What is the Advantage and Disadvantage of What is a Reducer Socket

As we know there are four connecting types for the pipe fittings: Socket weld, butt weld, threaded, and flanged.

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In terms of steel pipe fittings for pipeline projects, socket weld fittings and butt weld fittings are two popular options.

However, since each type has its own advantages and disadvantages, you might be unsure about which one is best suited for your specific purpose. To help you make an informed decision, we have prepared a comparison between socket weld and butt weld fittings. Read on to learn more.

What is Socket Weld Pipe Fittings

A socket weld fitting is a type of pipe attachment detail where the pipe is inserted into a recessed area of a fitting, valve, or flange. To join the pipes or valves to other sections of the pipe, fillet-type seal welds are applied. Socket weld fittings are a good choice in certain cases due to their advantages of strong structural strength and high leakage integrity. These factors are important considerations when designing a pipeline project.

As below picture you can see the shape of 90 degree of socket weld elbow:

How to describe socket weld pipe fittings dimensions correctly

When placing a request for socket weld fittings, it is important to specify the OD (outside diameter) dimensions and the pressure requirements (or thickness schedule). Socket weld fittings have pressure ratings that are typically expressed in class , class , and class .

Socket weld pipe fittings are usually simplified as SW pipe fittings, so you will see some descriptions like SW elbow, SW tees, SW couplings etc.

Usage about socket weld fittings

Due to their high-pressure capabilities, socket weld fittings are commonly used in a wide range of industrial processes.

• Socket weld pipe fittings, such as elbows, tees, and reducers, can be used in pipelines to convey toxic, flammable, or expensive materials where leakage is not acceptable.
• Used in conjunction with ASME pipes to facilitate changes in dimensions.
• Applied in situations where the pipe work is considered to be permanent. They are designed in a way that provides good flow characteristics.
• Manufactured in accordance with ASTM A234 standards and can also confirm to ASME B16.11. This is a standard that covers dimensions, pressure-temperature ratings, marking, tolerances, and requirements for materials for carbon steel and forged carbon. In terms of acceptable material forms, they include bars, forgings, seamless tubes, and seamless pipes which conform to the requirements of fittings chemicals, mechanical property, and practices.

Socket weld pipe fittings types

Similar to butt weld fittings, socket weld fittings are available in various material types, including stainless steel, carbon steel, and alloy steel. These fittings are used in a wide range of applications and include socket weld elbows, socket weld tees, reducing tees, reducers, couplings, and socket weld flanges, among others.

Unit Weight in KG for SW fittings – Comply with ASME B16.11

Socket weld Couplings

• Full-coupling
This pipe can join two pipes or to a nipple.

• Half-coupling
This can be directly welded to the run pipe in order to make a branch connection.

• Reducing coupling
It helps to join two different outside diameters of a pipe.

• Reducer insert
These have been manufactured according to MSS SP-79. It helps to enable economic and quick combinations of pipeline reductions. As such, these can be made by using standard socket weld fittings.

Socket weld Union

A union is a type of screwed joint consisting of three interconnected pieces. It comprises two internal threads and a centerpiece that draws the ends together when rotated. Therefore, it is important to tightly screw the unions before welding the ends together. This helps minimize seat warping.

Socket weld Elbow

Socket weld elbows, also known as SW elbows, come in two types: 45 degrees and 90 degrees. They are manufactured through forging processes and are available in both long radius (LR) and short radius (SR) models. The LR model has a radius of 1.5 times the outer diameter (OD), while the SR model has a radius of 1 times the OD. Socket weld elbows are commonly used in pipelines to change the direction of fluid flow.

Socket weld Tee (SW Tee)

Tee Straight and Reducing Tee
A socket weld reducing tee is used to create a 90-degree branch from the main run of a pipe. It has a smaller diameter branch that connects to the smaller pipe branch.

