API standard 650 storage tank lap-welded bottom joints

In this project, a cylindrical tank 62 ft 6 in. in diameter is designed for an internal pressure of 4 lbf/in.2 gauge in the vapor space. The plate material is ASTM A131 steel with appropriate grades for different plate thicknesses in accordance with Table 4-1 for a design metal temperature less than 65°F but not less than 25°F. No corrosion allowance is required for any portion of the tank. The top course of the butt-welded cylindrical sidewall is 1/4 in. thick. The roof is a single lap-welded spherical dome with an internal radius of 50 ft and a thickness of 1/4 in. The maximum design liquid level is 6 in. below the plane of the juncture of the tank API standard 650 storage tank roof and sidewall.

This specification, in conjunction with API 650 Standard, prescribes minimum standards for the API standard 650 storage tank design, supply, fabrication, erection, and testing of field erected welded steel storage tanks complete with accessories as specified herein and as shown on attached Datasheets and/or Drawings.

Requirements for prefabrication of the top of large vertical API standard 650 storage tank: The prefabrication of the tank top shall be prefabricated in blocks according to the drawings. Pay attention to the spacing of the welds after installation when setting out the material. Reinforcing ribs should be formed and inspected with an arc-shaped template. When a single top plate needs to be spliced, butt joints should be used. The forming of a single top plate should be welded between the reinforcing ribs and the top plate on the mould. After forming, check with an arc-shaped sample plate, and the gap should not be greater than 10 mm.