Tangential shear in API Std 650 flat-bottom oil storage tanks

Compared with the external floating roof API Std 650 flat-bottom oil storage tanks, the internal floating roof API Std 650 flat-bottom oil storage tanks has the advantages of protecting the floating roof from wind and rain and ensuring the quality of liquid storage under the floating roof. At the same time, because the inner floating plate is in the tank, there is no rain and snow load, so the central drainage pipe and escalator and other accessories on the floating plate can be omitted. In addition, under the same sealing conditions, the internal floating roof tank can further reduce the evaporation loss compared with the External floating roof tank.

Suggested Practice Regarding Installation of Low-pressure Storage Tanks
Access: All openings and accessories for tanks API Std 650 flat-bottom oil storage tanks constructed according to this standard shall be installed so that any periodic inspections required can be readily made.
Corrosion: When a tank bottom rests directly on the ground, a survey shall be made to establish the need for cathodic protection.
Drainage: All tanks in which water might accumulate under the hydrocarbon contents shall be provided with adequate drains that are suitably protected from freezing.

The working pressure of the low-pressure storage tank is greater than that of the atmospheric storage tank, but its pressure is less than 0.1MPa. API 650 petroleum storage tanks are classified according to their environment: Above-ground storage tank: refers to the bottom of the storage tank at the design elevation of API Std 650 flat-bottom oil storage tanks and above; the bottom of the tank is below the design elevation of +0.00 but not exceeding.