API 650 Tank Design Pressure

[napster385]

Good day!

How is the design pressure of an atmospheric storage tank determined based on the requirements of API 650?

 

[fegenbush]

It is determined by the owner/end user to meet the process requirements, inflow/outflow requirements, blanketing gas, vapor pressure of the contents, and good old "that's the way we've always done it."

 

[IFRs]

What fegenbush said plus: API 650 limits the design pressure to the weight of the roof plate unless you use Appendix F in which case it is 2.5 psig.

 

[napster385]

If the client only specifies that the tank is designed to atmospheric as per API 650, what will be the appropriate data to be reflected in the design pressure in the nameplate of the tank?

 

[IFRs]

"atmospheric"

 

[fegenbush]

napster385,

Do not forget that, even if the client specifies atmospheric, the minimum external pressure is 1" of H₂O (unless Appendix H circulation vents are present). I have had several clients question me about this, but it is right there in 5.2.1.b