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What Are Large Diameter Flanges and How Do They Work?

In large systems, two types of flanges are usually used: large diameter weld neck, slip-on, and blind. The butt welding flange and slip-on flange types are well-known common large diameter flange choices, even though the uses and structural range of the flat welding large diameter flange and the butt welding large diameter flange differ.


Large diameter flat welding flanges are less suitable for high-pressure applications as compared to weld neck counterpart. The simple ring style is appropriate for low-pressure settings. A weld neck flange is a flange with butt welds. It is appropriate for high temperature and pressure conditions as stated by the ASME B16.47 standard. Large diameter flanges are widely utilized in the water and sewage sector, wind power industry, chemical industry, and machinery industry.


Carbon steel that has been thoroughly forged and surfaces that have been machined is the most frequent material utilized to make large diameter flanges. These flanges can be manufactured in various ways. Some have raised faces, while others do not. Pretty much every single type of flange has a seal connected to it to prevent pipeline leakage.

NPS 26 through NPS 60 are included in the ASME/ANSI B16.47 Large Diameter Steel Flanges. For flanges of this size, the standards specify testing, marking, tolerances, dimensions, materials, temperature ratings, and pressure ratings with rating class designations of 2500, 1500, 900, 600, 300, 150, and even 75# for Series B compact type flanges.


The accessibility of large diameter flanges, in addition to their use with larger pipes, has permitted their use in industries such as engineering units, food industries, oil and gas industries, power generation, cement industries, cement manufacturing, and so on.


Below are some of the advantages of large diameter flanges:

  1. Large diameter flanges that have been appropriately installed are highly resistant to corrosion and have a wide range of applications.
  2. Because of their ease of installation, they can be used in any environment. Because of their large sealing surface areas, they are simple to attach, even underwater.
  3. The use of elastomeric sealing gaskets extends the life of these flanges to at least 50 years.
  4. When appropriately constructed, they provide long-term protection against corrosion, abrasion, and impact to ensure continuous proper functioning.


Large diameter flanges are often used to support and connect tank equipment and large-scale furnaces. This type of equipment is often created as a small-batch or single-piece production run rather than as a commodity production run. In the case of plate flanges, the traditional method is to cut the round plate to the size of the entire steel plate. After that, the inner circle of the round plate must be cut off. This processing technique is easy, but it necessitates a considerable amount of black space and operational space. Therefore, it is beneficial to include a large diameter flange, which results in less material usage. For large diameter slip-on with hubs and weld necks, forgings are necessary.

The flange needs to be drilled using bolt holes to match a rubber sealing ring and then another flange is installed in the center. End-user applications often demand a large flange flatness tolerance to ensure the sealing effect, and the total thickness of the flange plays a supporting function. As a result, the dimensional tolerance and roundness of the flange’s outer and inner holes are not as high as in smaller flanges.

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