What sealing surface is used for plate flat welding flange

Flat welding flanges are also called lap welding flanges. The connection between the flat welding flange and the pipe is to insert the pipe into the inner hole of the flange to the proper position, and then weld. Its advantage is that it is easier to align during welding and installation, and the price is cheap, so it has been widely used. Calculated according to internal pressure, the strength of the flat welded flange is about two-thirds of the corresponding butt welded flange, and the fatigue life is about one-third of that of the butt welded flange. Therefore, flat welding flanges are only suitable for piping systems with relatively low pressure levels and less severe pressure fluctuations and oscillations. Flat welding flanges can be subdivided into two types: neck flat welding and plate flat welding.

　　The basic shape of socket welding flange is the same as that of flat welding flange with neck. There is a bearing hole in the inner hole of the flange. The pipe is inserted into the bearing hole and welded, and a circle of welding seam is welded on the back of the flange. Because there is an open space between the flange and the pipe, corrosion sometimes occurs. If the inside is welded with a seam, this corrosion can be prevented. The fatigue strength of socket welded flanges welded on both sides of the front and back is 50% larger than that of flat welded flanges, while the static strength is the same. When using this flange, its inner diameter must be the same as the pipe inner diameter. Socket welding flanges are only suitable for pipes with nominal diameters below DN80.