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Flat welding: only the outer layer is welded, not the inner layer; It is generally used in medium and low pressure pipelines, and the nominal pressure of the pipeline shall be lower than

2.5MPa。 There are three types of sealing surfaces of flat welding flange, namely smooth type, concave convex type and mortise groove type. The smooth type is the most widely used one among them, with affordable price and high cost performance.

2 Butt welding: the inner and outer layers of flanges shall be welded, generally used in medium and high pressure pipelines, and the nominal pressure of the pipeline is 0.25~2.5 MPaz

Between. The hollow cover of butt welding flange connection mode is concave convex, and the installation is relatively complicated, so the labor cost, installation method and auxiliary material cost are relatively high.

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