the 11th session of the IMO Sub-Committee on Carriage of Cargoes and Containers as part of the Japanese delegation during the development of the hydrogen guidelines.

“Through this revision, shipyards, designers, and shipowners can carry out design and safety assessments in line with the latest international standards,” ClassNK said.

The guidelines set requirements for equipment, controls, and safety devices to address risks associated with alternative fuels to ships, seafarers, and the environment.