The difference between valve flange, socket welding and butt welding

The difference between valve flange, socket welding and butt welding

1. Flat weld, butt weld and socket weld flanges

There are flat welding, butt welding and socket welding flanges for pipe flange welding

Socket welding generally inserts the pipe into the flange for welding. Butt welding uses a butt welding flange to butt weld the pipe and the butt joint. Higher butt welding flanges are recommended.

2. Several differences and applications

Generally, the requirements for butt welding are higher than those for socket welding, and the quality after welding is also good, but the detection methods are relatively strict. For butt welding, radiographic testing is required, and for socket welding, magnetic particle or penetrant testing is sufficient (for example, carbon steel is used for magnetic particle testing, and stainless steel is used for penetrating testing). If the fluid in the pipeline does not require high welding, it is recommended to use socket welding, which is convenient for detection

Most of the connection forms of socket welding are used in the welding of small diameter valves and pipes, pipe fittings and pipes. Small-diameter pipes generally have thinner walls, are prone to misalignment and ablation, and are more difficult to weld, so they are more suitable for socket welding. In addition, the socket of socket welding has the function of reinforcement, so it is often used under high pressure. However, socket welding also has disadvantages. One is that the stress condition after welding is not good, and it is easy to cause incomplete welding. There are gaps in the piping system, so the piping system used for crevice corrosion-sensitive media and the piping system with high cleanliness requirements are not suitable. Use socket welding. Furthermore, for ultra-high-pressure pipelines, even small-diameter pipelines have a large wall thickness, and socket welding can be avoided as much as possible for butt welding connections.

In short, socket welds form fillet welds while butt welds form butt welds. The butt joint is better than the socket joint from the analysis of the strength of the weld and the stress condition, so it is advisable to use the butt joint form in occasions with higher pressure levels and harsh service conditions. For details, refer to "HG20605".

3. Selection of flange

1. Choose the flange material that is really suitable for the material of the pipeline. For example, stainless steel pipelines are definitely not allowed to choose flanges such as carbon steel;

2. Select the right flange according to the nominal diameter (DN) of the pipeline and the nominal pressure (PN) of each section of the pipeline system. At present, the international pipe flange basically adopts the American standard system and the European standard system;

3. Select the flange structure and form according to the specific working conditions: such as flat welding with neck, loop flange, etc., the sealing surface forms include convex surface, full flat surface, concave-convex surface, etc.

4. For non-standard parts, design and manufacture shall be carried out according to the flange specification design procedure.