According to the installation sequence of LNG atmospheric storage tank, the bottom surface should be anticorrosive before the bottom plates are installed (50mm width area within lapping range is left unbrushed).
Before the bottom plates are laid, a crosshair should be drawn on the surface of the accepted foundation. When the drawn lines deviate from lines marked on the drawing to a large degree (but within the allowed range), they should be adjusted to have the minimum deviation. The bottom plates should be laid from the center to the periphery of the tank according to the layout drawing. First lay a piece of plate in the center, its position should be accurate, there should be no vertical and horizontal rotating error. The horizontal error of the central axis should be less than 2mm. When the plate is laid, make sure the crosshair on the ground is printed onto the plate, then mark the lines and the center point on the plate to be clear.
The welding of bottom plates shall be positioned welding, with the help of fixtures. The same welding materials shall be used for positioned welding, and arc initiation and arc extinguishing shall be in the groove or on the welding path. The length of each section of positioned welding should not be less than 50mm.
For the welding of bow edge plates, the center plates shall be placed on the top of the bow edge plates. The lap width required by the design should be 40mm, and the allowable deviation is ±5mm. The maximum gap between the two plates at the lap joint should be less than 1mm. In the process of plate-placing, the short seam of the plate end should be spot welded first. The seam between the center plate and the side plate will be welded after the bottom plate is installed.