Large-diameter flanges, also called large flanges or large-bore flanges, usually refer toDN600 (24") and aboveflanges. In conventional flange standards, sizes below DN600 are classified as general-purpose standard specifications, while sizes above DN600 fall into the category of large-diameter flanges.

Large-diameter flanges are commonly found in the following standards:

  1. JB/T81-94 Plate-Type Slip-On Flange Standard: covers DN700 to DN3000 specifications;
  2. American Standard B16.47 Large-Diameter Welding Neck Flange Standard: covers 26" to 60" specifications, including flange covers;
  3. British Standard BS3293 Welding Neck Flange Standard: covers 26" to 48" specifications, including American Standard slip-on flanges;
  4. American Water Works Association Steel Water Supply Flange AWWA C207: covers 26" to 144" specifications.

Some of the above large-diameter flange standards are specific to particular industries. Commonly used standards in domestic engineering mainly include: HG20592~20635-2009 Ministry of Chemical Industry standards, JB/T4701~4703 pressure vessel flange standards, as well as wind power-specific flanges; internationally, B16.47 large-diameter butt welding flanges are more widely used.