First of all, the welding method is different: the welding method of the necked flat welded flange is fillet weld, and the welding method between the necked butt welded flange and the pipe is the girth weld.
Different materials, the materials of the neck flat welding flange are processed with thick general steel plates as required, and the materials of the neck butt welding flange are mainly made of forged steel parts. Different pressure: the nominal pressure of the necked flat welding flange is 0.6≤4.0 MPa, and the nominal pressure of the necked butt welding flange is 1~25 MPa. The necked flat welding flange and the necked butt welding flange cannot be replaced at will According to the manufacturing viewpoint, SLIPON flanges are large, low cost, and light in weight.
How to distinguish between necked flat welding flange and necked butt welding flange? Different weld shapes: flat welds cannot be inspected by radiography, but butt welds are inspected by radiography. The welding method of the flange and the flange is fillet welding, and the welding method between the necked butt welded flange and the pipe fitting is the girth weld, the flat weld is the two-angle girth weld, and the butt weld is the butt weld girth weld.
The difference between a necked flat welding flange and a non-necked flat welding flange is that in the pipe welding part, the welding of the flange without the neck is 1 unit less than the flange with the neck. No flat neck. The welds of flat-necked flanges and nozzles are classified as Type C joints, while the welds of butt-welded flanges and nozzles without necks are classified as Type B joints. The non-destructive testing after welding is different.