New bulker uses impact-absorbing steel

14 Aug 2014
MOL’s latest bulk carrier - of a similar type to this ship - makes use of a new ductile steel material developed in Japan

MOL’s latest bulk carrier - of a similar type to this ship - makes use of a new ductile steel material developed in Japan

Mitsui OSK Lines (MOL) says that a newly-launched bulk carrier which it operates is the first ship to use a new type of highly ductile steel plate.

The steel material, known as NSafe-Hull, has been developed in Japan by Nippon Steel and Sumitomo Metal Corporation. The steel is designed to absorb side impact to the hull three times more effectively than conventional steel plate, which is claimed to reduce the risk of cracks in the hull and significantly increase vessel safety.

The new bulk carrier was built by Imabari Shipbuilding, and launched on 2 August. The 299.4m long, 206,600dwt ship used a total of about 3,000t of NSafe-Hull, which was used for sections such as the side plates of cargo holds and fuel tanks. According to MOL, these are areas where hull strength is especially critical, improved puncture resistance helping to prevent flooding, protect the cargo, and reduce risk of environmental damage from oil leakage.

NSSMC describes NSafe-Hull as “a highly ductile steel plate for shipbuilding with improved collision safety”. It was jointly developed by NSSMC, Imabari Shipbuilding and Japan’s National Maritime Research Institute (NMRI). The material is claimed to offer excellent ductility, while maintaining the workability (e.g., machinability and weldability) of conventional steels, which substantially improves ship’s collision safety. NSSMC says it developed NSafe-Hull through “designing chemical composition and micro-structural control in crystalline scale.”

The benefits of the material are further detailed by NSSMC, which says that if a ship is made of NSafe-Hull, because of the superior ductility of the material, the energy absorbed in a side-on collision before the hull actually breaks could be roughly three times greater than for a ship made of conventional steels.

NSSMC plans to conduct more advanced analyses, under a ClassNK scheme known as ‘Joint R&D with Industries and Academic Partners’. As part of this exercise, ClassNK is considering assigning special high-safety notations to vessels designed to higher than normal safety standards, such as those in the construction of which the NSafe-Hull material is employed.

Meanwhile, NSSMC, Imabari Shipbuilding and NMRI say that they “will continue contributing to safe, secured and environmentally friendly marine transportation by promoting the adoption of NSafe-Hull for a wide variety of ships.”

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