Characteristic Study of LNGC Membrane w.r.t Ni Contents of Stainless Steel

Abstract

Membrane type Cargo Containment System(CCS) for Liquid Natural Gas Carrier(LNGC) is composed of two layers of insulation and membrane. In general, membrane is made of corrugated stainless steel 304L or flat invar(FeNi36) or flat composite material. In case of stainless steel membrane, corrugation should be made to reduce the thermal stress which is induced by very low temperature of Liquid Natural Gas(LNG). Typically, corrugated membrane is produced by bending or drawing process. During the bending or drawing process, the thickness reduction of original plate is inevitable and it will degrade the mechanical characteristics of corrugated membrane. Though range of Ni content of stainless steel is from 8% to 12%, typically 8% to 10% Ni content is used since more Ni content makes cost increase of stainless steel. In order to select the proper stainless steel based on economic and safety aspects, different three studies of formability, weldability and mechanical characteristics have performed with 3 types of stainless steel. From the formability and mechanical properties studies, thickness reduction effect and strength characteristics are reviewed, respectively. Additionally, productivity was studied by weldability test. In this paper, characteristics of membrane in accordance with Ni contents of 8%, 9% and 10% of stainless steel 304L are introduced and its results are described.