The interim guidelines for applying high manganese austenitic steel to LNG storage and fuel tanks have been approved by the 100th Maritime Safety Committee(MSC) at the International Maritime Organization(IMO).
High manganese austenitic steel was developed by POSCO, South Korea’s largest steel maker for use in LNG storage and fuel tanks in 2013. However, before the MSC’s approval, only four types of material which included 9% nickel steel, aluminum alloy, stainless steel and Invar were authorized for use in the building of LNG tanks by the IMO.
The high manganese austenitic steel has many advantages, offering reduced costs, low price volatility, and higher tensile strength compared to the other four alternatives - 9% nickel steel, aluminum alloy, stainless steel and Invar.
Over the last year, Korean Register(KR) - an IACS member classification society - has worked to develop the interim guidelines in close cooperation with the Ministry of Oceans and Fisheries(MOF) of Republic of Korea and POSCO. The draft was agreed at the 5th Sub-Committee on the Carriage of Cargoes and Containers in September 2018, with final approval secured at the 100th MSC.
The first vessel to use high manganese austenitic steel for its LNG fuel tank was constructed at Hyundai Mipo Dockyard in July 2016. It is a 50,000 dwt LNG-fueled bulker constructed in accordance with Harmonized CSR and classed by KR. KR conducted an intensive analysis to assess the safety of the base metal and welds, to ensure the safety of this vessel and to develop the exact specification for the high manganese austenitic steel. The completed vessel has been chartered by POSCO to transport limestone cargoes in the Korean coastal trade.
Changwook Kim, the head of KR’s technical division and executive vice president of KR said: “With the MSC’s approval, the industry now has more options to choose from when building LNG tanks and storages, with high manganese austenitic steel offering a cost effective and environmentally-friendly alternative. Furthermore, KR as a classification society, is now working to develop high manganese austenitic steel that complies with the IGC Code (International Code for the Construction and Equipment of Ships carrying Liquefied Gases in Bulk) and the IGF Code (International Code of Safety for Ships Using Gases or Other Low-Flashpoint Fuels) in near future.”