Could this be what you want?
API Std 2510 Design and Construction of Liquefied Petroleum Gas Installations (LPG)
Another reference you may want is
API Publ 2510A Fire Protection Considerations for the Design and Operation of Liquefied Petroleum Gas (LPG) Storage Facilities
Poseilus: You want quick and dirty? Call several "previously owned" equipment vendors and ask what they have. Or, call a big new vessel manufacturer and ask for the size of several recently built tanks.
What are you asking ??.....Are you asking about LPG tanks or the tank facility ??
Design Requirements and other information about LPG tanks can be found in NFPA-58.....Tanks for USA service are to be certified ASME Section VIII Pressure vessels.
try this website and tell us more about your application