Dear All,

Pls refer to the roof specification parameters menu of the Coade Tank - General Roof Specs - Net Area at Roof/Shell Junction (A)

Coade Tank software send us to Appendix F and the related formula is as below (acc. to API 650 2009 Appendix F.5.1)

A = 220(D^2)x(Pi-0.08 ti)/(Fy x Tan0)

D : Diamater
Pi : Internal Design Pressure

My question is that if the internal design pressure is zero (athmospheric tank) then Junction Area (A) will be minus value. Is there any calculation method for the Junction Area (A) ?

Thanks for the help

eugeneee,

Any time you get a negative term there, it means the internal pressure effect is less than the weight of roof plates.
Under Figure F-1—Appendix F Decision Tree, you are in case
Does internal pressure exceed weight of roof plates?
IF
No
GO TO
Basic Design

The basic design includes dimensional provisions for the elements participating to that area.
See
5.10.2.2 Roof plates shall have a minimum nominal thickness of …
And
5.6.1.1 … the shell thickness shall not be less than the following….
And
5.1.5.9 Roof and Top-Angle Joints, point e
e. Except … tank shells shall be supplied with top angles of not less than the following sizes….

So there is an inherent minimum area required by API650 Basic Design.
You would check if it is adequate- e.g. for loads as wind roof uplift and wind on shell, if you construct a model to calculate such things.
Such calculation is out of API 650.

Best regards.