Guide to DIN Flanges

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

About Deutsches Institut für Normung (DIN)

The Deutsches Institut für Normung (DIN), or German Institute for Standardization, is Germany's official body for defining industrial and non-industrial standards. DIN is also the national standards organization responsible for determining the German edition of European and International Organization for Standardization (ISO) standards. Compatible parts and components are critical to proper function and safety, and relying on a set of standards such as DIN ensures consistency among manufacturers and suppliers.

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

While AWWA, ANSI, and ASME are the most commonly used standards in the United States, European and international industries rely on DIN standards, which use the metric system. DIN flanges come in the same flange styles as ASME/ANSI flanges, including slip-on, weld-neck, and blind flanges. To determine the appropriate flange size, similar measurements are taken, including outer and inner diameter, the number of bolt holes, and bolt hole and bolt circle diameter. However, the dimensions and pressure ratings for DIN flanges differ from those for AWWA, ANSI, or ASME flanges. As a result, DIN flanges should be used in conjunction with piping system components that adhere to the same standard.

What Is a DIN Flange?

DIN establishes industry standards for quality assurance and safety, such as flange material specifications and pressure and temperature ratings. While DIN flanges are less common in the United States, these metric pipe flanges and parts may be required by imported systems and equipment or international maritime vessels. Because compatible piping system components are critical for proper operation, API International, Inc. and other flange distributors frequently stock flanges manufactured to Deutsches Institut für Normung specifications.

Are DIN and ANSI Flanges Compatible?

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

How to Choose DIN Flanges

Ordering DIN flanges is the same as ordering ANSI or AWWA flanges: Determine the necessary materials, pressure requirements, and flange size. Metric flanges have different dimensions and pressure ratings than non-DIN flanges if your piping system requires them. To ensure that the flanges are manufactured to the correct dimensions and tolerances, always refer to the standards for the intended application.

DIN Flange Measurements

DIN flange measurements follow the metric system, with millimeters (rather than inches) for length and bar (rather than PSI) for pressure, as is the international standard. Inner Diameter (ID) and Outer Diameter (OD) measurements are required for DIN flanges (OD). Consider the number of bolt holes required, as well as the distance from the center of one bolt hole to the center of the adjacent bolt hole. Then, using the measurements, refer to the corresponding measurement chart to determine the appropriate flange size. A DIN measurement chart may include a comparison of inches to millimeters, but physical measurement isn't the only factor to consider when selecting the right flange. Consider the flange pressure rating requirements as well.

DIN and Pressure Rating

While DIN and ASME/ANSI flanges can be sized for proper bolthole alignment, the pressure-temperature rating and other standards are not the same. Pressure Nominale (PN) is a pressure rating used by DIN standards; for example, PN16 is suitable for use up to 16 bar at ambient temperature. The pressure-temperature rating based on PSI is listed in the ANSI standard, with different pressure ratings based on a maximum temperature. Confirm compatibility based on flange measurements, bolthole alignment, and pressure rating when ordering flanges.

DIN Fittings and Accessories

DIN flanges correspond to pipe ends that meet the same standard, but accessories and fittings must also be the correct size. Make sure your gaskets are within the specified dimensional tolerances for use with DIN fittings for a leakproof seal. Determine the appropriate flange based on application and piping system standards when selecting piping system components. Visit our Resource Center for more information on flanges and piping systems, or contact us if you have any questions about flange types, measurements, or custom options.