ClassNK has published estimated leak frequencies of ammonia fuel from onboard components for ammonia-fuelled ships, usable for risk assessment, and which have been added as an appendix to Part C of ‘Guidelines for Ships Using Alternative Fuels (Edition 3.0)’.
Ammonia, which does not emit CO2 when burned, is expected to be used as an alternative fuel for ships, and various studies and developments are currently underway toward the practical application of ammonia-fuelled ships. Such ship design incorporates risk assessment, and risk assessment involves the consideration of the probability of ammonia leak from each component. However, statistical data of onboard ammonia leak have been extremely limited, therefore probability estimation of onboard ammonia leak was difficult.
ClassNK, in collaboration with the Research Institute of Science for Safety and Sustainability (RISS), a department of the National Institute of Advanced Industrial Science and Technology (AIST), conducted probability estimation of the ammonia leak. Specifically, the Bayesian method was used to estimate the probability of ammonia leak from each component combining with:
- the onshore ammonia leak frequency data in Japan extracted from the database of the High Pressure Gas Safety Institute of Japan, and
- the LNG leak frequency data in LNG-fuelled ships.
This probability estimation using Bayesian method can be applied to the risk assessment of substances with little actual operation experience, such as hydrogen. This is the first time it has been used to estimate the ammonia leak frequency in the onboard component for ammonia-fuelled ships. By using this estimated leak frequency in onboard components for ammonia-fuelled ships, a more reasonable and reliable risk assessment is achieved.
As part of the ‘ClassNK Transition Support Services’ that comprehensively supports customers’ smooth transition to zero-emission, ClassNK will continue to promote initiatives for the safe use of ammonia and other alternative fuels. The guidelines are available to download for registered users of the ClassNK website.
Image: ‘Guidelines for Ships Using Alternative Fuels (Edition 3.0)’ (source: ClassNK)
