Experimental Study on the Cryogenic Storage Tank made of High Manganese Steel

摘要

In this study, we experimentally demonstrate the feasibility of using high manganese steel as a cryogenic applications such as LNG–FPSO (Liquefied Natural Gas – Floating Production Storage Offloading), LNG fuel tank, and LNG carrier. High manganese steels, steels with high manganese concentrations at 22.0 ~ 26.0 wt.%, are recently getting the spotlight in the cryogenic market since it provides excellent physical properties at very low temperatures similar to those of widely used cryogenic materials such as aluminum alloy, 9% Ni steel, and 304 stainless steel with relatively low cost. Intensive studies have been performed on the specimen to investigate on the physical properties of high manganese steel at cryogenic temperatures. However, the stability of the final product such as LNG storage tank has not been studied when it is made of high manganese steel. The objective of this study is to evaluate the integrity of cryogenic storage tank made of high manganese steel when it is exposed to repeated thermal cycle from room temperature to cryogenic temperatures below -150 °C. A bellshaped cryogenic storage tank is made of 15 mm thick high manganese steel which is developed and produced by POSCO, Korea. Liquefied nitrogen (LN2) is kept to be supplied to cool down the tank and begins to be drained when the temperature of the tank reaches below target temperature (under -163 °C). Inside of the tank is maintained at ambient pressure to prevent the failure of tank due to high pressure. Welded regions are inspected by nondestructive radiographic testing (RT) before and after the experiments in order to check the integrity of tested tank. It is concluded that the cryogenic storage tank made of high manganese steel was kept stable and safe after experiencing repeated thermal cycles.