arto / vesselguy, I'm not familiar with Blodgett's Design of Weldments & Design of Welded Structures. What types of product service is this guide limited to? Surely, it can't be open-ended. The first thought that came to mind, when I read the question, was a structural code; however you're limited on product storage.
We STILL need to know what is going to be stored in this tank. Being offshore, I'm guessing it's either a potable water, cleaning solution, or fuel gas. I can't think of many other things that you would store in such a small tank, unless it's going to be used in the actual process of the platform; and the configuration of a circular tank will not work.
I have to disagree with you, when you say "there is no standard or code for this sort of things." The reason I'm going with UL-142 is because it IS an actual ANSI standard, and it covers flammable and combustible liquids.
Below is a copy of the Scope of UL-142:
1 Scope
1.1 These requirements cover steel primary, secondary and diked type atmospheric storage tanks
intended for noncorrosive, stable flammable and combustible liquids that have a specific gravity not
exceeding 1.0 in aboveground applications.
1.1.1 Each tank type may be fabricated in a combination of various shapes (cylindrical, rectangular or
obround) and orientations (horizontal, vertical) with or without multiple compartments, as covered in this
Standard.
1.2 These tanks are intended for installation and use in accordance with the Flammable and Combustible
Liquids Code, NFPA 30; the Standard for Installation of Oil-Burning Equipment, NFPA 31; the Motor Fuel
Dispensing Facilities and Repair Garages, NFPA 30A; the Standard for the Installation and Use of
Stationary Combustion Engines and Gas Turbines, NFPA 37; the Uniform Fire Code, NFPA 1; and the
International Fire Code published by the International Code Council.
1.3 The tanks covered by these requirements are fabricated, inspected and tested for leakage before
shipment from the factory as completely assembled vessels.
1.4 These requirements do not apply to tanks covered by the Specification for Field-Welded Tanks for
Storage of Production Liquids, API 12D; and the Specification for Shop-Welded Tanks for Storage of
Production Liquids, API 12F.
1.5 Deleted
1.6 These requirements do not cover special evaluations for resistance to hurricanes, tornadoes,
earthquakes, floods, or other natural disasters; or resistance to vehicle impact.
1.7 These requirements do not cover portable tanks intended for transporting flammable or combustible
liquids (such as shipping containers), or mobile use applications (such as mounted on a trailer). These
types of products are covered by separate UN, DOT, or equipment product standards.