1. Divided according to the chemical industry (HG) standard: Weld Neck Flange (WN), Threaded Flange (Th), Plate Flange (PL), Socket Weld Flange (SW), Flat Face Flange (SO), Blind Flange (BL(S)), Ring Type Joint Flange (PJ/SE), Lap Joint 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), Slotted Flange (SO), Socket Weld Flange (SW), Lug Flange (LJ), Flange Cover (not specified).

3. Divided by mechanical (JB) industry standards: full face flange, welding neck flange, flat welding plate flange, welding ring plate loose flange, flat ring plate loose flange, bevel ring plate loose flange, flange cover.

4. Categorized by national (GB) standards: Weld Neck Flanges, Threaded Flanges, Blind Flanges, Socket Weld Flanges, Lap Joint Flanges, Flanged Neck Socket Welding Flanges, Plate Flanges, Flanged Ring Plate Flanges, Slotted Ring Plate Flanges, Beveled Ring Plate Flanges, and Flange Covers.