Size of Used Oil Tank

A. To proceed a design for storage tank, you are requested to follow up the following calculation in accordance with API 650:

3.6.3 Calculation of Thickness by the 1-Foot Method

3.6.3.1 The 1-foot method calculates the thicknesses required at design points 0.3 m (1 ft) above the bottom of each shell course. Appendix A permits only this design method. This method shall not be used for tanks larger than 60 m (200 ft) in diameter.

3.6.3.2 The required minimum thickness of shell plates shall be the greater of the values computed by the following formulas:

In SI units: t_d = [4.9 D (H– 0.3) G]/ S_d + CA & t_t = [4.9 D (H– 0.3)] / S_t

where, t_d = design shell thickness, in mm,

t_t = hydrostatic test shell thickness, in mm,

D = nominal tank diameter, in m (see 3.6.1.1, Note 1),

H = design liquid level, in m,= height from the bottom of the course under consideration to the top of the shell including the top angle, if any; to the bottom of any overflow that limits the tank filling height; or to any other level specified by the purchaser, restricted by an internal floating roof, or controlled to allow for seismic wave action,

G = design specific gravity of the liquid to be stored, as specified by the purchaser,

CA = corrosion allowance, in mm, as specified by the purchaser (see 3.3.2),

S_d = allowable stress for the design condition, in MPa (see 3.6.2.1),

S_t = allowable stress for the hydrostatic test condition, in MPa (see 3.6.2.2).

B. To calculate tank capacity in m³, Q = 25 000 ton of oil x Oil specific Gravity

From which we can determine the tank diameter D by assuming tank height H: Q = (∏/4) D² x H (note : H is the design liquid level, that is mean the tank height can be more by at least 1 m approx.).

C. The tank can be fabricated from carbon steel material (not from stainless steel), using epoxy coating on tank interiors.

D. I think you need an experienced design engineer.