Differences in flat weld neck flange and butt weld neck flange

In terms of material, the necked flat weld flanges are processed with ordinary steel plates of the required thickness, while the necked butt weld flanges are mainly processed by forged steel parts.

The weld seam form is different, the weld seam between the pipe and the flange of the necked flat weld flange is in the form of fillet weld, while the weld seam between the necked butt weld flange and the pipe is in the form of ring weld. In addition, the weld seam of necked butt weld flanges can be detected by radiation, while the weld seam of necked flat weld flanges cannot be detected by radiation.

In terms of connection method, necked flat weld flanges are usually connected by flange angle, while necked butt weld flanges are butt connections between flanges and pipelines, which need to be welded on both sides.

In terms of nominal pressure, the nominal pressure of necked flat weld flanges is usually between 0.6~4.0 MPa, while the nominal pressure of necked butt weld flanges can be up to 1~25 MPa level.

In terms of non-destructive testing, due to the different materials and welding methods, the two types of flanges require different non-destructive testing after welding.

Picture: