The basic structure of a large oil storage tank is composed of tank wall, tank top, tank bottom and tank accessories. The longitudinal welding seam of the tank wall ring plate of the oil tank is generally a butt joint, a circumferential welding seam, a sleeve type is generally used for medium and small-capacity oil tanks, and a large-capacity oil tank is generally a mixed type. The tank wall steel plate must meet the strength requirements and also the stability requirements. Generally divided into vertical vaulted oil tanks, vertical cone-top oil tanks, and spherical oil tanks. The structure is divided into two types: butt joint and overlap joint. The bottom plate of the vault oil tank generally has a two-sided three-knife structure. The middle part of the tank bottom plate is called the medium plate, and the edge part is called the edge plate. When the diameter of the oil tank is D<12.5m, the typesetting form composed of a rectangular middle plate and the edge is generally adopted. When D≧12.5, the typesetting form composed of a bow-shaped edge plate is adopted.