Sockolet

A sockolet (a combination of “sock” and “olet”) is a type of socket weld pipe fitting that serves the same purpose as a weldolet or threadolet. It is used to weld a smaller diameter pipe into a larger diameter pipe body. However, what sets sockolets apart is the unique socket they have, which is located inside the olet. This socket provides a secure 90-degree turn and higher strength to handle high pressures. The bore of the sockolet is connected to the outlet bore, while the counter bore spans the outer diameter (OD) of the outlet to support the pipe seated on the socket, ensuring stable installation and welding strength. Like other socket pipe fittings, sockolets are available in pressure ranges of #, #, and #.

SW Cross

The Cross can also help to make a 90-degree branch from the main run of the pipe.

SW Cap

Cap is the end cap. It is used to seal the end of the pipe.

Socket Weld Flange – Another SW fittings

Socket weld flanges (SW flanges) are typically used for smaller pipes that have high pressure requirements. The flange has a specific shape that includes a recessed shoulder on the inner bore. This shoulder allows the pipe to be inserted correctly, after which welding is done to connect the pipes and flanges. This welding structure ensures a smooth bore and efficient transmission of liquids in the pipelines.

SW flanges includes RF (Raised Face), FF (Flat Face) or RTJ face (Ring Tenon Joint) type, pressure ratings classified in 150#, 300#, 600# and up to #.

Socket Weld Advantages and Disadvantages

Advantages

• The pipe needs to be beveled in preparation for welding.
• Temporary tack welding is generally not required for alignment because the principles in fitting ensure proper alignment.
• The socket weld metal is unable to penetrate the bore of the pipe.
• Construction costs have been found to be lower than those of butt-welded joints due to the elimination of special machines and the lack of exact fit-up requirements.

Disadvantages

• The welder should ensure that the expansion gap between the socket shoulder and the pipe is 1.6mm.
• The presence of internal crevices and expansion gaps in socket weld systems can promote corrosion. As a result, they are considered less suitable for radioactive or corrosive applications.
• These types of fittings are also not suitable for Ultra High Hydrostatic Pressure in food industries. This is because, in addition to not allowing full penetration, they also leave crevices and gaps that are difficult to clean.

Considering the above reasons, butt welding is better than socket welding on providing higher strength and higher pressure resistances.

Differences between socket weld and butt weld fittings

In the case of SW fittings, the standard reference is ASME B16.11. According to this standard, a pipe can be inserted into the recessed area of the fitting. Both the fitting and the pipe should be square cut and do not require any additional preparation or beveled ends, except for cleaning the outside surface. This simplifies the installation and welding processes.

For butt weld (BW) fittings, the standard reference is ASME B16.9. These fittings are welded onto the ends of the pipes, and their thickness is the same as that of the pipes. In this case, the ends of the fittings can be beveled.

Application differences between SW and BW fittings

Socket weld (SW) fittings typically have about half the strength of butt weld fittings. Therefore, SW fittings are primarily used for small pipelines with diameters of NPS 2 or even smaller.

On the other hand, butt weld fittings provide better strength and are suitable for high temperature or high pressure pipelines. They can also be used when a welded joint with strength equal to or greater than that of the base metal is required.

How to install – Socket weld vs Butt weld

In the case of SW fittings, they are relatively easy to install. A gap of approximately 1/6 inches at the bottom of the gap is required to allow access for the socket and accommodate thermal expansion. However, this gap can lead to over-stressing, causing cracks in the fillet weld of the fitting. Additionally, SW fittings have been found to be problematic in corrosive fluid services due to crevice corrosion. They are also prone to corrosion due to the discontinuity of smooth pipe internals.

On the other hand, butt weld fittings have been found to be superior in terms of fatigue resistance, strength, temperature compliance, and corrosion resistance. However, they can be more challenging to weld and properly fit-up. This requires more time and the expertise of skilled welders.

Socket weld and butt weld price differences

When considering the use of fittings for any construction project, price is a significant factor that needs to be taken into consideration.

When it comes to socket weld fittings, their price is generally higher compared to butt weld fittings of a similar size. However, the additional cost associated with butt weld fittings is higher for installation than SW fittings. This is due to the inclusion of skilled welders and other labor costs.

