What Are API Flanges?

API stands for the American Petroleum Institute, the organization that was formed in the 1930s to differentiate themselves from the ASA flanges at the time because they couldn’t handle the greater PSI that the API flanges required. ASA eventually became the standard for the American Society of Mechanical Engineers (ASME)/and American National Standards Institute (ANSI). Although both the API and ANSI/ASME flanges have the same origin, the API flanges differentiated themselves from the others.

Differences Between API and ANSI Flanges

The biggest difference between ANSI/ASME flanges and API flanges is that the API flanges are designed to handle a higher-rated operating pressure. They are constructed with higher strength and specifically designed to handle the high pressure seen in heavy oil refinery systems, bitumen upgraders, for nuclear power applications, and other petrochemicals and acids. API flanges are manufactured to resist corrosion, pitting, and cracking due to the stress of caustic solutions they are exposed to. This makes API flanges the only choice for refineries that handle substances such as oil and explosive gases, which require high pressure and temperature tolerances.

ASME/ANSI flanges provide its rating based on the pressure of a particular class of flange by the construction material and design temperature. This means that ASME/ANSI flanges are commonly used for handling water, steam, air, and gas for industrial processes.

Similarities Between API and ANSI Flanges

Although API and ASME flanges of similar dimensions may use the same circle and bolt holes. For example, the ASME/ANSI B16.5 flanges and the API 6A flanges use the same dimensions for weld neck, blind, and threaded flanges, they don’t use the same pressure rating system.

Bottom line: Don’t assume because the flange’s circle and bolt holes line up that they are compatible. Even though both the API and ASME/ANSI flanges are used for industrial processes, they are not the same.

Forged Components is the Premier Manufacturer of API Flanges

We are one of the world’s leading manufacturers of API flanges primarily for the oil & gas, and petrochemical industries. For more information, please call us at (281) 441-4088 or contact us online to get in touch with one of our sales specialists today.