1 reply to this topic

[victorvikram]

Dear All,

 

I was going through API Std 2000 and EN14015 on Self-Supporting Cone Roof. In API Std.2000, the following rules shall be met:

 

a) theta <=37degrees (slope 9:12)

theta >= 9.5 degrees (slope 2:12)

 

To calculate theta, two formulas are provided that are:

 

Min. thickness = [Nominal diameter of tank shell (m) / 4.8 sin(theta)] >= 5mm

Max. thickness = 12.5mm

 

theta is defined as angle of the cone elements to the horizontal in degrees.

 

In EN14015, for Self-Supporting Roof, the slope provided is 1:5 (unless otherwise specified).

 

Which one should I follow?

 

The second part is assuming I have a FRT of 73.0m in diameter. If I were to calculate theta with the assumption that the thickness is 5mm, the formula shall look like:

 

73.0m / 4.8 sin(theta) = 5mm

sin(theta) = 3.042

(theta) = arcsine (3.042)

 

Obviously, I am unable to calculate theta as the range is between -pi/2 to pi/2. Is my calculation wrong?

 

Appreciate your advice on this matter.

 

Regards,

Victor

[kkala]

1.Let us see the formula of API 2000 as: required thickness t = D/(4.8*sinθ), where 9.5°≤θ ≤37°. But also it shall not be t<5 mm, nor t>12.5 mm.

-For cone roof tank with D=73 m, roof thickness t=15.2/sinθ mm, ranging between 25.3 and 92 mm. So t=12.5 mm (this is the maximum)

-For cone roof tank with D=9 m, t=1.875/sinθ, ranging from 11.4 mm (θ=9.5°) to 5 mm (θ=22° - 37°).

-EN14015 specifies slope 1:5, that is tanθ=0.2, θ=11.3°, unless otherwise specified. Roof thickness would be determined somewhere.

One can follow the applicable code, API 2000 or EN14015.

2. Floating roof has not slope, it probably concerns a typo. If it was a cone roof tank, t=12.5 mm, as explained above.

3. Having no experience on such calculations (but seen no response so far), comments are welcomed.