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

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

3. Divided by JB mechanical industry standards: Full face flange, Weld neck flange, Plate flat welding flange, Weld neck ring type loose flange, Flat welding ring type loose flange, Beveled ring type loose flange, Flange cover.

4. Divided by national (GB) standards: Weld Neck Flange, Threaded Flange, Socket Weld Flange, Slab Weld Neck Flange, Slab Socket Weld Flange, Ring Type Joint Flange with Weld Neck and Loose Shell, Plate Type Slab Weld Flange, Ring Type Joint Plate Flange with Loose Shell, Plate Type Ring Flange with Loose Shell, Beveled Ring Plate Flange, Flange Cover.