API 650 unanchored liquid-storage tanks design thickness

The factors affecting the "small breathing" loss of API 650 unanchored liquid-storage tanks are: 1. It is related to the change of temperature difference between day and night. The greater the change of temperature difference between day and night, the greater the loss of "small breathing"; on the contrary, the smaller the change of temperature difference between day and night, the smaller the loss. 2. It is related to the sunshine time of the oil storage tank. The longer the sunshine, the more the "small breathing" loss; otherwise, the less the loss.

Shell Stiffening Rings for Tanks That Contain Liquid
Internal or external shell stiffening rings may be required to maintain roundness when the tank is subjected to wind, vacuum, or other specified loads. When API 650 unanchored liquid-storage tanks stiffening rings are required, the stiffener-to-shell weld details shall be in accordance with Figure Q-1 and Q.3.5.2 through Q.3.5.5.
Three-plate laps or butt-weld junctions in tank bottoms shall be not closer than 12 in. from each other or from the butt-welds of the annular plates.
Bottom plates, other than annular bottom plates for a 9% or 5% nickel steel or stainless steel tank that contains liquid, may have a minimum thickness of 3/16 in. exclusive of any specified corrosion allowance.

This API 650 tank standard is designed to provide industry with tanks of adequate safety and reasonable economy for use in the API 650 unanchored liquid-storage tanks storage of petroleum, petroleum products. and other liquid products.