We hope that we have been able to assist you in gaining a better understanding of socket weld and butt weld fittings. If you have any inquiries regarding SW fittings, please feel free to contact us.

How Socket Welding Works

Socket welding is named for the fittings into which the pipes are placed for welding. These fittings include recessed sockets into which the pipes are inserted before being welded into place.

When inserting the pipe into the socket it is important to leave a gap between the end of the pipe and the bottom of the socket. This gap prevents a stress failure from occurring when the heat from the welding process causes the pipes to expand against the socket. This gap can be manually measured and marked with a reference line on the pipe, or a permanent fitment tool can be inserted into the fitting to ensure the pipe does not bottom out into the socket. Once placed in position, the pipe is fixed in place by fillet welding where the pipe diameter meets the socket.

Socket welds create sealed, leak-proof, high pressure pipeline configurations for the transporting of liquids or gases. Unlike butt welding, socket welds don’t require any pre-weld machining, although the pipe ends should be clean in order to assure the integrity of the weld.

Types

Socket weld fittings differ according to the pipe diameters and orientation they allow, meaning wide pipes can be joined to narrower ones and a pipe network can change direction or include branches. Socket weld fittings also include different coupling thread arrangements, as shown below:

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Full Coupling

This socket connects two pipes together, with threads at both ends to join the pipes. 

Half Coupling

Half couplings are similar to full couplings, but only have threads on one end. With half coupling, the non-threaded end is usually welded or fastened to piping using other means. 

Reducing Coupling

These fittings are used to join two pipes of different diameters, using different width sockets at either end.

Socket Weld Reducer Insert

This reducing fitting also allows for pipes of different diameters to be connected.

Socket Weld Union

Made up of two internal threads either side of an interconnected centrepiece, these three-part fittings use rotation to bring the pipe ends closer together. Because of this, the socket weld union must be screwed up tightly before welding the ends, which will minimise seat warping.

Socket Weld Elbow

Available at90 degree and 45-degree angles, these fittings allow pipe runs to change direction. SW elbows can be either short radius or long radius designs as required.

Socket Weld Tee

A socket weld tee fitting allows a T-junction to be inserted into a pipe network, creating a 90-degree branch off from a straight pipeline. A socket weld reducing tee can be used to create a same T-junction using a smaller diameter pipe as the branch.

Sockolet

Like the threadolet and the weldolet, the sockolet can be used to join a smaller diameter pipe with a larger one. The sockolet includes a socket in the olet (hence the name), which makes welding convenient. Able to create a 90 degree direction change, the sockolet is also able to withstand higher pressures.

Socket Weld Cross

This cross-formation fitting allows for two branches travelling in the same direction to make a 90 degree direction change.

Socket Weld Cap: A socket weld cap is used at the end of a pipe in order to seal it.

Socket Weld Flanges: SW flangeshave a recessed shoulder on the inner diameter which allows the pipe to be fitted correctly. These fittings are typically used for small diameter pipes and can work at higher pressures, offering excellent flow characteristics. There are a number of different SW flange designs, including flat and raised face versions, each with their own pressure ratings.

Advantages of Socket Weld Fittings

Socket weld fittings have a number of inherent advantages for joining pipes, including:

• The socket easily enables proper alignment, meaning that tack welds are not needed to align the pipes for welding
• Socket weld fittings have a lower risk of leakage than threaded fittings
• The socket design means that weld metal does not flow into the pipe bore
• Socket weld fittings are cheaper to install than butt weld fittings, as they do not require special machining due to the more relaxed dimensional requirements

Disadvantages of Socket Weld Fittings

Because the sockets do not allow complete penetration and must include an expansion gap between the socket shoulder and the pipe, socket weld fittings have areas where substances can build up that are difficult to clean.

These areas mean that socket weld fittings are unsuitable for use in the food industry for hygiene reasons and are also unsuitable for use with radioactive or corrosive substances that could build up and create maintenance or operating issues.

