ClassNK okays ammonia fuel tank design for GSC’s containerships

Classification society ClassNK has awarded an approval in principle (AiP) for the design of a prismatic ammonia fuel tank (IMO Type B independent tank) for containerships developed by Planning and Design Center for Greener Ships (GSC).

The Type B tank developed by GSC has been designed to ensure safe storage of ammonia and to minimize the reduction in the number of cargo containers due to the placement of fuel tanks in consideration of operational needs.

Furthermore, the shape of the storage space for the tank has been simplified from the typical bench corners for container carriers, improving constructability and increasing the fuel volume, according to ClassNK.
 
The classification society carried out the design review of the tank based on Part GF of its “Rules and Guidance for the Survey and Construction of Steel Ships” incorporating the Code and “Guidelines for Ships Using Alternative Fuels (Edition 2.1)”.

Upon confirming that it complies with the prescribed requirements, ClassNK awarded the AiP.

Ammonia is expected to be used as a marine fuel for shipping decarbonization since it does not emit CO2 when combusted. However, its utilization presents challenges, such as the risk of leakage and relatively low volumetric efficiency.

While Type B tanks require a refined fatigue analysis, it is possible to use ordinary steel as the material for the structure of fuel storage holds space, except for the bottom part which is intended to be a partial secondary barrier, resulting in a reduction in the amount of steel for low-temperature service. Additionally, prismatic tanks offer superior volume efficiency compared to cylindrical tanks as they can be designed to fit the ship’s hold.

According to the UK-based research and consultancy firm Maritime Strategies International (MSI), the next 25 years are likely to see ammonia trade transformed with clean ammonia providing new demand for close to 400 very large gas carriers, compared to a current fleet of 375 focused on carrying liquefied petroleum gas (LPG).

In contrast, though a requirement for around 215 methanol carriers will be significant, it compares to an aggregate methanol-capable 35,000dwt and above fleet of 280 at the end of 2023.