How to Choose the Right Pipe Flange Standard: ASME vs. EN

When specifying pipe flanges for an industrial project, one of the most common questions engineers and procurement teams face is: which flange standard should I use? The answer depends on your project location, client requirements, and the piping system's pressure and temperature conditions. This guide breaks down the three most widely used international flange standards — ASME, EN (European), and JIS (Japanese) — to help you make the right call.

ASME Flanges (American Standard)

ASME B16.5 and B16.47 are the dominant standards in North America, the Middle East, and many parts of Asia-Pacific. ASME flanges are classified by pressure class (Class 150, 300, 600, 900, 1500, 2500) rather than by a fixed pressure rating, because the allowable pressure varies with temperature and material. This makes ASME flanges highly flexible across a wide range of operating conditions. If your project is destined for a U.S. or Gulf-region EPC contractor, ASME is almost certainly the required standard.

EN Flanges (European Standard)

EN 1092 flanges are specified across Europe and increasingly in Africa and parts of South America. Unlike ASME, EN flanges use a fixed Pressure Nominal (PN) rating — such as PN10, PN16, PN25, or PN40 — which indicates the maximum allowable pressure in bar at 20°C. EN flanges have different face types, bolt patterns, and dimensional requirements compared to ASME, meaning ASME and EN flanges are generally not interchangeable, even at similar pressure ratings. Always verify the complete flange specification including facing type (raised face, flat face, or tongue-and-groove) before ordering.

Which Standard Should You Specify?

As a general rule: follow the project's governing code. If a P&ID references ASME B31.3 process piping, use ASME flanges. If the project is under a European pressure equipment directive (PED), use EN. When in doubt, consult the project's piping material specification (PMS) document, which will define the flange standard, material, rating class, and facing type for each service.

At Fulihua Pipeline Equipment, we manufacture flanges to ASME, EN, JIS, KS, and GB standards, with the ability to provide mill test reports and third-party inspection documentation. Contact us at sales@flhmetal.com to discuss your project requirements.