API standard 650 fixed roof tanks overturning moment

The reticulated API standard 650 Fixed roof tanks shell API 650 storage tank is an important large-span space structure with high safety. Generally, the large-scale API 650 storage tank with a diameter of 21-60 meters or a volume of more than 20000 cubic meters should adopt the reticulated shell technology, which has been widely promoted and adopted in the world and China's petrochemical industry for more than 30 years.

Welding inspection of bottom plate of API standard 650 fixed roof tanks, vertical oil tank: During the fabrication and installation of API standard 650 fixed roof tanks, the bottom edge plate is welded first. According to the requirements of the technical standard, penetrant inspection is required for the weld of edge plate at the bottom of API standard 650 fixed roof tanks, that is, penetrant testing is required for each weld bead priming, filling and capping. In the process of testing, if any defect is found, it shall be repaired immediately. After the repair, the surface coloring penetrant test shall be conducted again until the test result is qualified.

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.

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