1. Different types of weld: flat welding seam can’t be detected by X-ray, but butt weld can. The welding seam form of flat welding flange with neck is fillet weld, while that of butt welding flange with neck is girth weld; flat welding is two fillet girth welds, and butt welding is one butt girth weld. The difference between the flat welding flange with neck and the flat welding flange without neck is that the flat welding flange with neck is more than the flat welding flange without neck, and the boss without flange is also flat fillet weld. The weld joint between the neck butt welding flange and the connecting pipe belongs to class B seam, while the weld joint between the neck flat welding flange and the connecting pipe belongs to class C seam, so the NDT after welding is different.
2. Different materials: the material of flat welding flange with neck is machined from ordinary steel plate with the thickness meeting the requirements, while the material of butt welding flange with neck is mostly made of forged steel parts.
3. The nominal pressure is different: the nominal pressure of the flat welding flange with neck is: and the nominal pressure of the neck butt welding flange is: 1 — 25MPa. Obviously, the pressure level of the flat welding flange with neck is lower.
4. Different connection modes: the structural difference between the welded neck flange and the neck butt welding flange lies in the difference in the connection mode between the connecting pipe and the flange. Generally, the flat welding flange with neck is the fillet connection between the nozzle and the flange, while the butt welding flange with the neck is the butt joint between the flange and the nozzle.
