Flange connection

Flange connection methods can be generally divided into five types: flat welding, butt welding, socket welding, loose sleeve, thread.

The first four are elaborated below:

1. Flat welding: only the outer layer is welded, and the inner layer is not needed; generally used in medium and low pressure pipelines, the nominal pressure of the pipeline should be less than 0.25MPa. There are three sealing surfaces for flat welded flanges, which are smooth, concave and convex, and tongue and groove. Among them, the smooth type is the most widely used, and it is affordable and cost-effective.

2. Butt welding: the inner and outer layers of the flange are to be welded, generally used in medium and high pressure pipelines, the nominal pressure of the pipeline is between 0.25 ~ 2.5MPa. The sealing surface of the butt welding flange connection method is concave and convex, and the installation is more complicated, so the labor cost, installation method and auxiliary material cost are relatively high.

3. Socket welding: generally used in pipes with nominal pressure less than or equal to 10.0MPa and nominal diameter less than or equal to 40mm.

4. Loose sleeve: Generally used in pipelines with low pressure but with corrosive medium, so this type of flange has strong corrosion resistance and the material is mostly stainless steel.

This connection is mainly used for the connection of cast iron pipes, rubber lined pipes, non-ferrous metal pipes and flange valves. The connection of process equipment and flanges is also flanged.