BASIC COMPARISON OF SELECTED STRUCTURAL STEEL STRENGTH INFLUENCE ON TOTAL WELDING FABRICATION COSTS OF OIL STORAGE TANKS

Uses of lighter, stronger, reliable and cheaper welded steel structures are constant trends. There is a various industrial application where structural steels with higher strength replace conventional low strength structural steels. This paper will outline basic comparison of three type of structural steel selection influence on total welding fabrication costs of atmospheric oil storage steel tanks (design and fabrication according to API 650). However, there are a number of parameters which may influence welding fabrication costs, as well as different company’s experiences, and therefore provided calculation assumptions in this paper do not have any intention to underestimate them. While considering typical types of structural steels, i.e. S235, S275 and S355 (acc. to EN 10025) the basic parameters which influence its selection on total welding fabrication costs are described. In particular, paper will outline selection influence related to size of oil storage tank. In addition, only one particular type of tank shall be evaluated, i.e. oil storage tank with fixed roof within its size limits applicable for oil industry. While considering minimum required thickness of shell structure as defined in API 650 according to selected structural steel, and almost non-affected thickness of roof and bottom, the main influencing parameter, i.e. sizes of tank shell butt weld joints shall be evaluated. In all cases, the same possibly applied welding technology shall be considered, while considering appropriate filler material strength class. Finally, range of total welding fabrication costs savings due to the use of stronger structural steel shall be outlined in relation to oil storage steel tank size, as well as used spreadsheet calculation.