1. Divided according to the chemical industry (HG) standards: Overall Flanges (IF), Threaded Flanges (Th), Plate Flange Welding (PL), Weld Neck Flanges (WN), Socket Weld Flanges (SO), Lap Joint Flanges (SW), Flanged Ring Expansion Joints (PJ/SE), Plain Weld Ring Expansion Joints (PJ/RJ), Lined Flange Covers (BL(S)), and Flange Covers (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. Categorized by mechanical (JB) industry standards: Full Flange, Weld Neck Flange, Plate Flange, Weld Neck Ring Flange, Flat Ring Flange, Bevel Ring Flange, and Flange Cover.

4. Divided by national (GB) standards: Flanged joints, Threaded flanges, Weld neck flanges, Socket welding flanges, Blind flanges, Weld neck loose flanged joints, Plate welding loose flanged joints, Ring welding loose flanged joints, Flat welding loose flanged joints, Bevelled ring loose flanged joints, Flange covers.