How calculare a vessel coil under vaccum conditions.

[seamantgn]

I have to design a vertical vessel with a half coil in part of the shell and head.
Process data indicate 10 bar and FV forma the vessel and coil.
The design code it's Asme VIII Div 1.
For internal pressure in vessel and coil there are equations to have vessel thickness due to both pressure. And the coil thickness.
For vacumm in the vessel and pressure in the coil the same. Question: for vessel thickness due to the coil i must sum coil pressure plus vaccum value?
But if are pressure in the coil and vaccum in the vessel it don't have a equation for the vessel thickness due to the vaccum. I can use the equation used when there was pressure in the coil? Using the vessel pressure plus the vaccum modifing a constant of the equation.
The software don't accept negative values for the coil.
Also i think the vessel thickness due "vaccums" will be bigger in the case of the vessel vaccum. Bit not sure.
Are there other code who has equations for these cases?
In the case of half pipe coil with vaccum i can use the general formula of the pipe por shel under external pressure?

Somebody can give me a hand

Regards

 

[seamantgn]

Sorry i have problems with the language configuration.
I reffered what about when i have vaccum in the coil and pressure in the vessel.