Seismic design for API Std 650 self-anchored tanks
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.
Under the same sealing effect, the internal floating roof tank of API 650 oil storage tank can further reduce the evaporation loss compared with the API Std 650 self-anchored tanks External floating roof tank. This is due to the shielding of the fixed roof and the gas layer between the fixed roof and the internal floating plate, which has more significant heat insulation effect than the double disc floating roof of the API Std 650 self-anchored tanks external floating roof tank.
In 2014, we offered 175 ton Cold rolled stainless steel plate to Thailand. The API Std 650 self-anchored tanks products are from TISCO. Here is the MTC that we offered to customer. We have our own quality team. Our quality team will inspect every order before shipment for customer. Normally, we will test the chemical composition, thickness, width, and length. Here are some pictures for last inspection.
}Generally, external environment corrosion should be considered before design and construction of API Std 650 self-anchored 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.
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