ClassNK published estimated leak frequencies of ammonia fuel from onboard components for ammonia-fueled ships, usable for risk assessment. The estimated leak frequencies were added as an appendix of “Part C of Guidelines for Ships Using Alternative Fuels (Edition 3.0)”.

Ammonia, which does not emit CO2 when burned, is expected to be utilized as an alternative fuel for ships, and various studies and developments are currently underway toward the practical application of ammonia-fueled 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.

Therefore, 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, they used Bayesian method to estimate the probability of ammonia leak from each component combining with 1) the onshore ammonia leak frequency data in Japan extracted from the database of the High Pressure Gas Safety Institute of Japan, and 2) the LNG leak frequency data in LNG-fueled ships. Thus probability estimation using Bayesian method apply for the risk assessment of substances with few actual operation, such as hydrogen. This is the first time in the world to estimate the ammonia leak frequency in onboard component for ammonia-fueled ships.

By using this estimated leak frequency in onboard components for ammonia-fueled ships, a more reasonable and reliable risk assessment is achieved.

As part of the “ClassNK Transition Support Services” that comprehensively supports our 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 via “Guidelines” of My Page on ClassNK’s website after registration.
https://www.classnk.or.jp/account/en/Rules_Guidance/ssl/guidelines.aspx

Table: Estimated Leak frequencies for onboard ammonia fuel components