Orifice flange dimensions are covered in ASME B16.36. Orifice flanges are available from Class #300 to Class #2500. Class #300 flanges are available in threaded, slip-on and weld neck end types
In this article, I have tried to cover some of the special flanges such as Orifice flange, long weld neck flange, reducing and expanding flanges and flange olet that used in piping and equipment.Special flanges are not as common as regular flanges.
Orifice flanges are used instead of the standard pipe flanges when orifice plate or flow nozzle is used.
As already described before, the most used flange types acc. to ASME B16.5 are: Welding Neck flange, Slip On flange, Socket Weld flange, Lap Joint flange, Threaded flange and Blind flange.