Most regions and countries in Europe, America, and globally widely adopt standards such as API 650, API 620, API 12D (American standards) and BS EN 14015 (British standard) for the design, construction, and installation of oil and storage tanks. These belong to the API standard series—API stands for the American Petroleum Institute, founded in 1919 as the first national commercial association in the United States. It is one of the earliest and most successful standard-setting organizations worldwide. A key mission of API is to standardize equipment used in the petroleum and natural gas industries to ensure safety, reliability, and interoperability. Developing and harmonizing standards is one of API’s earliest and most successful initiatives. API standards primarily specify equipment performance and, in some cases, include design and process specifications. Their standardization efforts cover areas such as petroleum production, refining, measurement, transportation, sales, safety, fire protection, and environmental regulations, with information technology standards extending to petroleum and natural gas industries, communications, and IT applications.

Application of API 650
As stated by the American Petroleum Institute, the fabrication and installation of above-ground welded steel storage tanks are commonly applied in industry. Typically, storage tanks installed at industrial sites in the United States are constructed according to API 650, API 620, and API 12D standards. These standards classify and guide the design, fabrication, and installation of above-ground welded steel tanks. All three API standards involve on-site fabrication and installation. Below is an overview of tank design and construction according to American standards:

1. API 650 Tanks – Construction Standard
   The most widely adopted global standard for tank construction and procurement is API 650, translated as “Welded Steel Tanks for Oil Storage.” API 650 tanks are commonly used for storing petroleum products such as gasoline, diesel, chemicals, and production water. Tanks built to this standard are widely deployed in refineries, terminals, pipelines, and production facilities across the United States. API 650 specifies detailed requirements for tank design, fabrication, welding, inspection, and installation procedures.

2. API 620 Tanks – Construction Standard
   The Chinese translation of API 620 is “Design and Construction of Large, Welded, Low-Pressure Storage Tanks.” This standard provides specifications for the design and construction of large, welded steel low-pressure storage tanks. API 620 tanks operate at temperatures up to 250°F or lower, with an operating pressure exceeding 2.5 psi but less than 15 psi.

3. API 12D Tanks – Construction Standard
   API 12D is translated as “Field Welded Tanks for Storage of Production Liquids.” It specifies requirements for field-welded tanks used in storing production liquids or petroleum and is one of the three most well-known standards. API 12D applies to on-site installed storage tanks, specifying tank dimensions, storage capacity, fittings, and testing requirements. By establishing fixed sizes and requirements, API 12D eliminates the need for additional engineering, effectively reducing the cost of tank construction.