API 620 vs API 650 storage tanks: What to Choose When

The oil & gas industry largely deals with petroleum products, gasoline & other chemicals. To contain such hazardous materials, it requires specialized storage tanks that are up to the job and adhere to American Petroleum Industry (API) standards.

The national trade association for the oil and natural gas industry has established standards for the design and construction of field assembled storage tanks. API 620 and API 650 models are the most commonly used to withstand the varying pressures of the liquids.  

Read on this article to explore factors that will help you decide between API 620 and API 650 – which one makes the most sense for you.

API 650 specifies guidelines for design, fabrication, erection, materials, construction & inspection of above-ground, open or closed-top, cylindrical storage tanks in various sizes and capacities. The welded tanks for Oil storage normally function in the atmospheric pressure range ((not more than the roof plate weight). 

API 620 covers the design and construction of large storage tanks in the low-pressure zone on an elevated or flat bottom on which to store it. These tanks are built from carbon steel, austenitic stainless steel, and nickel alloys.

Given below are the key differences between API 650 and API 620

API 650 Tank: Ground-Supported Bottom, Open or Closed Roof

API 620 Tank: A single, vertical, central axis of revolution

API 650 Tank: Both

API 620 Tank: Field Erected

API 650 Tank: Any

API 620 Tank: Larger than 300 ft

Temperature Range: 

API 650 Tank: -40 o F to 500 o F 

API 620 Tank: -325 o F  to 250 o F

Maximum Pressure: 

API 650 Tank: Tanks should contain only liquids up to 2.5 PSIG (pounds per square inch gauge) or 17.2 Kpa

API 620 Tank: Safe for low-temperature liquids, gases, and vapors up to 15 per square inch (PSI) of vapor/gas storage

Materials used for Construction: 

API 650 Tank: Carbon Steel, Austenitic Stainless Steel, Duplex Stainless Steel, Aluminum

API 620 Tank: Carbon Steel, Austenitic Stainless Steel, Nickel Alloys 

API 650 Tank: Oil, Gas, Chemical, Water, and Biofuels storage. Tanks are usually found in Refinery tank farms, Terminals, Pipelines, and other process facilities that use these tanks.

API 620 Tank: It is used for products that have high internal pressure such as liquefied natural gas (LNG) tanks or Cryogenic tanks.

With this information in mind, your choice of model will depend on your plant’s specific pressure and temperature requirements. Choosing the right industrial equipment engineering services provider can create a major impact on the way your storage facilities functions in the years to come.