1. Divided according to the chemical industry (HG) standard: Weld Neck Flange (WN), Threaded Flange (Th), Plate Flange with Lap Joint (PL), Socket Welding Flange (SO), Blind Flange (BL), Ferrule Type Flange (PJ/SE), Flanged Ferrule Type Flange (PJ/RJ), Lined Blind Flange (BL(S)), Lined Ferrule Type Flange (BL) [2].

2. Divided according to the petrochemical (SH) industry standards: Threaded Flanges (PT), Weld Neck Flanges (WN), Sliding Flange (SO), Socket Weld Flange (SW), Lug Flange (LJ), and Flange Cover (not specified).

3. Divided by mechanical (JB) industry standards: Full Flange, Weld Neck Flange, Plate Type Welding Flange, Weld Neck Plate Type Loose Flange, Flat Neck Plate Type Loose Flange, Bevelled Edge Plate Type Loose Flange, Flange Cover.

4. Categorized by country (GB) standards: Weld Neck Flange, Threaded Flange, Socket Weld Flange, Sliding Flange, Flanged Socket Welding Flange, Flanged Ring Weld Neck Loose Flange, Plate Flange, Flanged Ring Plate Loose Flange, Plate Flange with Welded Ring, Flanged Ring Plate Loose Flange, Flange Cover.