API 650 Storage Tank 1-Foot method equation

[aqeel14]

Hello,

Any guide on why in API 650 tank formula for 1-foot method doesn't consider vapor space pressure.
Like we have it in BS 2654.

Thanks,

 

[Geoff13]

When the pressure is low (as defined in 1.1.1) then it is ignored.

However for larger pressures you must use Annex F, which does add on the vapour space pressure (see F.2.1).

 

[aqeel14]

Thanks Geoff13.