Higher Operating Pressures in Shop Fabricated Tanks

[merton]

As the use of gas blanketing systems increases I am receiving more inquiries for higher operating pressures for shop fabricated storage tanks. The most common sizes are 750 BBL (15'-6" diameter, 1000 BBL (17'-3" diameter) and 2000 BBL (23'-6" diameter) tanks to be supplied with operating pressures ranging from 8 oz to 16 oz.
I realize that the API 650 code in basically for larger storage tank than these, but can the same principles in this code be applied to smaller storage tanks in order to meet customers requests. Some of the principles I refer to are anchoring and compression ring design.

Any information on this subject would be greatly appreciated.

 

[IFRs]

Once you exceed API 650 pressure (2.5 psi), you are best served by using API 620. Is the 8 oz to 16 oz a pressure per square inch, per square foot, or what? API 650 works for small tanks as well as large - there is no diameter limit that I know of. I would be cautious when using API 650 to design a frangible shell-to-roof joint as the failure mechanism is quite different for small tanks such as yours.

 

[merton]

All the pressures I had indicated in the original post are per square inch.

Thanks to IFRs for the reply.

I agree that the frangible characteristics set down by API 650 are difficult to meet on small tanks. For inbreathing and outbreathing I would probably use pressure vacuum relief valves and emergency pressure relief valves sized as per API 2000.