How Does a Pipe Flange Work in a Plumbing System? - Merit Brass

16 Jun.,2025

 

How Does a Pipe Flange Work in a Plumbing System? - Merit Brass

What Does a Pipe Flange Do in Plumbing?

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If you've got customers asking you why you need a pipe flange in a particular location, you might be wondering what the right answers are to their questions.  Fortunately, we've collected the details so that you don't need to - you can just point them to this post.  In this post, we'll talk about what a pipe flange is, the different types, where they tend to be located, whether they're considered fittings, and how to select the right pipe flange for your application.

What is a Pipe Flange?

Used to connect pipe sections, flange faces bolt together to create a strong, watertight connection that will hold up well under high temperature or high pressure applications. It creates a much stronger joint than simply using a coupler or other pipe fittings to connect two pieces of threaded pipe, such as fitted iron pipe systems.

However, there is a wide range of different flange types, designed to meet a range of disparate plumbing standard sections, such as ASME B16.47 or ASME B16.5. One common feature is bolt holes in the flange facing, which allow the flange to be securely fastened to the surrounding material. In the next section, we'll discuss different types of pipe flanges that you may encounter.  Pipe flanges also come in several alloys some of which include:  stainless steel, brass, chrome-plated brass, copper & carbon.

What Are the Different Pipe Flange Types?

  • Weld Neck Flange - As the most commonly-used flange in process piping, a weld neck flange provides the highest joint integrity, because the butt weld that is created with the piece protruding from the raised face provides a strong bond. However, it can be bulky and cumbersome compared to other flange types, but is also available as a long welding neck flange.
  • Slip On Flange - A slip on flange matches the outer diameter of the pipe, with two locations for fillet welding to create a strong bond. With a moderate cost, it's typically used for low-pressure and temperature applications.
  • Ductile Iron Backup Flange - Often used in high pressure settings, typically between 150 and 250 PSI, a ductile iron backup flange is a relatively simple flange. It features a flat flange facing paired with a beveled edge at the center hole.
  • Threaded Flange - Typically used in utilities as well as in lower temperature and pressure applications for air and water, a threaded flange has a National Pipe Thread female connection and is available in thread sizes up to 4", providing a relatively inexpensive option for a number of situations.
  • Socket Weld Flange - Also used in lower temperature and pressure ranges, the socket weld flange has a stopping point, from which the pipe is pulled back slightly to allow for expansion. The pipe can then be welded around its circumference to the face of the flange.
  • Lap Joint Flange - If tight spaces and an expectation of frequent dismantling is a possible issue, a lap joint flange is a decent option. Consisting of two separate pieces, a ring with bolt holes and a stub that can be welded to the pipe a short distance from the ring, the butt weld created is stronger, while the stub allows the pipe to be turned while welding.
  • Blind Flange - Sometimes used as manhole covers for vessels, a blind flange has no hole for air or gas to pass through. It's also commonly used to end runs of pipe, effectively isolating the run from other systems.
  • Swivel Flange - Designed to speed up installation, a swivel flange makes it easy to align bolt holes on a pair of flanges. Because the flange is able to swivel around the circumference of the pipe, it can easily be moved to match a welded flange's bolt positioning.
  • Expanding Flange - When a pipe needs to change to a larger size, an expanding flange provides an effective way of managing the change. It features a widening stub that the larger pipe can be joined to, making it a popular choice for retrofit projects.
  • Reducing Flange - When there needs to be a change in the side of the pipe to a smaller pipe, a reducing flange has a tapered raised face for a butt weld. Providing an economical way to reduce pipe size at a particular point, they're used in a range of applications.
  • Nipoflange/Weldoflange/Elboflange/Latroflange - Most commonly used in high-pressure situations, these types of specialty flanges create a unique nipple that protrudes markedly from the flange facing. Its installation requires fewer welds, while still maintaining superior strength.
  • Plate Flange - An economical alternative to heavier ANSI flanges.  Plate flanges are suitable for low pressure, less critical applications.  They have a serrated surface to enhance sealing properties.  There are several types of plate flanges:  blind, tube OD slip-on, IPS slip-on bevel x square and IPS slip-on square x square.

Where are Pipe Flanges Located?

