Socket Weld vs Butt Weld
Among the pipeline connection methods, socket welding and butt welding are two common connection methods, each with its own characteristics and suitable for different scenarios.
What is the Socket Weld?
Socket Weld is abbreviated as SW. For socket welding, it only requires inserting one pipe into the connecting end of another pipe, and the connection can be completed through welding. The overall connection point is solid and has a strong bearing capacity, providing a good guarantee for the operational safety of the pipeline. In addition, socket welding is also suitable for the connection of pipelines made of various materials and is applicable to various occasions.
What is the Butt Weld?
Butt Weld is abbreviated as BW. Butt welding, as a high-precision connection method, achieves a high-strength, aesthetically pleasing and stable connection by subjecting the ends of two pipes of the same diameter to heat treatment and then combining them after heating. Its weld seam is uniform and smooth, without protruding foreign objects, making the bearing capacity and leak-proof performance of the connection more superior. It is especially suitable for occasions with high requirements for aesthetics.
It is a common welding joint for high-pressure pipelines. High technical proficiency is required during welding. However, it has a tight connection and good leak-proof performance, making it suitable for high-pressure and high-temperature environments. It is mainly used in the connection of pipelines with relatively small diameters.
Main differences between socket weld and butt weld.
Connection method
- Socket Weld: After the pipeline is inserted into the socket, a fillet weld is made, and there is an assembly gap of 0.8-1.6mm.
- Butt Weld: The end faces of the pipelines are directly butted and welded. It is necessary to machine the bevel (such as V-shaped/U-shaped) to achieve full penetration.
Strength and applicability
- Socket Weld is only used for pipelines with a diameter less than or equal to DN50, and it is not suitable for working conditions with severe vibration or thermal cycling (stress concentration is likely to occur due to the gap).
- Butt weld has higher strength and is suitable for high-pressure/high-temperature working conditions (such as ASME B31.1 Class 1 pipelines).
Inspection and cost
- Socket Weld has a low installation cost. There is no need for bevel machining, and it is suitable for scenarios where space is limited.
- Butt weld requires 100% RT/UT inspection, while socket weld usually only undergoes surface inspection (PT/MT).
Standard basis
ASME B31.3 clearly distinguishes the applicable scopes of the two, and butt weld is the preferred option.
Summary of pros and cons of socket weld and butt weld.
Advantages of Socket Weld (SW)
- It requires fillet welding which is easy to achieve.。
- Especially suitable for small diameters working at relatively high pressures.
- No preparation required other than cleaning the surfaces.
- Suitable for different materials.
Disadvantages of Socket Weld (SW)
- Strength and stress resistance is reduced due to limited weld penetration in the fillet.
- Not suitable for systems with fluids sensitive to contamination or reaction with the welding.
Advantages of Butt Weld (BW)
- High strength and stress resistance which makes it suitable for high operation pressures.
- Suitable for large diameters and small diameters with high wall thickness.。
- Suitable for different materials.
Disadvantages of Butt Weld (BW)
- It requires a higher level of welding skills to be performed.
- It requires beveling the ends for proper weld penetration.
