Design of an IMO Type B prismatic vessel for liquefied natural gas storage

Abstract

This study proposed a design methodology for an IMO Type-B prismatic storage vessel for liquefied nat-ural gas. The design of this vessel refers to the IGC Code that provides the international standards for storage of liquefied gases in bulk. The internal pressure was resulted from the vapor pressure and the internal liquid pressure. The liquid pressure was calculated from the effect of gravity and the accelerations applied to the center of gravity of the liquid. Loading conditions of liquid up to 98 % were considered in the calculation of the maximum liquid height. The heat ingress warmed the LNG, which caused it to exceed its boiling temperature. The calculation of vapor pressure was described by the material and energy balance equations. Dynamic simulation about the pres-sure behavior was conducted using a commercial software. The thickness of the vessel shell was determined based on the allowable stresses and the membrane theory. To reinforce the shell under the internal pressure, glide type stiffeners were used. A strip method was used to compute the adequate size of the stiffener. The minimum distance of the parallel plates that support the deflection of the whole structure was calculated by the proposed equations. The analytical results for the design of the storage vessel were compared with those obtained by the numerical method using FEA.