The American Petroleum Industry (API), which includes all segments of the oil and natural gas sector in the United States, establishes a series of standards for the design and construction of welded steel storage tanks. These give rise to various models, each suited to the needs of the specific products they are to contain. Among the most prominent of these is the API 620.

What is the API 620 and why is it so important?

The API 620 tank is made of carbon steel, stainless steel and nickel alloys where low temperature use is required. In addition, its design features a flat or slightly raised bottom and a single centred vertical axis, with a minimum thickness of 3/16 inches.

This model is used for products with low internal pressure and low temperatures, such as cryogenic tanks. Another of its main advantages is that it can store any type of liquid.

Due to the diverse range of tank sizes and shapes that can be built, API 620’s regulations cannot encompass all design and construction specifics. If there are no complete rules for a particular design, the expectation is for the Manufacturer, with the consent of the Purchaser’s authorized representative, to provide design and construction particulars that are equally secure to those mandated by the API 620. 

The difference between API 620 and API 650

API 650 and API 620 have important differences in terms of their size, configuration and the materials used to manufacture them. However, the most important distinction between the two models is that the API 620 can store contents at a slightly higher pressure and much lower temperature than the 650.

However, they share many common features that make many non-experts confuse them. For example, both tanks share storage purposes, they can be constructed with the same materials (only low temperature ones) and both need a non-destructive inspection but not a third party one.

Keep reading: How to Revolutionize Your Industrial Engineering Projects Through Cryogenic Technology

API vs ASME: a matter of construction codes

Having a good grasp of the API and ASME codes allows us to understand their differences and the importance of their application to specific equipment.

The American Society of Mechanical Engineers, which focuses on setting safety standards for mechanical equipment, developed the ASME code for boilers and pressure vessels used in a variety of industries.

On the other hand, the API specifications are the set of best practices established to promote safety in the oil and gas industries. Some of them have been incorporated into industrial heating equipment regulations as well.

Current API 620 standard

The latest edition of the API 620 standard applies to the design of low pressure storage tanks. Section Q of this standard specifies requirements for materials, design and fabrication of metal parts for refrigerated tank systems. This standard applies to tanks storing liquid gases at a temperature of -325ºF or above.

Other types of API tanks

An in-depth awareness of other API tank standards allows us to understand the importance of this code when designing isolation tanks.


It predetermines the dimensions of the tank and, therefore, its storage capacity. Thus, by creating specific sizes and requirements prior to manufacture, the need for further engineering processes is reduced, along with the final cost.

This standard covers a variety of specifications, such as materials, manufacturing processes, or the design itself. These specifications are designed to provide tanks of adequate safety to use in the storage of liquids commonly handled and stored by the production segment of the industry.

API 653

This standard is intended as a guide to the inspection, repair and decommissioning of API 650 or API 12C models. Its scope focuses on specific tank components: foundation, bottom, shell, structure, roof and connections up to the first flange face.

This accreditation is only valid for a three-year term and it is given by the American National Standards Institute (ANSI) meeting the rigorous requirements established by the International Organization for Standardization (ISO).


This specification was designed to create safe and economical tanks for the storage of crude oil and other petrochemical products. It covers materials, fabrication, design and testing requirements for a bunch of steel storage tanks in different standard capacities and sizes. Its applications are: crude oil, process water, water and drilling mud.

You may like: Why are flat bottom tanks perfect for storing cryogenic gases?

Ultimately, API standards are a safety reference for storage tanks. Knowing our way around API 620 characteristics helps us to understand why a given tank model is suitable for application in cryogenic tanks.

For this reason it is so important to have an expert provider like Cryospain. As part of our services, we will advise you on the type of tank that best suits your needs, complying with the highest market standards. Why not contact us throught our website or at

cryospain tank

Contact us

Privacy Policy

Thank you! We'll get back to you as soon as possible.