Flanges are key components in pipe connections, and their construction can be divided into the following key sections:
1. Sealing Surface: This surface directly contacts the gasket to achieve a seal. Common types include flat face (FF), raised face (RF), and ring joint (RTJ). For example, flanges with a PN16 pressure rating typically use an RF face, and the sealing width must be ≥3mm (according to GB/T 9124).
2. Flange Neck: This portion is welded to the pipe. The neck of a weld neck flange (WN) typically has a 7° bevel to reduce stress concentration.
3. Bolt Holes: This is used to secure the flanges together. The number of holes is generally a multiple of 4 (e.g., 8 holes for a DN100 flange). The hole diameter must be 1-2mm larger than the bolt diameter to ensure installation tolerances.
4. Flange Plate: This is the pressure-bearing portion of the flange. Its thickness is determined by the pressure rating. For example, the plate thickness of a DN50 flange with a PN40 rating is approximately 22mm (according to ASME B16.5).