ClassNK publishes ammonia leak estimates    

Believed to be an industry first, the estimated leak frequencies were added as an appendix of Part C of Guidelines for Ships Using Alternative Fuels (Edition 3.0).

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

However, ammonia does leak and is extremely toxic, posing serious threats to human health even in small shipboard leaks. Shipowners will be challenged to safeguard life through enhanced ship design, improved vapour gas processing and greater safety zones than is the case for LNG.

While ammonia has been carried by ships for decades, it has never been used as a marine fuel. Risk assessments for ammonia-fuelled ship designs involve considering the probability of an ammonia leak from each component, but statistical data of onboard ammonia leaks have been extremely limited, making probability estimation 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 a probability estimation of the ammonia leak.

The data was compiled used the Bayesian method 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. 

Thus probability estimation using Bayesian method apply for the risk assessment of substances with few actual operations, such as hydrogen. ClassNK said it hopes the use of an estimated leak frequency in onboard components for ammonia-fuelled ships can lead to a more reasonable and reliable risk assessment.

The guidelines are available to download on the class society’s website after registration.