Generally speaking, a pipe flange is located at points where regular disassembly, maintenance, or cleaning will be taking place. This can include making it possible to bolt pipe systems directly to equipment, fittings, or other features quickly, easily, and securely.

Are Pipe Flanges Considered Fittings?

Pipe flanges are considered a very popular type of fitting in plumbing systems, and are often used when pipes are used for non-plumbing systems as well, such as railings, racks, and similar applications. However, they often provide an additional level of security to the fitting, because the bolt holes allow the fitting to be secured to the surrounding structure.

How Do I Choose the Right Pipe Flange?

Pipe fittings will vary based on your application. However, by having a better grasp of how pipe flanges work, you'll be able to answer your customers' questions much more easily, improving their confidence in your ability to do the job they've hired you for. If you're looking for expert advice, contact Merit today for more details. 

STILL HAVE QUESTIONS?

SOURCES INCLUDE:

https://hardhatengineer.com/types-flanges-used-piping 

https://www.unifiedalloys.com/blog/flanges-101 

https://www.apiint.com/resource-center/introduction-to-flanges 

Haihao Group are exported all over the world and different industries with quality first. Our belief is to provide our customers with more and better high value-added products. Let's create a better future together.

https://www.punchlistzero.com/swivel-flange 

3/28/ 1:48:38 PM

Flange 101: Understanding the Basics - Titan Fittings

A Comprehensive Guide to Flange Basics

Flanges link pipes, valves, and other elements in piping networks. They ensure a leak-proof bond and are essential for many applications. A flange connection involves two pieces affixed to pipe ends, bolted or welded together. This firm fastening also allows for straightforward disassembly if bolted together. With certain variations, such as sanitary flanges, a gasket is used to ensure a secure seal. Flanges are available in diverse materials like carbon and stainless steel, suiting various uses and settings. This article delves into flanges, discussing their relevance, categorization, sizes, and beyond. Continue reading as we decode a key element of our contemporary infrastructure.

Usage of Flanges

Flanges fulfill multiple critical roles in piping networks. They facilitate the easy joining of pipes for a leak-free bond and provide a seal surface to avert fluid escape. Flanges also bolster pipelines, spreading the load among flange bolts, and uphold structural soundness. They help in managing and directing fluid movement by incorporating valves or other flow-regulating devices. Key to numerous sectors like manufacturing, petrochemical, and plumbing, flanges are crucial for joining and separation in piping systems. These components ensure a robust, leak-free junction, facilitating fluid transport safely and efficiently.

Flanges' Significance in Plumbing & Piping

In piping networks, flanges are pivotal for assembly purposes. They avert leaks in pressurized settings, enabling secure fluid movement in industrial contexts. Flanges are crucial for enabling smooth pipe connections. Flange usage boosts efficiency and safety in varied applications, underscoring their importance in piping realms.

Knowing face types and material is essential across many industrial applications. As an example, stainless steel flanges guarantee extended usability and durability, particularly in petrochemical projects. With adherence to ASME and ASTM standards, production quality can be maintained.

Examining Flange Varieties: An In-Depth Look

Investigating the array of pipe flange types, each with distinct characteristics and uses. Delving into standards by bodies like the American Society of Mechanical Engineers (ASME) and the American Society for Testing and Materials (ASTM) to assure quality and compatibility in piping networks.  Flanges designed for hydraulic applications are also made to the SAE standard J518/ISO .

1) Slip-On Flanges

Slip-on flanges are commonly employed in piping systems for their ease of installation, cost-effectiveness, and versatility. These flanges, which slide over the pipe before being welded, are particularly advantageous in scenarios where quick installation and reduced material costs are priorities, as they do not require matching the pipe's thickness. While they are suitable for a range of applications, including both high and low temperatures and pressures, slip-on flanges are less ideal for high-pressure or high-temperature conditions compared to other flange types like weld neck flanges. Their lighter weight and easier alignment process further contribute to their utility in moderate conditions, making them a practical choice for non-critical, lower-pressure services.

