1. Divided by chemical industry standards: 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), Ring Type Face Flange (PJ/RJ), Lined Flange Cover (BL(S)), Flange Cover (BL).

2. Categorized by petrochemical industry standards: Threaded Flange (PT), Weld Neck Flange (WN), Socket Weld Flange (SO), Blind Flange (not specified), Lug Flange (LJ), and Flange Cover (not specified).

3. By mechanical industry standards: full face flange, welding neck flange, flat welding plate flange, welding neck loose plate flange, flat welding loose plate flange, bevel edge loose plate flange, and flange cover.

4. By national standards: Weld Neck Flange, Threaded Flange, Socket Weld Flange, Slotted Flange, Blind Flange, Ring Type Joint Flange, Plate Flange, Ring Flange Plate Type Joint Flange, Flat Ring Plate Type Joint Flange, Flanged Ring Plate Type Joint Flange, Flange Cover.