The study of the crack apparition and propagation on a 60 cubic meters steel tank

Abstract

International Association Of Classification societies inspect every year all safety systems from the LNG/LPG ships, regarding the storage tanks. The cargo in the tanks of gas carrier is partially liquid and partially vapour in normal condition. However, when the tank structure collapses, the vapour tries to escape or leak through the opening, resulting in decreasing the pressure inside the tank. These drastic lowering of pressure inside the cargo tank results in rapid boiling of liquid and increase in vapour formation. The pressure of the escaping vapour becomes very high and leads to a shock wave or explosion in presence of a fire source, completely destroying the tanks structure and surrounding areas. This matter determined the beginning of the study about the cracks that appear on a tank that is 10 meters long, has 3 meters in diameter and is made of steel plates with a 45 millimetres thickness.