API 650 OIL STORAGE TANK DESIGN CALCULATION

API 650 is a standard developed by the American Petroleum Institute (API) for the design, fabrication, erection, and inspection of welded steel oil storage tanks. This standard covers tanks with a diameter greater than 30 feet (9.144 meters) and capacities up to 500,000 barrels (79,500 cubic meters).

To design an oil storage tank based on API 650, you will need to consider the following steps:

1. Determine the tank dimensions:

   • Volume (V): The volume of the tank is based on the desired storage capacity (usually given in barrels or cubic meters).
   • Diameter (D): API 650 requires the diameter of the tank to be greater than 30 feet (9.144 meters).
   • Height (H): Calculate the tank height based on the volume and diameter, using the formula V = π(D/2)^2 * H.

2. Design the tank shell:

   • Shell thickness: Calculate the minimum required shell thickness, taking into account the specific gravity of the stored liquid, the hydrostatic pressure, and other factors.
   • Shell courses: Divide the height of the tank into multiple shell courses, with each course having a specific thickness.

3. Design the tank roof:

   • Select the type of roof: API 650 allows for various types of roofs, such as fixed cone roofs, floating roofs, and external floating roofs.
   • Calculate the thickness and material for the selected roof type.

4. Design the tank bottom:

   • Determine the minimum thickness and material for the tank bottom, based on the liquid weight, corrosion allowances, and other factors.

5. Design the tank foundation:

   • Select an appropriate foundation type, such as ringwall, slab, or pile-supported foundation.
   • Calculate the foundation dimensions and required materials.

6. Design the tank appurtenances:

   • Include necessary appurtenances, such as manways, nozzles, vents, and ladders, in compliance with API 650 requirements.

7. Perform a wind and seismic analysis:

   • Assess the tank's structural integrity and stability under wind and seismic loads, in accordance with API 650 and local building codes.

8. Compile fabrication and erection specifications:

   • Create a detailed set of specifications and instructions for fabricating and erecting the tank, following API 650 guidelines.

9. Inspection and testing:

   • Ensure that the tank is properly inspected and tested during and after construction, in compliance with API 650 requirements.

Please note that this is a general overview, and for a complete and accurate design, it is crucial to consult the full API 650 standard, applicable local building codes, and engage the services of a qualified engineer.