What are the technical requirements and standards for butt welding flanges

Butt welding flange is a kind of pipe fittings, which refers to the flange with neck and the transition of round pipe and butt welding with the pipe. Butt-welded flanges are not easy to deform, have good sealing, and are widely used. The following editor shares what are the technical requirements and standards for butt welding flanges

1. 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 PN of 1.6MPa-6.3MPa should 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.

　　 2. Butt welding flanges are generally made by forging or forging-rolling technology. When made of steel plate or section steel, the following requirements must be met:

　　 1. The butt-welded flange should be ultrasonically inspected without delamination defects;

　　2. It should be cut into strips along the rolling direction of the steel, then be bent and butt welded into a ring, and the surface of the steel should be formed into a cylindrical surface of the ring. The steel plate shall not be directly machined into a neck butt welding flange;

　　3, the butt weld of the ring should be a full penetration weld;

　　4. The butt weld of the ring shall be subjected to post-weld heat treatment and 100% radiographic or ultrasonic inspection, and the radiographic inspection meets the requirements of Class II of JB4730, and the ultrasonic inspection meets the requirements of Class I of JB4730.

　　 3. The outer slope of the neck of the butt-welded flange should not be greater than 7o. Welding 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.

In pipeline engineering, flanges are mainly used for pipeline connection. For pipelines that need to be connected, a variety of flanges are installed, low-pressure pipelines can use wire flanges, and welding flanges for pressures above 4 kg. Two-piece method Seal gaskets are added between the flanges and bolts are used to tighten them. Flanges with different pressures have different thicknesses and use different bolts. Water pumps and valves are connected to the pipeline. Parts of these equipment are also made into phases. The corresponding flange shape is also called flange connection. All connecting parts that are connected by bolts on the periphery of two planes and are closed at the same time are generally called "flanges", such as the connection of ventilation pipes. This type of part can be called It is a "flange type part". But this connection is only a part of the equipment, such as the connection between the flange and the water pump, it is not good to call the water pump "flange type parts". Smaller ones, such as valves, can be called "method Blue parts".

　　 Butt-welded flanges should be marked according to the nominal diameter, nominal pressure, sealing surface form code, the series code of the matched steel pipe (the code for the metric pipe is "series 2", and the imperial pipe is not marked) and the standard number.

　　 Marking example: convex face welded steel pipe flange with nominal diameter 80mm and nominal pressure 4.0MPa (25bar) (with metric pipe)

　　 flange DN80-PN40 M (series 2) GB/T9115.2-2000

　　 Nominal diameter 100mm, nominal pressure 5.0MPa (25bar) raised face neck flat welded steel pipe flange (with imperial pipe)

　　 flange DN100-PN50 RF GB/T9116.1-2000

　　Four, butt welding flanges are widely used

　　Flange is a disc-shaped part, which is the most common in pipeline engineering.Flanges are used in pairs.