2) Socket-Weld Flanges

Socket-weld flanges are used primarily in smaller diameter, high-pressure piping systems. They are designed to provide a strong, reliable connection where the pipe is inserted into a recessed area of the flange, known as the socket, and then welded. Socket-weld flanges are particularly beneficial in piping systems that require a smooth flow of fluid without any significant turbulence, which is often a requirement in chemical, petrochemical, and steam applications. Their design helps in reducing the possibility of leakage and is ideal for applications where the risk of fluid leakage must be minimized, such as in high-pressure and high-temperature environments. Additionally, they offer ease of alignment and assembly, which can be advantageous during the installation process.

3) Lap Joint Flanges

Lap joint flanges are particularly useful in piping systems that necessitate regular disassembly and maintenance, as they facilitate easy alignment and access. Comprising two parts, the stub end and the flange, these flanges allow for easy assembly and disassembly: the stub end is welded to the pipe while the flange fits over it. Their design enables the flange to rotate, simplifying bolt hole alignment, especially beneficial in complex or large pipe systems. Ideal for applications with expensive or lined pipes, lap joint flanges are cost-effective since only the stub end needs to match the pipe material or lining, allowing for a less expensive material for the flange itself. This makes them a practical choice for systems requiring frequent inspection, cleaning, and in scenarios where installation ease and cost-effectiveness are key considerations.

4) Weld Neck Flanges

Weld neck flanges are extensively employed in industrial settings requiring high-pressure tolerance, such as chemical processing plants, power generation facilities, and construction sites. They are designed for secure and durable connections between pipes, valves, and other components in a piping system. Available in various types like standard long, extra long, integral, and nipoflange, each serves specific applications ranging from low-pressure environments to heavy-duty systems and connections where welding is impractical. Their key advantage lies in their robust, leak-proof design, offering long service life and stress reduction, crucial in high-pressure scenarios.

5) Blind Flanges

Blind flanges are solid discs used predominantly to seal off pipeline ends, providing an effective means of preventing fluid or gas escape in various systems. Widely utilized in industries such as water systems, chemical manufacturing, and construction, blind flanges facilitate pipeline extensions and are invaluable in pressure testing. They are designed for high-pressure environments and are available in various materials like A36 steel plate and stainless steel, catering to specific requirements. The installation of blind flanges involves ensuring a clean and smooth pipe end before attaching the flange with bolts for a secure seal.

6) Sanitary Flanges

Sanitary flanges, predominantly utilized in the pharmaceutical, biotech, and food and beverage industries, are designed for applications where cleanliness and sterility are paramount. These flanges facilitate quick assembly and disassembly for regular cleaning and maintenance, ensuring hygiene standards are upheld. Characterized by their smooth, non-contaminating surfaces, sanitary flanges prevent the accumulation of bacteria and other contaminants. Their design adheres to strict industry standards, such as those set by the 3-A Sanitary Standards and ASME-BPE, to ensure the integrity and quality of products passing through the piping systems.

Frequently Asked Questions

What are flanges?

Flanges are ring-like fittings used to connect pipes, valves, pumps and other equipment in a piping system.  They provide easy access for cleaning, inspection or modification.

How do I choose the right stainless steel flange for my application?

Choosing the right flange depends on several factors, including the size and type of the pipes being connected, the pressure and temperature of the system, the fluid being transported and the specific environmental conditions. When choosing between stainless steel and carbon steel for a flange, consider the operating environment and requirements. Stainless steel offers superior corrosion resistance and is ideal for harsh, acidic, or chlorine-rich environments, but it's more expensive. Carbon steel, being stronger and more cost-effective, is suitable for high-pressure applications and less corrosive environments. Additionally, consider factors like temperature tolerance, weldability, maintenance needs, and industry-specific standards in your decision. Refer to the above guide to review the different types of flanges and their typical applications.

How are flanges installed?

The installation of steel and/or stainless steel flanges involves aligning the flanges on either end of the pipes, inserting the appropriate gasket between them and then securing the assembly with bolts.  The specific installation process can vary depending on the flange type and the application.

Conclusion

In the realm of modern infrastructure, flanges are essential for creating robust, leak-proof connections in piping systems across various industries. They come in different forms, including slip-on, socket-weld, lap joint, weld neck, blind, and sanitary flanges, each tailored to specific applications. The material versatility of flanges ensures adaptability across diverse environments. This guide underscores the importance of understanding the unique features and proper use of each flange type, demonstrating their indispensable role in ensuring the integrity, efficiency, and safety of global piping networks.

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