1. Divided according to the chemical industry (HG) standards: Welding Neck Flange (WN), Threaded Flange (Th), Plate Flange (PL), Socket Welding Flange (SW), Blind Flange (BL), Seamless Ring Flange (PJ/SE), Sliding Flange (PJ/RJ), Lined Flange Cover (BL(S)), and Flange Cover (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 listed).

3. Divided by mechanical (JB) industry standards: Flanged Joints, Weld Neck Flanges, Plate Flange, Weld Neck Plate Flange, Flat Face Plate Flange, Beveled Edge Plate Flange, Flange Cover.

4. Categorized by country (GB) standards: Flanged joints, Threaded flanges, Weld neck flanges, Slab焊接flanges, Socket welding flanges, Weld ring neck loose flanges, Plate焊接flanges, Weld ring plate loose flanges, Slab焊接ring plate loose flanges, Bevel ring plate loose flanges, Flange covers.