CRYOGENIC RELIABILITY OF THE SANDWICH INSULATION BOARD FOR LNG SHIP

Abstract

Liquefied natural gas (LNG) is mainly carried by the LNG ship, whose cargo containment system is composed of dual barriers of LNG and insulation board. The insulation board of LNG containment system should have cryogenic reliability and high thermal insulation performance for safe and efficient transportation of LNG. The polyurethane foam reinforced with glass fiber of 0.5 % volume fraction (called RPUF), has been used for the insulation board. Although the thermal stress in neat polyurethane foam (PUF) was less than the failure strength of PUF, the RPUF was used for insulation board due to the low fracture toughness of PUF. However, the RPUF not only increased the manufacturing cost of LNG ship, but also decreased the thermal insulation characteristics of PUF, which is a remaining concern in LNG ship building industries. In this study, the surface area of PUF for insulation board was reinforced selectively at the area under high thermal stress with glass fiber polymer composite, which was a sandwich construction to decrease the production cost and to increase the thermal insulation characteristics. Finite element analysis was conducted to estimate the thermal behavior of insulation board at the cryogenic temperature and a new experimental method was developed to investigate reliability of insulation board using fracture mechanics. From the experimental results, it was found that the reliability of insulation board composed of PUF increased considerably by reinforcing selectively the PUF with the glass fiber composite at the cryogenic temperature.