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Guide to DIN Flanges

In the United States, flange standards are set by the American Society of Mechanical Engineers (ASME), American National Standards Institute (ANSI), and American Water Works Association (AWWA) but a variety of international standards also apply to flanges outside the USA. Deutsches Institut für Normung (DIN) is one such system that complies with European and International standards.

About Deutsches Institut für Normung (DIN)

Deutsches Institut für Normung (DIN), or the German Institute for Standardization, is the official body that designates industrial and non-industrial standards for Germany. DIN is also the national standards body that determines the German edition of European and International Organization for Standardization (ISO) standards. Compatible parts and components are imperative to proper function and safety, and relying on a set of standards like DIN ensures consistency between manufacturers and suppliers.

What’s the Difference Between DIN, ASME, and ANSI Flanges

While America’s most common standards for flanges and fittings are AWWA, ANSI, and ASME, European and international industries rely on DIN standards, which use the metric system. DIN flanges are available in the same flange styles as ASME/ANSI flanges, such as slip-on, weld-neck, and blind flanges. Similar measurements are taken to determine the appropriate flange size—including outer and inner diameter, the number of bolt holes, and bolt hole and bolt circle diameter. However, for DIN flanges these dimensions and the pressure ratings are different than those on an AWWA, ANSI or ASME flange.  For this reason, DIN flanges should be paired with piping system components that comply with the same standard.

What Is a DIN Flange?

DIN sets industry standards for quality assurance and safety, including flange materials requirements and pressure and temperature rating. While DIN flanges are less common in the United States, imported systems and equipment or international maritime vessels may require these metric pipe flanges and parts. Because compatible piping system components are important for proper function, flange distributors like API International, Inc. often stock flanges manufactured to Deutsches Institut für Normung specifications.

Are DIN and ANSI Flanges Compatible?

DIN flanges are not interchangeable with ANSI- or ASME-rated flanges or piping systems because mismatched flanges cannot be mated. There is no exact DIN-to-ANSI flange conversion—even if the bolt holes align, there may be a disparity between pressure ratings or other aspects of the standards. While adapters can be custom machined to facilitate matching European standard and American standard piping components, using the appropriate DIN components is a quicker, easier option.

How to Choose DIN Flanges

Ordering DIN flanges requires the same steps as selecting ANSI or AWWA flanges: Determine the required materials, pressure requirements, and appropriate flange size. If your piping system requires metric flanges, the dimensions and pressure rating differ from non-DIN flanges.  Always refer to the standards for the intended application to ensure the flanges are manufactured to the correct dimensions and tolerances.

DIN Flange Measurements

DIN flange measurements use the metric system, including millimeters (rather than inches) for length and bar (instead of PSI) as the unit of pressure, as is the international standard. Required measurements for DIN flanges include the Inner Diameter (ID) and Outer Diameter (OD). Also consider the number of bolt holes necessary, as well as the measurement from the center of one bolt hole, directly across to the center of the adjacent bolt hole.

Then, refer to the corresponding measurement chart to determine the appropriate flange size based on the measurements. A DIN measurement chart may include a comparison of inches to millimeter measurements, but the physical measurement isn’t the only consideration when choosing the appropriate flange. Keep flange pressure rating requirements in mind, as well.

DIN and Pressure Rating

While DIN and ASME/ANSI flanges may be sized for proper bolthole alignment, be aware that the pressure-temperature rating and other standards are not equivalent. DIN standards use Pressure Nominale (PN) to designate a pressure rating—for example, PN16 is suitable for use up to 16 bar at ambient temperature.

ANSI standard lists “Class,” which is the pressure-temperature rating based on PSI, with different pressure ratings based on a maximum temperature. When ordering flanges, confirm compatibility based on flange measurements, bolthole alignment, and the pressure rating.

DIN Fittings and Accessories

DIN flanges match pipe ends that comply with the same standard, but accessories and fittings must also be the correct size. For a leakproof seal, ensure your gaskets are within the specified dimensional tolerances for use with DIN fittings.

When choosing piping system components, determine the appropriate flange based on application and piping system standards. Explore our Resource Center for more information regarding flanges and piping systems, or contact us with questions about flange types, measurements, or custom options.

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