1. Divided according to the chemical industry (HG) standard: whole flange (IF), threaded flange (Th), plate flat welding flange (PL),焊接 neck flange (WN),焊接 face flange (SO), socket welding flange (SW), welding ring loose flange (PJ/SE), flat ring loose flange (PJ/RJ), lined flange cover (BL(S)), flange cover (BL) [2].

2. Categorized by petrochemical (SH) 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. Divided by the JB mechanical industry standards: Full Flange, Weld Neck Flange, Plate Type Flat Weld Flange, Weld Neck Ring Type Spool Flange, Flat Neck Ring Type Spool Flange, Bevel Ring Type Spool Flange, Flange Cover.

4. Classified by national (GB) standards: full face flange, threaded flange, welding neck flange, slip-on flange, socket welding flange, welding ring welding neck loose flange, flat welding plate flange, welding ring plate loose flange, flat welding ring plate loose flange, beveled ring plate loose flange, and flange cover.