1, According to the national standard flange classification: overall flange, threaded flange, butt welding flange, necked flat welding flange, necked socket welding flange, butt welding ring with neck loose set flange, plate type flat welding flange, butt welding ring plate loose set flange, flat welding ring plate loose set flange, flanged ring plate loose set flange, blind flanges.

2, According to the classification of chemical industry standard flange: integral flange (IF), threaded flange (Th), plate flat welding flange (PL), necked butt welding flange (WN), necked flat welding flange (SO), socket welding flange (SW), butt welding ring loose set flange (PJ/SE), flat welding ring loose set flange (PJ/RJ), lined flange cover (BL (S)), blind flanges (BL).

3, According to the classification of petrochemical industry standard flange: threaded flange (PT), butt welding flange (WN), flat welding flange (SO), socket welding flange (SW), loose flange (LJ), blind flanges.