API 620 is a standard American Petroleum Institute (API)

API 620 is a standard developed by the American Petroleum Institute that covers the design and construction of large, welded, low-pressure storage tanks. It’s often used alongside or compared with API 650, but it serves a different purpose.

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Key Characteristics:

1. Pressure Range:

   • Designed for internal pressures up to 15 psig (1.03 bar)

   • Typically higher than what API 650 allows (which is ≤ 2.5 psig)

2. Temperature Range:

   • Can handle low-temperature service (as low as −325°F / −198°C), including cryogenic liquids

3. Tank Shape:

   • Vertical, cylindrical, above-ground tanks

   • Flat or domed bottoms

   • Flat, cone, or dome roofs

4. Materials:

   • Carbon steel and austenitic stainless steels

   • Designed with considerations for brittle fracture at low temps

5. Welding & Inspection:

   • Strict welding procedures

   • Radiographic or ultrasonic testing for welds

   • More stringent NDT (non-destructive testing) than API 650

📐 Applications:

API 620 is used for...Not used for...

LNG and cryogenic liquidsAtmospheric tanks

Liquefied gasesHigh-pressure tanks

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