Tackling ammonia leak risks in collaboration with TotalEnergies

Where ammonia stands today

As a marine fuel, ammonia holds the advantage of releasing no CO2 emissions into the atmosphere when consumed. When produced renewably – meaning that the processes behind ammonia production, such as electrolysis, use clean energy sources – it can even be a zero-emissions fuel. Because of this, ammonia has enormous potential to contribute in the long term to the net-zero shipping industry.

However, the safety risks associated with ammonia as fuel are considerable. Ammonia is toxic to humans, and exposure beyond a certain amount of time and level of intensity can have serious health consequences for crew members and other people onboard. For ship owners and designers, this represents a challenge: how to safeguard life from accidental ammonia leaks during ship operations and bunkering? Such risks must be addressed – along with challenges like developing power conversion technologies – before ammonia becomes a deployable fuel alternative.

Collaborating with TotalEnergies to de-risk ammonia

Bureau Veritas recently undertook a preliminary study alongside TotalEnergies to evaluate leak-related risks for ammonia as fuel. The energy major came to Bureau Veritas with questions about how risks from onboard ammonia leaks compared to those of liquefied natural gas (LNG). Leaning on its longstanding experience with LNG, its AMMONIA PREPARED notation* and ammonia-focused Rule Note NR 671, Bureau Veritas was able to respond.

Together, TotalEnergies and Bureau Veritas launched a study to evaluate risks from ammonia leaks, pinpoint key safety criteria and broaden the industry’s understanding of ammonia. Rule Note NR 671 was used as a guideline alongside the study, given its focus on preventing ammonia leaks and requirements for onboard vapor processing systems.

A joint preliminary study of ammonia

As specifically ammonia-powered engines and propulsion systems are still being developed, Bureau Veritas and TotalEnergies began by benchmarking ammonia’s problematic concentrations in air, comparing them to LNG. An LNG-fueled tanker served as the model for the comparison, and showed a stark contrast between the two fuels. LNG becomes dangerous at its lower flammability limit, around 50,000 parts per million (ppm), while ammonia has negative health effects at only 30 ppm when permanently exposed, or around 300 ppm when exposed for one hour. Based on this, Bureau Veritas noted that unless modifications are made to design, safety distances should be much greater for ammonia than LNG. This justified BV NR671 approach with more stringent leak management on-board and vapor gas processing to avoid even small leaks reaching manned areas.

With this in mind, Bureau Veritas and TotalEnergies explored multiple ways to model leaks, and assess their effects on passengers and crew members. Experts evaluated different scenarios regarding the frequency and volume of leaks for single wall and double wall containment, as well as during bunkering operations. The study accounted for the thermodynamic properties of leaked ammonia and used high-end engineering tools to determine leaks’ changing flows and concentrations. Key areas studied included:

  • Preliminary estimates of the ammonia concentration in case of leaks (e.g., the double wall pipes annular space and fuel preparation room)
  • Guidance to determine the size of associated safety systems (e.g., ventilation, vapor processing systems)
  • Effects of leaks in the engine room, in the case of ammonia passing through the storage tank’s primary and secondary barriers
  • Size of safety zones around vent masts for ships not equipped with a vapor processing system
  • Health risks to persons in the area exposed to ammonia leaks

Study opens new avenues for ammonia

While further experimentation and analysis are required to reach definitive conclusions, this preliminary study helped identify future areas to explore for de-risking ammonia as fuel. Additional tests could be performed for leak design scenarios, bunkering safety zones, bunkering arrangements, the effect of weather conditions, and more.

Ideally, technology will eventually evolve enough to eliminate ammonia leaks completely. Until then, leak mitigation and treatment remain the best course of action for ship owners and designers. Bureau Veritas’ preliminary study with TotalEnergies forms a strong basis for future industry collaboration, providing a foundation for ammonia as fuel advancement. By pairing the right questions with the right tests, marine stakeholders can begin the journey to de-risking ammonia as fuel, as they did for LNG.

Bureau Veritas’ contributions to ammonia

In addition to this preliminary study and NR 671, Bureau Veritas is actively participating in multiple industry-wide ammonia projects. In partnership with Jiangnan Shipyard Group, Bureau Veritas is helping develop the world’s largest ammonia-powered VLAC, standing at 93,000 m3. Meanwhile, Bureau Veritas is classing future ammonia-fueled vessels with our AMMONIA-PREPARED notation, including two liquefied petroleum gas (LPG) carriers for shipowner Geogas.

With these and other projects, Bureau Veritas is doing its part as a classification society to de-risk an alternative fuel with enormous potential. We work by our clients’ side, using our technical expertise to improve the safety of ammonia as fuel, and accelerate decarbonization for the entire marine industry.


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