To minimise operational disruption, large containerships need to refuel while loading and discharging cargo. To this end, French carrier CMA CGM’s ultra large dual-fuel containerships were designed to accommodate 18,600 cbm of LNG and bunkering is likely to take up to 15 hours.

Bunkering a vessel is a process involving connecting lines, pressure testing, transferring LNG, purging the lines and bunker station, inserting the lines again, and ultimately disconnecting them. It also involves the delivery of a bunker delivery note, which is required by the International Code of Safety for Ships using Gases or other Low-flashpoint Fuels ( IGF Code).

While 15 hours may seem like an eternity, the 40 hours required for the cargo operations of a large containership calling at a major port should leave ample time for large-scale gas bunkering operations.

A more critical challenge that must be addressed is to help ensure the safe, efficient ship-to-ship transfer of LNG is the identification and allowance of a reasonable safety zone—while minimising the impact on cargo operations as much as possible.

Martial is the Regional General Manager Sustainable Shipping at Bureau Veritas Marine & Offshore.

Bureau Veritas conducts risk assessments that determine how large a safety zone needs to be. If deemed necessary, this analysis is supplemented by gas cloud dispersion model analysis (using a deterministic approach) ISO 20519, and The Society for Gas a Marine Fuel (SGMF) Safety Guidelines for LNG bunkering.

Simultaneous cargo and bunkering operations do not necessarily pose an increased level of risk. And a safety zone is not necessarily the same as an exclusion zone. But within a gas bunkering safety zone, it is necessary to control, monitor, detect, protect against, and mitigate any consequences of potential LNG leakage, as modeled in certain scenarios. This analysis incorporates operational experience, the appropriate crew training, terminal operator information, safety procedures, and the reliability of cryogenic transfer equipment allowing for the possibility of using entire vacuum-insulated double-wall transfer lines that have been developed for LNG bunkering operations on passenger ships.

In summary, with proper care, appropriate precautions, trained personnel, and established procedures, regular LNG bunkering is not significantly more complicated than conventional heavy fuel oil (HFO) bunkering. Furthermore, conventional pollution prevention is not a risk so oil spill prevention measures are not required.

LNG fuel quality

The quality of conventional HFO bunker fuels has long been a challenge for the shipping industry. There have been a variety of quality issues to be managed and tested to ensure that required and contractual standards are met. LNG quality also needs to be assured.

One key factor in establishing the quality of LNG fuel is the methane number (MN). But it is not the only factor. Temperature is also important, as are other parameters where dual-fuel boilers are used. Custody transfer from the LNG bunker vessel to the receiving ship is also part of this, as the energy transferred must be quantified and a deduction made for the vapor return.

The use of Coriolis flowmeters and spectrographs on board LNG bunker vessels eases transfer of commercial data and will help eliminate potential disputes. An ISO standard— CD 23306 LNG fuel specification for marine applications—is currently being developed to select a comprehensive method for MN calculation. Bureau Veritas is actively involved in this work, so feel free to reach out if you want to learn more.

Gas expertise

A broad group of stakeholders is involved in LNG bunkering safety: ISO, EMSA, IACS, IAPH, CSA, USCG, SGMF and SEA/LNG. All are working—together where appropriate—to secure a strict application of safety guidelines and international standards and, where possible, ensure the harmonisation of rules and standards. Bureau Veritas is playing a pivotal role in the evolution of LNG power, sharing its experience and supporting the industry in developing safe LNG bunkering arrangements, technology, standards and operations.

ABOUT THE AUTHOR

Martial is the Regional General Manager Sustainable Shipping at Bureau Veritas Marine & Offshore (BV), with the primary role of supporting the development of LNG as fuel and alternative energy in North Asia. He has been involved in crafting new safety rules and guidelines for the use of LNG as a bunker fuel within BV and has also worked with other bodies such as SGMF, IACS and EMSA as a high-level expert. Martial played a key role on assessing CMA CGM's 23,000-teu dual-fuel containerships, including the safety of LNG bunkering and notably SIMOPS operations. He has been also led in advising on other LNG projects including the propulsion of very large cruiseships. Previously, he managed the FP7 project Ulysses on innovative energy efficiency systems and has a Masters Engineer Degree in Naval Shipbuilding. He joined Bureau Veritas in 2006 as a propulsion and safety design engineer. His previous roles were at Chantiers de l’Atlantique and DCNS in France and Singapore, respectively. He started his career in the French Navy as a mechanical engineer.