What are flanges and What are the different types of flanges?

by Muskan Ahuja

Posted on July 12, 2021 at 01:00 PM

What are flanges and What are the different types of flanges?       >


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What are Flanges

A flange is a projecting ridge or rim used to improve strength or weight distribution. Flanges join valves, pumps, pipes, and other pieces of equipment to form a pipeline system. It also enables easy washing, examination, and modification. Flanges are joined by welding or screwing. Flanged couplings are made by bolting two Flanges together and sealing the junction with a gasket.

Flanges are utilized when a piping junction needs to be removed. These can be found in a variety of places, including machines, valves, and specialized applications. Many Pipelines have Breakout Flanges placed at regular intervals where maintenance is required. Flanges, gaskets, and bolts are the three separate but interconnected components of a flanged joint.

Flanges Materials

Pipe flanges come in a variety of materials, including stainless steel, cast iron, aluminum, brass, bronze, and plastic, but the most common is forged carbon steel with machined surfaces.

Furthermore, flanges, like fittings and pipes, are sometimes internally furnished with layers of materials of a completely different quality than the flanges themselves, referred to as "lined flanges," for specific reasons. A flange's material is usually determined when the pipe is chosen; in most circumstances, a flange is made of the same material as the pipe.

Unless otherwise stated, all flanges addressed on this website fall under the ASME and ASTM standards. Dimensions, dimensional tolerances, and other parameters are described in ASME B16.5, while material characteristics are described in ASTM.

Types of Flanges

Flanges aren't a one-size-fits-all kind of thing. Aside from sizing, choosing the right flange design for your piping system and intended use will ensure dependable operation, a long service life, and the best price.

Here's a rundown of the most popular flange kinds.

  • Welding Neck Flanges
  • Welding Neck Flanges are easily identified by their long tapered hub that gradually transitions to the wall thickness of a pipe or fitting. The long tapered hub serves as a vital reinforcement in a variety of applications that need high pressure, sub-zero, and/or higher temperatures.

    Under conditions of repetitive bending caused by line expansion or other variable forces, the smooth transition from flange thickness to pipe or fitting wall thickness provided by the taper is particularly useful. These flanges are bored to match the inside diameter of the matching pipe or fitting, ensuring that product flow is not restricted.

    This lowers erosion by preventing turbulence at the junction. They also include a tapered hub that distributes stress well and can be easily radiographed for flaw detection. With a single full penetration, V weld, this flange will be welded to a pipe or fitting.

  • Slip-on Flange
  • A Slip-On flange's calculated strength under internal pressure is roughly two-thirds that of Welding Neck flanges, and their fatigue life is around one-third that of the latter. Two fillet welds are used to attach the flange to the pipe, one on the outside and one on the inside.

    On the image, the X measurements are rough: +3 mm pipe wall thickness To avoid damaging the flange face during the welding operation, this gap is required. One downside of the flange is that it requires the welding of a pipe first, followed by the fitting. Because named fittings lack a straight end that can fully be slipped into the Slip-On flange, a combination of flange and elbow or flange and tee is not possible.

  • Socket Weld flanges
  • Socket weld Flange was designed for use on small-diameter high-pressure pipework at first. They have the same static strength as Slip-On flanges, however, they have a 50% higher fatigue strength than double-welded Slip On flanges.

    The pipe connection is made with a single fillet weld on the flange's exterior. However, before welding, a space between the flange or fitting and the pipe must be formed.

    The pipe or tube shall be inserted into the socket to the maximum depth and then withdrawn approximately 1/16" (1.6 mm) away from contact between the end of the pipe and the shoulder of the socket in the assembly of the joint before welding, according to ASME B31.1 1998 127.3 Preparation for Welding (E) Socket Weld Assembly.

    The bottoming clearance in a socket weld is commonly used to alleviate residual tension at the weld's root that may occur during the weld metal's solidification. The graphic depicts the expansion gap's X measurement.

  • Lap Joint Flange
  • Lap Joint Flanges have the same common dimensions as any other flange on this page, but they don't have a raised face. They're utilised with a "Lap Joint Stub End." With the exception of a radius at the intersection of the flange face and the bore to allow the flanged portion of the Stub End, these flanges are almost identical to Slip On flanges.

    Their pressure-holding ability is just marginally greater than Slip On flanges, and the assembly's fatigue life is a tenth of that of Welding Neck flanges. They can be used at any pressure and come in a variety of sizes. These flanges are not welded or otherwise attached to the pipe they simply slip over it.

  • Blind Flanges
  • Blind flanges are simply boltable blank discs that are used to terminate or isolate pipe systems. When properly fitted and combined with the appropriate gaskets, they can provide an excellent seal that is simple to remove when needed.

    Flanges for Specialty Applications

    The most frequent flange types are those listed above. There are, however, a variety of other specialty flange types to suit a variety of applications and situations. Nipoflanges, weldoflanges, expanding flanges, orifice, long weld neck, and decreasing flanges are some of the other alternatives.


    This article will teach you the fundamentals of flange design and how to select the best flange for your piping system. It's hard to mention every design, feature, or consideration because there are so many stainless steel flanges and other flange materials available.

    But we at Amardeep steel helps you choose the right kind of steel for your piping solution. Keep reading our blogs and learn more about steel from our end and we are always welcome to solve and help you choose the right product for your project.

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