Design Pressure for Uplift in API 650

[Clamont]

When calculating the uplift loads for overturn moment calculations (sect 5.12) it states that P should be calculated from Appendix F as opposed to the actual design pressure of the tank. If the tank is small however P calculated in F.4.1 can be incredibly high and distort the calculations somewhat as that pressure will never be met. Do you still use this calculation as the input for the uplift requirements or use the actual design pressure of the tank perhaps set by the Pressure Vacuum Valve whic is a more realistic design pressure?

 

[IFRs]

I'm not sure where you are seeing this requirement - can you be more specific?

 

[fabtank]

The equation in F.4.1 is for establishing the maximum design pressure of a tank that is already constructed or designed.
Use you're actual design pressure for uplift calculations.

 

[JStephen]

In the tables for uplift loads, it says "See App. F" for P. However, Appendix F gives maximum values of P, but does not require that P be set at the maximum values calculated.

 

[Clamont]

Many thanks Fabtank however why does it state see Appendix F if you are supposed to use the actual design pressure and not that calculated by F.4.1 which is P?

IFRs,

I am referring to table 5-21 Uplift Loads to determine the Net Uplift Formula.

P = design pressure in inches of water column (see Appendix F).

 

[JStephen]

Design pressure is specified by the purchaser per Line 7 in the data sheet, see page L-14.
The decision tree in Figure F-1 tells you how to treat that design pressure, whether it falls under App. F or not, and if so, which part of App. F.
The wording in the table 5-21 could probably be improved to clarify this. Appendix F is used for pressure design, but the design pressure is not determined by Appendix F.