Welding of flange

　　1. Flat welding flange: only the outer layer needs to be welded, and the inner layer does not need to be welded; It is generally used in medium and low pressure pipelines, and the nominal pressure of the pipeline shall be less than 0.25MPa. There are three types of sealing surfaces for flat welding flanges, namely lubrication

　　Type, concave convex type and tenon groove type, among which lubricating type is most widely used, and the price is affordable and cost-effective.

　　2. Butt welding flange: the inner and outer layers of the flange shall be welded. It is generally used in medium and high pressure pipelines. The nominal pressure of the pipeline is between 0.25 ~ 2.5MPa. The sealing surface of butt welding flange connection is concave convex,

　　The device is complex, so the labor cost, device method and auxiliary material cost are relatively high.

　　3. Socket welding flange: 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 flange: it is generally used in pipes with low pressure but corrosive medium, so this kind of flange has strong corrosion resistance, and the raw materials are mainly stainless steel.

　　This connection is mainly used for the connection of cast iron pipe, rubber lined pipe, non-ferrous metal pipe and flange valve. Flange connection is also used for the connection between process equipment and flange.