The Korean Register (KR) has awarded Approval In Principle (AIP) for an LNG carrier with a prismatic IMO type-B tank built by Hyundai Mipo Dockyard (HMD). The ship is a small to medium-sized LNG carrier with a B-type cargo tank developed as a result of a technical collaboration project between KR and HMD, which began in February 2020.

The type-B tank is usually applied to the fuel tanks of large sized container ships or bulk carriers but HMD has developed the technology to apply it to small and medium-sized LNG carriers of 30,000 m³ capacity. KR has carried out the cargo hold fatigue analysis, the crack propagation analysis and gas leakage rate calculation and has verified the new LNG carrier’s compliance with the IGC Code (the International Code for the Construction and Equipment of Ships carrying Liquefied Gases in Bulk).

While membrane-type hull and cargo holds have been designed and built for large ships, there is a growing interest in applying the same technology to small and medium-sized LNG carriers in order to meet increasing demand for LNG as an eco-friendly fuel and the expansion of LNG bunkering infrastructure.

The advantage of the HMD type-B tank lies in the possibility of a separated design for the hull and the cargo tank, ensuring appropriate structural stability inside the tank to manage the impact load caused by the motion of the liquid cargo, and through its design flexibility as a fuel tank.

The LNG cargo tank has been developed through high-level engineering, for example, crack propagation analysis has been used to install a partial drip tray which is installed in the lower part of the LNG cargo tank by calculating the amount of leaked gas in the support structure which is supporting the cargo tank.

Nam Young-joon, executive vice president of HMD, said, “The partial second barriers have made it difficult to design this type B cargo tank, but the potential high hull space utilization has driven the development of this technology. We expect increasing demand for small and medium-sized LNG carriers in the future, as a direct result of this AIP.”

Kim Yeon-tae, executive vice president of KR Technical Division said, “Through this joint cooperation, KR has successfully developed the technology and plan approval to apply B-type cargo tanks to small and medium-sized LNG carriers, we will continue to provide the technical support needed by Korean shipbuilding industry to support the development of new market-leading concept ships.”