Socket Weld Fittings Types and Applications - Octal Steel

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.

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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.

Pipe fittings come in many forms with the most common being threaded fittings, socket weld fittings and buttweld fittings. This blog will explore the advantages of all three types, but especially the advantages of buttweld fittings and their applications.

Pipe fittings are essential parts of pipelines as they allow for the following:

• – A change in direction for the liquid flowing through the pipes
• – Branching of the pipe to allow the liquid to flow in two separate directions
• – A reduction in pipe diameter
• – The attachment of auxiliary equipment
• – The end of the pipeline

All the buttweld fittings supplied by Special Piping Materials are designed in accordance to ASME standards. They can be sourced from specialised manufacturers in many different materials including Super Duplex, Nickel Alloy, Stainless Steel, Duplex or even 6% Moly.

Threaded Fittings

Threaded fittings are mainly used for small pipe diameters and are probably the oldest method of joining piping systems. It is most commonly used in low-cost and non-critical applications. For example, threaded joints are often found in domestic water systems or industrial cooling water systems. They are less commonly used in high pressure and highly corrosive environments due to their vulnerability to fatigue damage and corrosion.

Threaded fittings are best for low-pressure and low-temperature installations where there is little chance of vibrations that could damage the integrity of the fitting.

The dimensional standards for threaded (screwed) fittings in Class , and are given in ASME B1.20.1.

Socket Weld Fittings

Socket weld fittings are when the pipe is inserted into a recessed area of a flange, fitting or valve. They are generally used in scenarios when the pipe dimensions are smaller, but the pipe work is permanent. They are used in various industrial processes such as the transportation of flammable, toxic or expensive material where no leakage can be permitted

Socket weld fittings Class , and are manufactured in accordance with ASME B16.11. They have several advantages:

• – Construction costs are relatively low
• – The pipe ends do not need to be bevelled. This is because both the pipe and the fitting are square cut. This allows easy welding and installation.
• – The reduce the risk of leakage in comparison to threaded fittings
• – The metal used to weld the fitting will not be able to penetrate into the bore of the pipe.
• – The fitting itself ensures proper alignment so temporary tack welding is not required.

Due to the nature of the fitting, socket weld fittings do have certain disadvantages. The main disadvantage is that the potential gaps and internal crevices can leave the fitting vulnerable to corrosion or build-ups. This can cause operating or maintenance issues.

Buttweld fitting

Manufacturing:

A buttweld fitting is manufactured by the process of hot or cold forming, which means that it is bended and moulded to the correct shape. They are also heat treated to remove residual stresses and to achieve specific mechanical properties.

The ends of buttweld fittings have to be bevelled and the exact shape of the bevel depends upon the wall thickness of the pipe it is being attached to. The material of a buttweld fitting can be any one of a number of exotic materials such as super duplex, nickel alloy or 6% Moly. The majority of the time, the material of the fitting is the same as the pipe system that it is welded to.

Buttweld fittings are defined in the ASME B16.9 standards, with light-weight corrosion resistant fittings made to MSS SP43 specifications.

These valuable fittings are available in many different shapes, dependent on the intended purpose:

• – ‘Elbows’ are used to alter the pathway of a pipeline
• – ‘Reducers’ are needed to reduce or increase the size of the pipe bore size
• – ‘Tees’ or ‘Crosses’ are used to split the flow in the pipe multiple ways
• – ‘Caps’ are used if the pipeline needs to be closed off

Applications:

Buttweld fittings can be used in a wide variety of industries to alter, divide or end the flow of fluids. These operations include the following: waste treatment facilities, chemical processing, breweries, petrochemical facilities, cryogenic plants, paper production, gas processing and even nuclear power plants. The wide range of applications demonstrates the robustness of a buttweld fitting and how much this particular type of fitting is relied upon.

Advantages:

Buttweld fittings can withstand pressures and temperatures in very harsh environments. They are generally considered to be the most robust welding fixture, no matter what industry it is required for. However, they do take a considerable time to fit and a highly skilled installer is required to weld them correctly on site.

• – Welded connection offers a more robust, a stronger and a more leak-proof piping connections.
• – The nature of the continuous metal structure provides added strength to the overall piping system.
• – The smooth inner surface and gradual directional changes provide a seamless flow, thus minimising pressure drops and turbulence inside the pipe.
• – Provide the option of various different turn radiuses due to the manufacture of Short Radius fittings, Long Radius fittings and 3R Elbows.
• – They are cost effective compared to the counterpart fittings in the threaded or socket weld varieties.
• – They have a long service life and are cost effective to purchase and deploy.
• – Buttweld fittings can withstand corrosion and erosion more effectively than its socket weld and threaded equivalents.
• – A welded system uses comparatively less space that the other alternatives.

Special Piping Materials supply of Buttweld Fittings

Here at Special Piping Materials, we have worked with specialist mills and manufacturers for many years to source a wide range of high quality and reliable buttweld fittings. We have a variety of different fixtures available in different sizes and materials.

All our products are fully tested to international standards so you can be safe in the knowledge that you are buying high quality products. Speak to our sales team today in one of our offices across the globe.

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