Chemical tanker features novel stainless steel cargo tanks

18 Nov 2014
‘Sunrise Hope’ – first Japanese chemical carrier to use duplex stainless steel and clad steel in its tanks

‘Sunrise Hope’ – first Japanese chemical carrier to use duplex stainless steel and clad steel in its tanks

Japanese class society ClassNK reports that the first chemical tanker to use a combination of duplex stainless steel and stainless clad steel in the construction of its cargo tanks has now been delivered.

The 12,500dwt tanker was built for Hiro Naviera at the Usuki Shipyard. The application of duplex steels in the vessel’s cargo tanks was made possible thanks to a joint research program between steel manufacturers, technical universities, and ship designer, and which was supported by ClassNK as part of its ‘Joint R&D for Industry’ programme.

The tanker, named Sunrise Hope, is of an eco-ship design, equipped with 14 cargo tanks, all which employ duplex stainless steel technology. Construction of the vessel was carried out in accordance with ClassNK’s Guidelines on Welding of Duplex Stainless Steels, which were released in January 2014, this being the first time the guidelines have been used in the construction of an actual vessel.

According to ClassNK, duplex stainless steel provides significantly greater strength and excellent corrosive resistance in comparison with the commonly used austenitic stainless steel SUS316LN, while its low nickel composition makes it economical. Although duplex stainless steel technology has been used previously in shipbuilding internationally, this marks the first time that a combination of both duplex and stainless clad steels have been used in the construction of a chemical tanker’s cargo tanks. It is also the first time that duplex stainless steels have been used in a Japanese shipyard, while the lean duplex stainless steel which contains lower nickel compared to duplex stainless steel has been used in some cases.

Duplex stainless steels consist of a mixture of both austenite and ferrite phases and are said to offer enhanced strength and corrosion resistance superior to that of commonly used austenitic stainless steels. On the Sunrise Hope, duplex stainless steel KSUS329J3L replaces the commonly used SUS316LN for the bulkheads inside the cargo tanks, while the bulkheads adjacent to the cargo tanks were constructed using stainless clad steel, in which stainless steel and carbon manganese steels have been compression bonded together into a single plate. The stainless clad steel of the ballast tanks ensures the coating quality of the tanks is protected.

The team involved in the project comprised JFE Steel Corporation, Nippon Steel & Sumikin Stainless Steel Corporation (NSSC), Taseto, and ClassNK, with the support of the Nagasaki Institute of Applied Science and Consultancy Juk Fnadyke. ClassNK says that the team’s wealth of specialist knowledge and extensive expertise spanning from material development to ship construction ensured the technology was successfully applied to this first vessel.

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