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Commonly found in industrial settings, flanges are available in various shapes and sizes, and can be constructed from various types of material, such as steel, brass, or aluminum. The type of material that flanges are made from, however, does not have any bearing on flange sizes. Industrial standards are in place to ensure that mating flanges match, although different countries employ their own sets of standards. In the United States, for instance, the American Society of Mechanical Engineers (ASME) or American National Standards Institute (ANSI) regulate flange standards. When it comes to German flange manufacturing standards, on the other hand, the governing body is the German Institute of Standardization or Deutsches Institut für Normung (DIN).
Essentially, designation as a DIN flange means that a flange has been constructed in accordance with the guidelines of the German Institute of Standardization. In other words, the set of standards a manufacturer follows during the construction of a flange determines whether it is a DIN flange, an ASME flange, or an ANSI flange. For a particular project, it is important to maintain consistency in the type of flanges used, since a DIN flange may not exactly match an ASME or an ANSI flange.
Flange sizes often require more attention than the materials used in their construction, and these sizes are determined by the ASME, ANSI or DIN flange standards. The reason for this is that flanges belonging to a particular system are designed to exactly match other flanges of the same size in the same system. Two identical flanges that are or will inevitably be connected are known as mating flanges. Only when the sizes are a perfect match will mating flanges connect properly.
In the United States, the governing bodies that provide the guidelines used in flange construction, ASME and ANSI, provide a set of standards that all American flange manufacturers can follow. Likewise, the German Institute of Standardization provides this same service for its flange manufacturers. This ensures that any one brand of flange will match the same size from another maker, since replacing flanges often involves locating other flanges that will be exact matches, or mating flanges. Knowing which type of flange must be replaced — whether a DIN flange, an ASME flange, or an ANSI flange — can make finding the replacement significantly easier by ruling out the other types as options. In most cases, one style of flange will not replace another; for example, it is highly unlikely that an ASME flange could replace a DIN flange.