Uses and Applications

As seen above in the ‘disadvantages’ section, there are some applications that are not suitable for socket weld use, but the high pressure ratings associated with socket weld fittings mean that they are ideal for a wide range of other industrial applications.

SW pipe fittings can be used in pipelines to transport flammable, toxic or hazardous chemicals safely due to the lowered risk of leakage compared to other joining techniques.

Creating a leak-free permanent join, SW pipe fittings also allow for excellent flow characteristics. When manufactured to ASME and ASTM standard specifications, these fittings are shown to have met requirements for performance, including tolerances, pressure and temperature ratings, dimensions, materials and markings.

Socket weld pipe fittings are divided according to material type, such as alloy or carbon steel and stainless steel pipes. The different types of fitting lend themselves to different applications, whether couplings, reducers, reducing and regular socket weld tees, elbows, or flanges, with each available in different material types.

Socket Weld Inspection

Visual inspection is typically used to assess socket welds but other non-destructive testing methods can also be used.

Magnetic particle inspection can be used to locate surface and near surface defects in pipe welds, while radiographic inspection can also be used to locate internal voids.

FAQs

What is the Difference between Socket Welds and Butt Welds?

Socket weld and butt weld fittings are governed by different applicable standards (socket weld fittings are ASME B16.11 and butt weld fittings are ASME B16.9), as there are differences between the two types of weld.

Socket welds involve the insertion of the pipe into a recess at the joint and there is no need to bevel the pipe ends or prepare the materials other than to ensure they are clean.

Butt welds require the fittings to be the same thickness as the pipes so that they can be welded. Butt welded joints also need to be bevelled at the ends.

In addition to these practical differences, there are differences in performance, with butt weld fittings tending to be stronger. For this reason, socket weld fittings tend to be reserved for pipes with relatively small diameters. This difference in strength also means that butt welds are preferred for high temperature and pressure applications or where the weld joint strength does not have to be more than the base metal.

Is a Socket Weld a Fillet Weld?

A socket weld is generally considered to be different from a fillet weld, although there are some similarities between the shapes of the two welds.

How do you fit a Socket Weld?

To fit a socket weld, a pipe is inserted into the fitting’s recess, allowing a gap of at least 1/16” to allow for thermal expansion of the pipe under welding pressure. Once the pipe is in position, it can be welded in place with a series of fillet-type welds. The thermal expansion gap will prevent the weld from cracking should the pipe expand against the fitting.

What is a Socket Weld Flange?

Socket weld flanges tend to be used on smaller diameter, high pressure pipes. The pipes are inserted into the socket end and fillet style welds are applied around the top to hold it in place.

Can you X-Ray Socket Welds?

X-rays can be used to examine socket welds, using radiographic inspection techniques similar to those used in the medical industry.

Can you Radiograph Socket Welds?

Socket welds can be radiographed, although it is not an ideal method for determining the quality of the weld, it will tell you if there is an appropriate root gap.

When to use Socket Weld Fittings

Socket weld fittings are best used for small diameter pipes of NPS 2 or less. They can be used to join small bore pipe sections together using fillet weld type joins to seal the pipes to the fitting.

Why use Socket Weld Fittings?

Socket weld fittings join lines of small diameter pipe used to convey flammable, toxic or expensive materials that cannot be allowed to leak. Socket weld fittings can also be used for steam with a pressure of 300-600 psi. They can create a high strength union with a high flow characteristic and reduced chance of leakage.

Conclusion

Socket welding is used to connect pipes using a range of different fittings, allowing for changes in the direction and diameter of pipe networks as well as creating branches from existing pipelines.

The pipes are inserted into the socket weld fitting, which includes a recess to accept the pipe, making placement easy. Once inserted into the recess, allowing a gap at the bottom of the socket to prevent a potential stress failure, the pipe can be fixed in place with fillet welds around its outer diameter.

Mainly used for smaller sized pipes, socket weld fittings provide leak-proof joins that can withstand high pressures and deliver high-flow characteristics. The fittings are available in a range of styles and materials to suit a range of applications.

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