If you are preparing a design/build specification for a tank you must consider what is going on inside the tank when making this decision. If vapor space corrosion is a problem you may want to minimize what may corrode. In that case a dome roof is the way to go.
If that is not a...
Have you done Section VIII, Div. 1 calcs. for vacuum? I assume you have the design information on the head configuration and material. If so the first step is to do regular code calculations. If the head itself is not good for the vacuum conditions to my knowledge there is no Section VIII...
API 650 is generally recognized as the reference code for flat bottom cone roofed tanks. You can analyze all elements using Compress or some other engineering design program. I would be very careful about making vacuum assumptions particularly for an API tank. I have been in the tank and...