API standard 650 fixed roof tanks roof legs

In this project, an elemental area of API 620 oil storage tank wall is constructed of ASTM A516 Grade 55 steel plate subjected to a meridional unit force, T1, of 2620 lbf/in. tension and a latitudinal unit force, T2, of 2880 lbf/in. compression. The meridional radius of curvature, R1, is 132 in., and the length of the normal from the surface to the axis of revolution, R2, is 409 in. The joints in the wall are spot-radiographed, double-welded butt joints, and no corrosion allowance is required.
The problem in this example is to graphically find the minimum thickness of tank wall required for the given conditions (see API 620 tank standard 5.10.3.3).
Solution: As determined from Table 5-1, the maximum, allowable tensile stress value, Sts, for ASTM A516 Grade 55 steel plate in simple tension is 16,500 lbf/in.2. Since the compressive stress is latitudinal, the governing value of R for this situation is R1, or 132 in.

API 650 storage tank, double-layer oil tank environmental protection advantages: ordinary single-layer steel API standard 650 Fixed roof tanks oil tank is corroded by underground water and gas and electrolytic corrosion because it is buried underground all year round. The API 650 tank has a double-layer structure with a gap of 0.1 mm. The API standard 650 fixed roof tanks outer layer of FRP ensures that the leakage will not directly leak into the soil and water source.

Generally, external environment corrosion should be considered before design and construction of API standard 650 fixed roof tanks and so on storage tanks. The corrosion on the outer surface of storage tank is often worse than that on the inner surface. Especially in the chemical industry area, there are often acid fog, alkali or salt dust in the atmosphere. These impurities form an active corrosive medium with dew or steam and oxygen in the atmosphere. The corrosion of the external environment of the storage tank shortens the maintenance period of the storage tank, even causes the storage tank to be scrapped in advance, which affects the normal operation of the storage and transportation.