1. Divided by chemical industry (HG) standards: Welding Neck Flange (WN), Threaded Flange (Th), Plate Flange (PL), Flat Face Flange (FF), Socket Welding Flange (SW), Blind Flange (BL), Ring Type Joint Flange (RTJ), Lap Joint Flange (LJ), Lined Flange Cover (BL(S)), and Flange Cover (BL) [2].

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

3. Divided by mechanical (JB) industry standards: Full Flange, Weld Neck Flange, Plate Flange, Weld Neck Ring Flange, Flat Ring Flange, Bevel Ring Flange, Flange Cover.

4. Divided by national (GB) standards: Weld Neck Flange, Threaded Flange, Blind Flange, Socket Weld Flange, Lap Joint Flange, Ring Type Joint Flange with Weld Neck, Plate Flange with Socket Weld, Plate Flange with Weld Ring, Plate Flange with Flat Ring, Beveled Ring Plate Flange, Flange Cover.