API 650 covers atmospheric, ground-supported storage tanks rated up to 2.5 PSIG and temperatures between -40°F and 500°F. API 620 covers pressurized tanks rated up to 15 PSIG, built for cryogenic service down to -325°F, and used mainly for LNG. Which one you need depends on your pressure, temperature, and tank size requirements.

API, the American Petroleum Institute, sets standards for the design, fabrication, and construction of steel storage tanks used across the US oil and gas industry. Both API 620 and API 650 cover storage tank specifications, but the two standards apply to different pressure ranges, temperatures, and use cases. Let’s break down what each one covers, where they overlap, and where they differ.

Key Takeaways

• API 650 tanks handle pressure up to 2.5 PSIG and temperatures from -40°F to 500°F.
• API 620 tanks handle pressure up to 15 PSIG and temperatures from -325°F to 250°F, built for cryogenic and LNG service.
• API 650 has no tank size limit. API 620 only applies to tanks larger than 300 ft in diameter.
• API 650 tanks can be shop or field erected. API 620 tanks are field erected only.
• Both standards use the same construction materials and follow ASME Section 10 for welding certification.

API Standard 620

It is required to store API 620 on an elevated or flat bottom, depending on its configuration. A single vertical axis of revolution runs through the center of the tank. There must be a minimum of the 3/16-inch thickness of the material. API 620 also has the following characteristics:

• This product is made of carbon steel, austenitic stainless steel, and nickel alloys (low temperature only).

• ASME Section 10 stipulates the requirements for welding certification.

• A third party is not involved in the inspection.

• Inspection costs are the costs associated with nondestructive testing (NDE).

API 620 offers the following benefits

• Cryogenic tanks, like LNG, have high internal pressure, so API 620 is best suited for them.

• The container can be filled with gas or vapor at a higher pressure (15 pounds per square inch) than API 650 and a lower temperature (-325 degrees F to 250 degrees F).

• Liquids of any kind can be stored in them.

API Standard 650

The API 650 specifies tank designs, materials, construction, and testing requirements for above-ground, open and closed-top, cylindrical storage tanks for oil storage in various sizes and capacities, roughly equivalent to atmospheric pressure (not more than the roof plate weight).

Higher internal pressures are allowed if additional requirements are met. It only applies to tanks that cover the whole bottom evenly and tanks whose design temperatures are no greater than 200 degrees F. 3/16-inch material thickness is the minimum requirement. API 650 has the following characteristics:

• Construction materials include carbon steel, austenitic duplex stainless steel, and aluminium.

• Section 10 of the American Society of Mechanical Engineers (ASME) stipulates a Welding Certification.

• A third party is not involved in the inspection.

• NDE is the inspection cost.

API 650 provides the following benefits

• Oil, gas, chemicals, water, and biofuel can all be stored in these tanks.

• In addition to being able to store contents at a lower pressure (2 1/2 PSI), it can also store them at a higher temperature (-40 degrees F to 500 degrees F) than what is allowed by API 620.

• There is no limit to the size of the tank.

API 620 vs API 650: The Similarities

• Both standards of tanks serve as storage facilities.

• Both tanks are constructed from the same materials, such as carbon steel, austenitic stainless steel, and nickel alloys (low temperature only).

• The American Society of Mechanical Engineers (ASME), Section 10 stipulates the requirements for welding certification for both tanks.

• Neither tank is subject to Third-Party inspection, but a non-destructive inspection is required.

Want to know more about the capabilities of API standard 650 and 620? You can learn more about it here.

API 620 vs API 650: The Differences

Let’s know about the significant difference between API 620 vs API 650.

As for similarities, there are quite a few differences concerning various parameters between API standard 650 and 620. Therefore, let us check some essential parameters to highlight the critical differences between the two models.

Configuration of API 620 vs API 650

API 650 – The configuration is specified for the ground-supported bottom and open or closed roof. To achieve this configuration, the entire tank bottom needs to be supported uniformly.

API 620 – It is flexible to any configuration that is single centered. To achieve this, tanks of this type must revolve around a single vertical axis.

Uses/Industries

API 650—Gas, oil, chemicals, water, and biofuels are all stored here. Most welded steel tanks utilized in an industry follow API 650. Such tanks are found in refineries, pipelines, terminals, and other industrial facilities.

API 620 – API 620 is used for tanks that require high internal pressure, such as LNG tanks and cryogenic tanks.

Shop/Field Erected of API 620 and API 650

API 650 – Shop (Appendix J) or Field Erected

API 620 – Field Erected

Tank Sizes of API 620 vs API 650

API 650 Tanks – Compatible with any tank size

API 620 Tanks – Compatible only with tank sizes larger than 300 ft.

Temperature Range of API 620 vs API 650

API 650 – -40 Deg. F to 500 Deg. F

API 620 – -325 Deg. F to 250 Deg. F

Maximum Pressure of API 620 vs API 650

API 650 – 2.5 PSIG (pounds per square inch gauge) or 17.2 Kpa

API 620 – 15 PSIG

With this information in mind, we hope this article clarifies some of the critical differences between API 620 vs API 650 storage tanks. By considering the parameters mentioned above, you can decide which API model best suits your business needs for safe and reliable storage now that you know about API 650 and 620 difference. Do you need a custom quote for the design, fabrication, and welding of your storage tanks? Get in touch with Mechartes right away!

API 620 vs API 650: A Quick Comparison

FAQs:

1. What’s the main difference between API 650 and API 620?

API 650 covers atmospheric, ground-supported tanks rated up to 2.5 PSIG. API 620 covers pressurized tanks rated up to 15 PSIG, designed for lower temperatures and higher-pressure service.

2. Which standard applies to LNG storage tanks?

API 620. It’s built for cryogenic tanks that need to hold higher internal pressure at very low temperatures, down to -325°F.

3. Can API 650 tanks handle high-pressure storage?

Not really. API 650 tanks are rated up to 2.5 PSIG, which is meant for atmospheric or near-atmospheric service. Anything requiring higher pressure falls under API 620.

4. Is API 620 only used for large tanks?

Yes, API 620 applies only to tanks larger than 300 ft in diameter. API 650 has no such size restriction.

5. What’s the maximum temperature an API 650 tank can handle?

Up to 500°F. API 620 covers a much lower temperature range, down to -325°F, for cryogenic applications.