API 650 cylindrical tanks roof columns

API 620 crude oil tank piping materials made according to ASTM A333 and A350 may be used at API 650 cylindrical tanks design metal temperatures no lower than the impact test temperature required by the ASTM specification for the applicable material grade without additional impact tests. For temperatures below those allowed by the ASTM specification, the following paragraph shall apply.

API 650 vertical tanks meet American Petroleum Industries (API) standards in design, material, fabrication, and testing of aboveground welded steel API 650 cylindrical tanksstorage tanks for use in industrial applications.

When the day light gradually decreases, the temperature of oil in the API 650 cylindrical tanks will also decrease, the evaporation speed will gradually slow down, and the pressure in the API 650 cylindrical tanks will also decrease. When the pressure in the API 650 cylindrical tanks is lower than the negative pressure rating of the breathing valve, the outside air is sucked into the API 650 cylindrical tanks through the open vacuum valve, which is the "suction" process of the oil tank.