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

2. Divided by petrochemical (SH) industry standards: Threaded Flange (PT), Weld Neck Flange (WN), Flat Weld Flange (SO), Socket Weld Flange (SW), Lug Flange (LJ), Flange Cover (not specified).

3. Divided by mechanical (JB) industry standards: Welding Neck Flanges, Blind Flanges, Plate Flange, Welding Ring Plate Flange, Sliding Plate Flange, Bevel Ring Plate Flange, and Flange Cover.

4. Categorized by national standards (GB): Whole Flange, Threaded Flange, Weld Neck Flange, Blind Flange, Socket Welding Flange, Ring Type Joint Flange with Weld Neck, Plate Flange with Weld Neck, Ring Flange Plate Type Loose Fit Flange, Plate Flange with Weld Neck Loose Fit, Beveled Ring Plate Type Loose Fit Flange, Flange Cover.