1. Different welding seam methods: The welding seam of flat welding cannot be radiographically inspected, but the welding seam of butt welding can. The welding seam method of necked flat welding flange pipe and flange is fillet weld, while the welding seam method of necked butt welding flange and pipe is girth weld; flat weld is two fillet girth welds, Butt weld is a butt girth weld. The difference between a flat-welded flange with a neck and a flat-welded flange without a neck is that a flat-welded flange with a neck has one more place in the pipeline welding position than a flat-welded flange without a neck. The flange is also a flat flange, and the boss without flange is also a flat fillet weld. The welded seam of the necked butt-welded flange and the receiving joint belongs to the class B seam, and the welded joint of the necked flat-welded flange and the receiving joint belongs to the class C seam, and the non-destructive testing after welding is different.
2. The nominal pressure is different: the nominal pressure of the necked flat welding flange is: 0.6---4.0MPa, and the nominal pressure of the necked butt welding flange is: 1--25MPa grade, obviously, the necked flat welding flange The adaptation pressure level is lower
3. Different connection methods: The biggest difference in structure between the necked flat welding flange and the necked butt welding flange is the difference in the connection method of the receiving and the flange. The necked flat welding flange is generally the receiving and the flange corner connection , And the neck butt welding flange is the flange and the receiving butt joint.
Neck flat welding flanges generally can only be connected to pipelines, but not directly connected to butt welding pipe fittings; butt welding flanges can generally be directly connected to all butt welding pipe fittings (including elbows, tees, reducers, etc.) , Of course, also includes pipes.
The rigidity of the necked butt welded flange is greater than that of the necked flat welded flange, and the butt weld is stronger than the flat welded, and it is not easy to leak.
The necked flat welding flange and the necked butt welding flange cannot be replaced at will. From the viewpoint of production, the necked flat welding flange (SO is the abbreviation of SLIP ON) has a large internal diameter, which means a small weight and a low cost. Other nominal names Neck butt welding flanges (WN is the abbreviation of WELDING NECK) with a diameter greater than 250mm need to be tested, and SO flanges do not need to be tested, so the cost is relatively low.
Neck flat welding is used more on imported petroleum installations, similar to the S0 of the American standard, neck butt welding flange is used for highly damaging media