1. Divided by the chemical industry (HG) standards: Welding Neck Flange (WN), Threaded Flange (Th), Plate Flanged Socket Welding Flange (PL), Blind Flange (BL), Socket Welding Flange (SW), Flanged Socket Welding Flange (PJ/SE), Flat Socket Welding Flange (PJ/RJ), Lined Flange Cover (BL(S)), Flange Cover (BL) [2].

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

3. Divided by mechanical (JB) industry standards: Weld Neck Flanges, Blind Flanges, Plate Flanged Welding Flanges, Weld Ring Plate Flanged Lugless Flanges, Flanged Lugless Flanges, Bevelled Ring Plate Flanged Lugless Flanges, Flange Covers.

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