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

2. Categorized 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: Full Face Flange, Weld Neck Flange, Plate Flange, Weld Neck Plate Flange, Flat Face Plate Flange, Beveled Edge Plate Flange, Flange Cover.

4. Classified by national (GB) standards: weld neck flange, threaded flange, slip-on flange, flat welding flange with neck, socket welding flange with neck, lap joint ring weld neck loose flange, plate flat welding flange, lap joint ring plate loose flange, flat ring plate loose flange, bevel ring plate loose flange, flange cover.