1. Divided by the chemical industry (HG) standards: Weld Neck Flange (WN), Threaded Flange (Th), Plate Flange (PL), Socket Weld Flange (SW), Blind Flange (BL), Flanged Cover (BL(S)), Ring Type Joint Flange (PJ/SE), Ring Type Face to Face Flange (PJ/RJ), Lined Flange Cover (BL(S)), Flange Cover (BL) [2].

2. Divided according to the petrochemical (SH) industry standards: threaded flange (PT), welding neck flange (WN), flat welding flange (SO), socket welding flange (SW), loose joint flange (LJ), and flange cover (not specified).

3. Divided by JB mechanical industry standards: Full-face Flanges, Weld Neck Flanges, Plate Flange Welding Flanges, Weld Neck Ring Flange Plate Loose Assembly Flanges, Flat Ring Flange Plate Loose Assembly Flanges, Beveled Ring Flange Plate Loose Assembly Flanges, Flange Covers.

4. Categorized by country (GB) standards: Flanged Joints, Threaded Flanges, Weld Neck Flanges, Blind Flanges, Socket Welding Flanges, Flanged Ring Weld Neck Flanges, Plate Flange Welding, Flanged Ring Plate Flange, Plate Flange Welding Ring, Flanged Ring Plate Flange with Bevel, and Flange Covers.