Socket Weld Flange

Socket weld flange simplified as SW flange, it has a recessed area (like a shoulder) in the flange bore, this shoulder serves as a guide to set the depth of the pipe that inserted to the flange. Socket welding flange initially designed for high pressure small diameters piping system.

If you want to learn more, please visit our website MIDAS.

Available Material:

Standard:
Carbon steel ASTM A105, ASTM A350 LF1/2, ASTM A181
Alloy steel ASTM A182 F5, F9, F11, F22, F91
Stainless steel ASTM A182 F304/L, F316/L
Outer Diameters: 1/2 inch to 24 inch, up to #
Special made: 24'' to 60'', up to 900#
Wall Thickness: Schedule 40 to 160
Pressure Ratings: Class 150 to Class
Face Type: RF, RTJ

How to Use

Insert the pipe end into socket weld flange, until the pipe bottom touch the shoulder area, pull back 1.6mm (1/16'') distance of the inserted pipe then do fillet welding. The point is to create a expansion gap (1 fillet weld) between the flange and the pipes or fittings.

How is Socket Welding Flange Generated

The socket welding flange was firstly to use for stainless steel superheater, due to avoid cracking defects caused by thermal stresses in heating processes, and after years development it became a standard applications for all types of material.

Socket Welded Flange Face Types

Socket welded flange inlcuding RF type and RTJ type, which like other types of welding flanges (slip on, weld neck or blind flange).

RF Type

RF socket weld flange has a small portion surrounding the flange bore that protrudes from the face. Gasket seat will be placed in this raised area.

RTJ Type

On the raised face surface there has a groove is RTJ type, which you can place a gasket ring to get better sealing performances.

​

Advantages

• Socket weld flange could replace threaded flange, to minimize the risky of leakage.
• No need to beveling before welding.
• Welding work outside of the pipe, will not penetrate the pipe bore
• It is recommended for applications where internal welding operations are particularly difficult. This sock welded construction eliminates internal pockets while avoiding warpage of welding heat and damage to the flange face caused by weld spatter. It has the same internal pressure as the sliding on the flange, and has a better fatigue life.

Disadvantages:

• Socket welded flange requires higher skills for welder, which the welding need to make sure that the expanding gap between the pipe and shoulder is 1/16 inch.
• The expansion gap create the chances for the crack defects, especially for anti corrosive pipes as stainless steel pipes, so the cracks between the pipe and flange will cause the corrosive problems. So SW flange will not be compatible with corrosive or radioactive environment, as this solid buildup at the joint can cause operational and maintenance problems. So that's why people use but welding more often as the welding completely through the pipe from outside to inside, which makes the connects more strong and anti corrosive.

Socket Weld Flange vs Slip On Flange

Socket welded flange shape is similar to slip on flange, differently it has a shoulder at the inner bore.

Slip On Flange - No shoulder at inner bore.

Socket weld flange static strength is equal to slip on flange, but it's fatigue strength is 50% higher than the double welded slip on flange.

Contact Us Now for an Immediate Offer

Related Products

Slip On Flange

Weld Neck Flange

Blind Flange

Lap Joint Flange

Socket Weld Flange

Threaded Flange

What is a socket weld flange?

Socket weld flanges have a socket in which a pipe is inserted; the pipe is secured by one fillet weld located on the exterior of the flange hub. A significant disadvantage with this type of flange is that it is not considered a high-integrity joint because the weld is difficult to prove; thus socket weld flanges are only suitable for low to medium classes (≤ ASME 600). Due to their lower integrity and unsuitability for use at higher pressures, socket weld flanges almost always have flat or raised faces.  

Socket Weld Flange Cross Section

If you want to learn more, please visit our website Thread Flange.

Socket weld flanges are designed for small nominal pipe sizes (≤ 4 inches, ≤ 10cm) and are common for ½ to 2-inch pipe sizes (1.3 to 5cm pipe sizes). The mechanical strength of a socket weld flange is similar to that of a slip-on flange, but the slip-on flange may use two welds.

The ASME B31.3 standard states that an approximate gap of 1⁄16th of an inch (1.5mm) between the socket and pipe end is required; this gap allows for thermal expansion due to welding and reduces the likelihood that the weld will crack. In practice, this means that the pipe should be fully inserted into the flange, then retracted by the desired amount (1/16th of an inch, 1.5mm); this gap has been highlighted red on the above image.

Socket Weld Flange

The advantage of socket weld flanges is their simple design, they are well suited for small pipe size applications e.g. 2 inches (5cm) and below, and for non-critical applications e.g. non-hazardous systems; they are not suitable for highly erosive or corrosive systems.

Non-Destructive Testing (NDT) Techniques

Socket weld flanges have only one fillet weld and this can be subjected to radiography to prove the weld, although in practice it is impractical. Magnetic particle inspection (MPI) and dye penetrant inspection (DPI) can be used to prove the weld. 

ASME Standards

Socket weld flanges are not specified in ASME class rating as per the ASME B16.5 standard. The ASME B31.3 standard states that an approximate gap of 1⁄16th of an inch (1.5mm) between the socket and pipe end is required.

Are you enjoying this article so far? Then be sure to check out our Flange Fundamentals Video Course. The course has over five hours of video content, a 52 page colour illustrated handbook (this article is an extract from the handbook), a quiz, and you will receive a certificate of completion when you finish the course. Enjoy!

Flange Types, Faces, and Surfaces - Explained!

This video is part of our Piping Flange Fundamentals Video Course

Additional Resources

https://www.octalflange.com/socket-weld-flange

https://www.texasflange.com/socket-weld-flanges

https://www.haihaopiping.com/socket-weld-flangesocket-welding-neck-flange.html