What is the difference between butt welding flange and flat welding flange? AS2129 TABLE D FLANGE manufacturers tell you that butt welding flange is that the pipe diameter and wall thickness of the interface end is the same as the pipes to be welded, so they are welded like two pipes.

AS2129 TABLE D FLANGE manufacturers tell you that the flat welding flange is a concave table that is slightly larger than the outer diameter of the pipe at the interface, and the pipe is inserted and welded inside. Butt welding has better welding performance and less corrosion.
AS2129 TABLE D FLANGE manufacturers tell you that flat welding and butt welding are the welding methods for flange and pipe connection. When a flat welding flange is welded, only one side welding is required and there is no need to weld the inner port of the pipe and flange connection. Butt welding method Welding and installation of flanges requires double-sided welding of flanges.
The above information is the AS2129 TABLE D FLANGE manufacturer's introduction and analysis of the difference between butt welding flange and flat welding flange, hope it helps you.