What Is a Socket Weld?

Socket welding (socket weld) is a pipe-joining method in which a pipe is inserted
into a recessed area (the “socket”) of a fitting, valve, or flange, and then a
fillet weld is applied around the outside where the pipe meets the fitting.

How It Works

1. The pipe end is cut and prepared.
2. The pipe is inserted into the socket of the fitting.
3. A small gap (typically about 1/16 inch or 1.6 mm) is left between the pipe end
   and the shoulder inside the socket to allow for thermal expansion during welding.
4. A fillet weld is made around the circumference of the joint.
5. The weld is inspected according to the applicable code or specification.

Typical Applications

Socket welds are commonly used for:

• Small-diameter piping systems (typically 2 inches NPS and smaller)
• High-pressure service
• Steam systems
• Hydraulic systems
• Process piping in chemical and power plants

Common socket-weld fittings include:

• Elbows
• Tees
• Couplings
• Reducers
• Socket-weld flanges

Advantages

• Easier alignment than butt welding for small pipes.
• No need for precise end preparation or beveling.
• Strong, reliable joints for high-pressure applications.
• Faster assembly for small-bore piping.

Disadvantages

• The internal recess can create a crevice where corrosion may occur.
• Not generally preferred for services requiring complete internal cleanliness.
• Less suitable for large-diameter piping.
• Inspection of the weld root is not possible because it is hidden inside the socket.

Socket Weld vs. Butt Weld

Summary

A socket weld produces a strong connection with relatively simple fabrication,
while a butt weld generally provides a smoother internal flow path and is
preferred for larger piping systems.