After the tank body is spliced and welded, the weld seam is definitely not round, so the tank body should be put back on the plate bending machine for rounding operation; In addition, prepare an inner circular arc template, and measure it continuously when rounding, without rounding. If the tank is large in diameter and thin in wall thickness, its own weight will lead to deformation and roundness when it is in the tank bungalow. In the final measurement, make sure that the axis of the oil tank is perpendicular to the ground to check its roundness.