API 650

[Adam001]

In API 650 item 5.1.5.9 e , there is "Roof-to-shell connection details per Figure F.2 are permissible provided that the design effective area (crosshatched
section) is greater than or equal to the design effective area provided by the minimum top angle size listed above " , I know how to calculate the available area according to F.2 but I don't know how to calculate required area or minimum area according to this wording , the code doesn't refer to equations but in appendix F item F.5.1 there is an equation but for max pressure only so I got confused so how can I calculate required area ?

 

[JStephen]

Assume the minimum top angle size specified in API-650, with your roof and shell thickness, and calculate the effective area per the details in Figure F.2.
Then calculate the effective area of whatever you propose to build.
That second area needs to be at least as large as the first in order to omit the top angle.

 

[Adam001]

ok thank you but what is the area in item 5.10.2.6 (5) and item F.5.1 ?

 

[JStephen]

The wording in 5.1.5.9e allows you to use alternate roof-shell details as shown in Annex F provided you furnish as much area as you would with a standard top angle.

Depending on the details, there are other separate area requirements for pressurized tanks (Annex F), for vacuum tanks (Annex V), for tanks with self-supporting cone and umbrella roofs, and for frangible connection tanks.

5.10.2.6(5) is the maximum area that you can have for a roof designed as frangible. If not frangible, you need an emergency vent. This may or may not apply to your tank.
F.5.1 is the minimum area required required for a pressurized roof. This may or may not apply to your tank.

 

[Adam001]

This was very helpful thank you