Gasoline Storage Tank

Gasoline storage Tank Umair saeed Roll No. 56 Final year Chemical engineering department

Storage of Gasoline

After the process completion, the final stage is the design of a suitable storage tank.

Storage tank

Pressure Pressure vessel vessel A pressure vessel is a closed container designed to hold gases or liquids at a pressure different from the ambient pressure. For the storage of volatile liquids, internal pressure vessel is used as a storage tank with an internal floating roof. Internal floating roof is used in case we have a volatile liquid. This helps in reducing the loss of vapours. The deck in internal floating roof tanks rises and falls with the liquid level. Contact decks can be: •aluminium sandwich panels •fibre glass reinforced polyester (FRP) •pan steel decks floating in contact with the liquid Floating roof

Shape Shape of of pressure pressure vessel vessel Pressure vessels may theoretically be almost of any shape e.g. •Spheres •Cylinders •cones A common design is a cylinder with hemispherical end caps called heads. Theoretically, a sphere would be the optimal shape of a pressure vessel. But A spherical shape is difficult to manufacture more expensive Difficult to erect so most pressure vessels are cylindrical with 2:1 semielliptical heads or end caps on each end.

INTE RNA L FLO ATIN G ROO F TAN K

Internal view of an internal floating roof tank

Designing of internal floating roof storage tank

Collapse of a storage tank as a result of design fault

Design calculations Density of gasoline at 20 oC = 737.22 kg/m3 ρ1/ρ2 = [1 + c*T1]/ [1 + c*T2] *engineering measurement methods by T A Polak

ρ1 = [1 + 0.001(44.1)/1 + 0.001(20)] * 737.22 Density at 44.1 C = 754.63 kg/m3 for gasoline Volume for 66125 kg of gasoline = 66125/756.17 = 84.45 m3 10 % of liquid volume = 84.45*0.1 = 8.45 m3 Volume of storage tank = 82.45 + 8.45 = 92.895 m3 For cylinders, L/D = 2 *coulson and Richardson, Vol. 6 V = π/4 LD2 (:- L = 2D) 92.895 = π/2 D3 D3 = 59.138 m3 D = 3.89 m

Static pressure of liquid in the tank = pi = ρgh = 737.22*9.8*7.79 = 57610 N/m2 = 0.058 N/mm2 Now, Design pressure = 0.058 * 1.1 = 0.063 N/mm2 Now, design stress for carbon steel at 44.1 C = 135 N/mm2 *coulson and richardson vol. 6, table 13.2 Wall thickness = e = Pi*Di/2f – Pi e = (0.063 * 3.89*103)/ (2*135 – 0.063) e = 0.908 mm Adding corrosion allowance of 2 mm, as we have less corrosive environment, e = 0.908 + 2 e = 2.908 mm We will use Wall thickness e = 13 mm since we do have a low pressure, therefore wall thickness according to our calculation was less than the recommended one. And now we have to use recommended wall thickness according to coulson and Richardson . Vol. 6

Now, The pressure inside the tank is very low, Therefore, we use a torispherical head

For torispherical head, Rc = 3.89 * 103 mm Rk = 0.06 * Rc Rk = 0.06*3.89*103 Rk = 233.4 mm Cs = ¼[3 + √(Rc/Rk)]

*coulson and richardson vol. 6

Cs = 1.771

So, now e = PiRcCs/2Jf + Pi(Cs – 0.2) + C

*coulson and

Richardson vol. 6

e = 0.063*3.89*103*1.771 / 2*135 + 0.063(1.771 – 0.2) + 2 e = 1.607 mm + 2 mm e = 3.607 mm