1. Divided by the chemical industry (HG) standards: Weld Neck Flange (WN), Threaded Flange (Th), Plate Flange (PL), Socket Weld Flange (SW), Blind Flange (BL), Ring Type Joint Flange (PJ/SE), Flanged Lapped Joint Flange (PJ/RJ), Lined Blind Flange (BL(S)), and Blind Flange (BL) [2].

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

3. Divided according to the JB mechanical industry standard: overall flange, butt welding flange, flat welding plate flange, butt ring plate loose flange, flat ring plate loose flange, beveled ring plate loose flange, and flange cover.

4. Classified by national (GB) standards: flanged joints, threaded flanges,焊接 neck flanges, socket welding neck flanges, blind flanges, ring-type loose flanged neck flanges, plate-type welding neck flanges, ring-type loose plate flanges, flat welding ring loose plate flanges, bevelled ring loose plate flanges, and flange covers.