What are SW and BW? Get It Perfectly

What is SW?

SW stands for Socket Welding on pipe ends. It is a welding procedure that joins stainless-steel pipes and fittings by valves or rest of the parts, and it is primarily used for stainless steel or carbon steel pipe that is less than 2 inches in diameter.

What is BW?

For pipe ends, BW stands for butt weld end. It refers to the welding of pipe ends to ends or pipes to pipe fittings. It uses resistance heat to weld two parts along the entire end face at the same time, which is now widely used in part welding.


What is the Difference Between SW and BW 

  1. a) Welding joint

Socket welding is the formation of a fillet weld and butt welding is butt welded. 

The strength and stress of butt welding is better than socket welding, so butt welding should be adopted when the pressure level is higher and the conditions of use are bad.

  1. b) Different diameter

Socket welding is most commonly used for tiny pipes with a diameter of less than or equal to DN100, such as small diameter valves and pipe fittings.

Butt-weld Fittings Malaysia is commonly used for welding pipelines larger than DN50, and it has a wide range of applications.

  1. c) Applied and CND

Socket welding is typically applied in small diameter but high pressure piping systems. Normally, socket weld is a magnetic particle test or a penetration test.

In addition, 100% non-destructive testing is required for butt welding to ensure no leakage, so its requirement is higher. 

  1. d) End to be welded

Socket welding is usually with a single end for pipes, it will fit into fittings or the connected end of the valve to the weld.

The connection for butt welding is frequently made with a 30°-37.5° bevel end, which makes filling and welding easier. The linked ends of thin pipe and fittings, such as EN 10253-4 / -3 and food-grade pipe fittings, are smooth and not bevelled.

Butt welding typically has more strict criteria than socket welding. Furthermore, the quality of butt welding has improved. As a result, the test criteria for butt welding are quite stringent. Post-welding radiography control is required for butt welding. Only a magnetic particle or penetration examination is necessary for socket welding (such as carbon steel for magnetic particles, stainless steel for penetration).

Butt-weld Fittings Malaysia

The advantage of socket welding over butt welding

Socket welds cannot be tested by x-ray test, but butt weld can do the test. Therefore, it is recommended to use butt welding for the high demands of welding joints. Usually, the normal requirements and quality of butt welding are more stringent than socket welding, but its detection methods are also relatively strict.

If the pipeline fluid requirements are not strict, socket welding is highly recommended, and its testing is more convenient. For socket welding, its connection is typically applied to valves, fittings and pipes of small diameter, since those with small diameter have a thin wall thickness, and they can be easy to pass through and ablation. If they are difficult to butt weld, they are more suitable for socket welding. In addition, the solder end can be used for reinforcing, so it can also be used in high pressure.

However, socket welding also has drawbacks. The first is that its stress condition is not good after welding, which will not easily make the weld fully penetrate and leave cracks in the pipe. Therefore, socket weld is not suitable for pipes related to sensitive fluids or high purity piping systems. Also, for small diameter pipes with high wall thickness, it is more recommended to use butt welding instead of socket welding if butt welding can be done.

In short, socket weld forms a fillet weld, while butt weld forms a butt weld. From weld joint strength, stress, and other analyses, butt welding performs better than socket welding. If it is necessary to weld in a high-pressure or severe environment, it is recommended to use the proper welding method.

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