Socket Weld Fitting

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Socket Weld Flange Drawing`Socket weld flange with pipeSocket weld pipe fittings, abbreviated as SWF, are a type of pipe fitting used in various industries, including plumbing, oil and gas, petrochemical, and more.  These fittings are designed for connecting pipes or tubes of the same nominal size, typically in small to medium sized pipelines.  The pipe is inserted into a recessed area of the fitting before it is welded.  In order to prevent damage to the pipe and fitting, the pipe is then backed out a minimum of 1/16” to allow for thermal expansion of the pipe during the welding procedure.  If this clearance is not made, the weld can crack due to the pipe expanding against the fitting.  Socket weld fittings are known for their strength, durability, and leak free connections. 

Here's a brief overview of socket weld pipe fittings

  • Socket Weld Design  -  Socket weld fittings have a socket (or female) end and a plain (or male) end.  The socket end is designed to accept the pipe, while the plain end is inserted into the socket of another fitting or pipe.  The connection is made by welding the pipe into the socket.
  • Connection Method  -  The connection is made by inserting the pipe into the socket and then applying heat to the joint.  Once the material reaches the proper welding temperature, it is allowed to cool and solidify, creating a strong and permanent connection.  Non metallic pipe almost exclusively uses sock weld fittings for their permanent connections.  This is because the socket gives ample surface area for the glue to bond the two pieces together.
  • Size  -  SW fittings are used for piping that has a nominal pipe size (NPS) of 3 inches and below.
  • Welding  -  Because a fillet weld is used instead of a butt weld, there is no possibility for weld metal to enter the bore of the pipe.   Because a fillet weld is used, it can only be inspected by using non radiographic methods, such as magnetic particle or liquid dye penetrant methods.
  • Types of Socket Weld Fittings  -  There are various types of socket weld pipe fittings available.  There are three different pressure classes available for socket welded, 3000, 6000 and 9000.  In general, Class 3000 is for use with Schedule 80 pipe, 6000 - Schedule 160 and 9000 – XXH.  The pressure classes are based on the cold working pressure limits of 3000, 6000 and 9000 psi.
  • Materials  -  Socket weld fittings are available in various materials, including stainless steel, carbon steel, alloy steel, brass, and more.  The choice of material depends on the application's requirements, such as the fluid being transported and the operating conditions.

Socket weld pipe fittings are commonly used in applications where a secure and leak free connection is essential, such as in industrial processes and systems handling high pressure fluids.  Proper welding and installation are crucial to ensure the integrity and performance of the system.

Socket Weld Fitting Datasheets


Forged Fittings Socket Class Types

Class designations correspond to the maximum cold working pressure of fittings in pounds force per square inch.

Pressure Class2000300060009000
Socket Fitting - 80/XH 160 XXH
Threaded Fitting 80/XH 160 XXH -


The following links are for datasheets for the socket fitting range sizes covered by ASME B16.11.  If you would like to browse the datasheets for pipe fittings, please visit our Fittings Datasheets page. 

Forged Fittings Socket Sizes

  • Dimension tolerances in accordance with ANSI/ASME B16.11 do not include laterals, reducers and unions.
  • Fittings with special dimensions, threads, or counterbores can be made by agreement between the manufacturer and purchaser.  If the fittings meet all of the requirements of this Standard, they can be considered in compliance, provided they are appropriately marked.





45 Elbow 1/8 - 4 1/8 - 2 1/2 - 2
90 Elbow 1/8 - 4 1/8 - 2 1/2 - 2
Cap, Round 1/8 - 4 1/8 - 2 1/2 - 2
Coupling, Full 1/8 - 4 1/8 - 2 1/2 - 2
Coupling, Half 1/8 - 4 1/8 - 2 1/2 - 2
Cross 1/8 - 4 1/8 - 2 1/2 - 2
Lateral 3/8 - 2 3/8 - 1 1/2 1/2 - 1 1/2
Reducer 1/8 - 4 1/2 - 4 1/2 - 2
Tee 1/8 - 4 1/2 - 4 1/2 - 2
Union 1/8 - 3 1/8 - 2 -


Socket Fitting Advantages and Disadvantages

  • One of the benefits of using these types of fittings is that the end of the pipe doesn't need to be beveled before welding.  That is, the pipe end is a plain end instead of a bevel end.  This means that it uses a single fillet weld as opposed to a butt weld.  This means that the pipe fitter can install and weld without having to have a special clamp or tack welding, which is the case with butt welded pipe.
  • Strong and durable connection.
  • Suitable for high pressure and high temperature applications.
  • Smooth flow path, minimizing pressure drop.
  • Compact design for space constrained areas.
  • Socket fittings are generally easier to install compared to threaded or welded fittings.  They can be connected quickly and securely without the need for specialized tools or extensive training.
  • Socket fittings are often more cost effective than welded fittings since they don't require welding equipment or highly skilled labor.  Additionally, they are typically less expensive than threaded fittings.
  • These fittings can be used with various types of piping materials, including PVC, CPVC, ABS, and sometimes even metal pipes, making them versatile for a wide range of applications.
  • Properly installed socket fittings can provide a tight and leak resistant connection, reducing the likelihood of leaks and minimizing maintenance requirements.
  • Socket fittings allow for some degree of movement or flexibility in the piping system, which can be advantageous in environments where there may be slight shifts or vibrations.
  • If repairs or modifications are needed, socket fittings can be easily disassembled and reassembled without causing damage to the pipes or fittings.
  • If the welder does not leave a gap between the pipe and the shoulder of the socket, there is a risk that the weld will fail either during the welding process or under high temperatures.
  • This gap can cause solids to accumulate which can cause corrosion issues.  If the piping is used for multiple process fluids, this accumulation may contaminate the additional process streams.
  • Welding can introduce heat and potential stress to the pipe material.
  • Socket fittings may have pressure limitations compared to welded fittings.  They may not be suitable for high pressure applications or systems where pressure fluctuations are significant.
  • While socket fittings can be used with various piping materials, compatibility issues may arise when connecting different types of materials.  It's essential to ensure that the fittings and pipes are compatible to avoid potential leaks or failures.
  • Socket fittings are available in a range of sizes, but larger diameters may be limited compared to other types of fittings.  In applications requiring very large pipes, socket fittings may not be feasible.
  • While socket fittings are relatively easy to install, proper installation techniques are necessary to ensure a secure and leak free connection.  Improper installation can lead to leaks, failures, or compromised system integrity.
  • Some socket fittings may have temperature limitations, especially in extreme hot or cold conditions.  It's essential to choose fittings rated for the specific temperature range of the application.
  • In certain applications where aesthetics are important, the appearance of socket fittings may not be as desirable as welded fittings, which offer a smoother and more seamless look.


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