1. Divided by the chemical industry (HG) standard: Welding Neck Flange (WN), Threaded Flange (Th), Plate Flange (PL), Flat Face Flange (FF), Socket Welding Flange (SW), Ring Type Joint Flange (RTJ), Blind Flange (BL(S)), Blind Flange (BL) [2].

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

3. Divided by mechanical (JB) industry standards: Full Flange, Weld Neck Flange, Plate Welding Flange, Weld Neck Plate Flange with Loose Assembly, Flat Weld Plate Flange with Loose Assembly, Bevelled Ring Plate Flange with Loose Assembly, Flange Cover.

4. Categorized by country (GB) standards: whole flange, threaded flange, weld neck flange, slip-on flange, socket weld flange, ring-type weld neck loose flange, flat plate weld neck flange, ring-type flat plate loose flange, flat ring plate loose flange, rolled ring plate loose flange, and flange cover.