External Design Pressure of API 650 Tank

[MOHAMMED89]

Dear All,

I need your advice on how to calculate the external design pressure for a API 650 tank, tank details are as follows:-

Tank Size - 30m (dia) x 25m (height)
Service - Aviation Fuel
Internal Design Pressure - 13 Kpag.
Remarks - The internal design pressure is finalized based on the nitrogen blanketing positive pressure.
Roof type - Fixed Cone Roof

what will be the external design pressure ?

Thanks in advance

 

[IFRs]

You all are missing my point and perhaps my poor choice of example is making it worse. Of course temperature change affects pressure inside a closed vessel. That's not the point. My point is that the vapor pressure of fuel oil does not represent an increase in atmospheric pressure inside the tank, all other things being equal.

A blanketing system does not need to overcome the vapor pressure of the oil in this case. The pressure inside the tank is atmospheric despite the partial vapor pressure of the fuel. The OP asked about the vacuum design side and I got us all mired in the pressure side. My sincerest apologies.