Brief analysis of butt welding flange

Butt welding flange is used for butt welding of flange and pipe. It has reasonable structure, high strength and rigidity, can withstand high temperature and pressure, repeated bending and temperature fluctuation, and has reliable sealing. The butt-welded flange with a nominal pressure of 0.25～2.5MPa adopts a concave-convex type sealing face and the outer slope of the neck of the welding flange should not be greater than 7o.

　　 Butt-welded flanges strictly control technical parameters during production and welding to ensure that they can give full play to their role and value in production and use. Butt-welded flanges are not easy to deform, have good sealing, and are widely used. They have corresponding rigidity and elasticity requirements and reasonable butt-welding thinning transitions. The distance between the welding port and the joint surface is large, and the joint surface is protected from welding temperature deformation. The horn-shaped body structure is suitable for pipelines with large fluctuations in pressure or temperature or high temperature, high pressure and low temperature pipelines. It is generally used for the connection of pipelines and valves with a PN greater than 2.5MPa; it is also used for transporting expensive, flammable and explosive On the pipeline of the medium.

The level of butt welding flange and its technical requirements should meet the corresponding requirements of JB4726-4728.

　　1. Carbon steel and austenitic stainless steel forgings with nominal pressure PN of 0.25MP-1.0MPa are allowed to use Class I forgings.

　　2. In addition to the following regulations, forgings with a nominal pressure of PN 1.6MPa-6.3MPa shall meet the requirements for forgings of Class II or above.

　　 3. Those who meet one of the following conditions shall meet the requirements of Ⅲ and forgings:

　　(1) Forgings for flanges with nominal pressure PN ≥ 10.0MPa;

　　(2) Chrome-molybdenum steel forgings with nominal pressure PN> 4.0MPa;

　　(3) Ferritic steel forgings with nominal pressure PN>1.6MPa and working temperature ≤-20°C.

　　 Stainless steel butt welding flange ball valve connection:

1. First of all, the stainless steel butt welding flange ball valve has a flange on the valve body. According to a certain standard, holes with a standard eye distance are drilled. The joint end of the pipeline is also welded with the same standard flange. The bolt makes the stainless steel ball valve. The flange is tightly connected with the pipe flange;

　　 2. The butt-welded flanges are sealed with gaskets according to the working conditions. The gasket is placed between the sealing surfaces of the two flanges. After tightening the nut, the specific pressure on the gasket surface reaches a certain value and deforms, and fills up the unevenness of the sealing surface to make the connection tight and leak-proof;

　　 3. Butt welding flange connection is a detachable connection. There are three types of flange sealing surface: flat sealing surface, suitable for occasions with low pressure and non-toxic media; concave-convex sealing surface, suitable for occasions with slightly higher pressure; tongue and groove sealing surface, suitable for flammable and explosive , Toxic media and high pressure occasions. The type change of the flange surface also requires the stainless steel ball valve body to have the characteristics of being able to bear the corresponding application conditions.