API 620 External pressure

[Heyner]

I have a datasheet of a tank to be designed per API 620 standard, and it shows +700mm H2O and -100mm H2O as design pressures. Reading scope at API 620 (1.2.2) I can find 15 psi as maximum internal pressure, no clue about external pressure. I remembered then that API 650 address for a maximum 1 in H2O as external pressure (25 mm H2O).

Has API 620 any direction for external pressure? -100mm H2O seems to me to be a high external pressure for this kind of tank (D=3050mm, H=3660mm).

I’m receiving comments.

 

[JStephen]

I was thinking that API-620 had a statement as to minimum vacuum allowable. I don't think that vacuum would be much of a problem on a tank that size.

Anyway, the new Addendum 4 of API-650 does address vacuum design. It's the last appendix in the standard.

Note that your pressure range falls within the scope of App. F of API-650, so the tank could be built to it, owner permitting.