Detailed Comparison: API 650, API 620, and EN 14015
When designing industrial storage infrastructure, selecting the correct engineering code is the most critical decision for safety and compliance. While API 650, API 620, and EN 14015 all govern the design and fabrication of welded steel tanks, they serve distinct operational needs based on pressure, temperature, and regional regulatory requirements.
1. API 650: The Atmospheric Benchmark
API 650 is the global industry standard for welded, vertical, cylindrical, aboveground storage tanks operating at atmospheric pressure [1.1.1, 1.1.3].
Primary Focus: Atmospheric storage tanks designed to hold liquids at ambient temperatures [1.1.3, 1.1.4].
Operating Pressure: Up to 2.5 psig [1.1.4, 1.1.5].
Best Used For: Crude oil, refined petroleum products, biofuels, and water storage in refineries, terminals, and tank farms [1.1.4, 1.1.5].
Why It’s Popular: It offers a balance of safety, structural predictability, and cost-effectiveness, making it the default choice for general bulk liquid storage [1.1.4].
2. API 620: Low-Pressure & Cryogenic Service
API 620 serves as the standard for large, welded, low-pressure storage tanks that exceed the limitations of API 650 [1.1.1, 1.1.3].
Primary Focus: Tanks requiring higher internal pressure or specialized low-temperature/cryogenic service [1.1.1, 1.1.4].
Operating Pressure: Typically up to 15 psig (though designs can go higher) [1.1.1, 1.1.3].
Best Used For: Liquefied Natural Gas (LNG), Liquefied Petroleum Gas (LPG), and volatile chemicals that must be stored under pressure or in refrigerated/cryogenic states [1.1.1, 1.1.4].
Engineering Complexity: Requires stricter non-destructive testing (NDE), enhanced welding protocols, and rigorous impact testing of materials to ensure integrity at low temperatures [1.1.1, 1.1.4].
3. EN 14015: The European Standard
EN 14015 is the European equivalent to API 650, governing the design and manufacture of site-built, vertical, cylindrical, flat-bottomed, welded steel tanks for liquids at ambient temperatures and above [1.2.1, 1.2.4].
Primary Focus: Harmonized European standard for atmospheric storage tanks [1.2.2].
Operating Pressure: Designed for low internal pressures similar to API 650 [1.2.2].
Best Used For: Crude oil, petrol, chemicals, and water storage within European jurisdictions [1.2.2].
Engineering Note: While structurally similar to API 650, it incorporates European design codes and material standards, making it the mandatory choice for many European facilities governed by local directives (like PGS 29) [1.2.2].
Comparative Selection Matrix
Parameter | API 650 | API 620 | EN 14015 |
Standard Origin | USA (API) | USA (API) | Europe (CEN) |
Pressure Class | Atmospheric (≤ 2.5 psig) | Low Pressure (≤ 15 psig) | Atmospheric |
Temp Range | Ambient | Cryogenic to 250°F | Ambient and Above |
Primary Use | General Petroleum | LNG/LPG/Cryogenic | European Industrial |
Material | Carbon/Stainless Steel | Carbon/Ni/SS Alloys | Carbon/Stainless Steel |
Frequently Asked Questions (FAQ)
Which standard should I use: API 650 or EN 14015?
If you are operating in North America or following global oil/gas practices, API 650 is the standard. If your project is located in Europe or must comply with specific EU directives (like PGS 29), EN 14015 is the mandatory standard for site-built atmospheric tanks [1.2.2].
Can API 650 tanks handle cryogenic temperatures?
No. API 650 is designed for ambient temperatures. For cryogenic storage (e.g., LNG), you must use API 620, which includes specific material toughness requirements and impact testing to prevent brittle fracture at sub-zero temperatures [1.1.4].
Are there significant structural differences between API 650 and EN 14015?
While they are functionally similar (both handle atmospheric, flat-bottomed storage), they utilize different design codes, material specifications, and regulatory annexes [1.2.2, 1.2.3]. EN 14015 is fully integrated with Eurocodes, whereas API 650 is a self-contained American standard.
Why is API 620 more expensive to build?
API 620 tanks require higher quality control, mandatory radiographic testing of all vertical and horizontal butt welds, and more rigorous material certifications due to the higher pressure and low-temperature risks [1.1.1, 1.1.4].
