ClassNK tightens leakage and fuel tank guidelines for alternative-fuelled ships

Japanese classification society ClassNK has updated its safety requirements for vessels running on alternative fuels, introducing hydrogen leak prevention measures alongside new structural strength mandates for methanol and ethanol fuel tanks.

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The revised standards for hydrogen-fuelled vessels integrate the International Maritime Organization's (IMO) interim guidelines, while introducing a hydrogen leak frequency table, for risk evaluations required under the IMO guidelines.

The bilge system – a network of pipes, pumps, and valves designed to collect accumulated water from the lowest part of a ship's hull – should have high-level alarms, ClassNK said.

“Low-temperature alarms should be fitted, if liquid hydrogen leakage is possible,” the classification society added in its report.

The classification society has introduced new structural strength mandates for fuel tanks for vessels operating on methanol and ethanol.

For example, air inlets to hazardous enclosed spaces should be close to the floor and the air extraction should be placed close to the ceiling of said space, keeping in mind the space geometry, ClassNK said.

“Additional extraction outlets will be required to be placed in areas where there is a risk of formation of gas pockets from ceiling configurations” including structural beams, cable trays and pipe racks, the classification society said.

With this revision in protocols, shipyards, vessel designers and owners will be able to further assess safety of alternative-fuelled ships, staying in line with global standards, ClassNK added.

By Aparupa Mazumder

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