Flange: Types, Characteristics, Working Procedure, Application

Flanges are essential parts of numerous mechanical systems. They provide a mechanical mechanism for attaching or assembling components such as pipes, fittings, and valves. Furthermore, they may be dismantled when necessary, making them perfect for use with systems that require maintenance.

Flange Types, Characteristics, Working Procedure, Application
Flange Types, Characteristics, Working Procedure, Application

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What is a Flange?

Flanges, or rims, are symmetrical disc-like components used to connect or seal pipes, containers, or fixed-shaft mechanical elements. These disc-shaped components are most commonly seen in plumbing and are usually used in pairs. There are several types of fasteners, and threaded fixings are utilized to secure the flanges in place. In addition, a flange has bolt holes. Two flanges are often linked to pipe ends with a gasket in between, and the connection is secured using bolts.

Flanges join pipes, valves, pumps, fittings, and other equipment, including filters and pressure vessels. The flanges are either welded or threaded and bolted together with gaskets to create a seal and allow for easy access to piping systems.

Flanges have varying pressure and temperature ratings to accommodate different materials. The appropriate flange for a piping application is determined by the needed strength.
Flanges exist in many shapes and sizes and are widely employed in industries worldwide. Choosing the perfect product for your needs might be challenging due to numerous options and specs.

Flange standards vary globally, facilitating functionality and interoperability. Common standards include ASA/ASME (USA), PN/DIN (Europe), BS10 (UK/Australia), and JIS/KS (Japan/Korea).

Characteristics of Flange

Flanges are vital components in piping systems, and they have several important characteristics that improve their functionality:

  • Flanges are supplied with precisely drilled holes, allowing for quick and exact assembly with other piping elements. This function speeds up installation procedures, reducing the possibility of misalignment or poor fitting.
  • Flanges are manufactured with a method that regulates grain flow, increasing their strength and stiffness. This structural integrity allows flanges to endure the rigors of pressure and forces within pipe systems, lowering the risk of deformation or failure.
  • Flanges are designed with machined bevels to improve welding processes. These bevels ensure smooth transitions between the flange and adjacent pipes, resulting in uniform and secure weld connections. Proper welding techniques are critical for ensuring the integrity and leak resistance of the piping system.
  • Flanges have a smooth and perfectly bored inner surface to allow for uninterrupted flow throughout the piping system. This design reduces frictional losses and pressure differentials, allowing for efficient fluid conveyance without blockages.
  • Flanges are equipped with spot-facing, a machining procedure that ensures the flatness and squareness of the flange surface where fasteners are installed. This guarantees solid fastening and even distribution of bolt loads, reducing the possibility of leaks or loosening over time.

Types of Flange

Weld Neck Flange

  • Weld neck flanges feature a long tapered hub, typically machined from a forging to ensure structural integrity.
  • They are commonly used in high-pressure and high/low-temperature applications where maintaining a continuous flow of fluid through the piping system is crucial.
  • By welding the flange to the pipe, weld neck flanges provide a strong and leak-resistant connection, minimizing the risk of pressure drops, turbulence, and erosion/corrosion of metals near the joint.

Long Welding Neck Flange

  • Design: Long welding neck flanges are similar to weld neck flanges but have an extended neck, acting as a boring extension.
  • They are designed to replace weld neck flanges and pipe pieces for bolt-up connections to vessels like ships, columns, or barrels, reducing stress on the neck and transferring it to the base.
  • These flanges are often employed in connecting large networks of pipes subjected to high pressures, offering reliability and durability in demanding industrial environments.

Slip-On Flange

  • Slip-on flanges are connected to the pipe by sliding the pipe into the flange and welding it both inside and outside.
  • They are cost-effective and easy to install, making them popular for applications with low pressure and minimal risk of leakage.
  • Despite their simplicity, slip-on flanges find extensive use in various industries due to their versatility and compatibility with different pipe materials.

Threaded Flange

  • Threaded flanges have tapered threads that allow them to be screwed onto pipes without welding.
  • They are commonly utilized in low-pressure and low-temperature environments, such as water and air utility services, where welding may not be feasible or desirable.
  • Threaded flanges are particularly suitable for explosive environments like gas stations and plants, where welding connections could pose risks.

Socket Weld Flange

  • Socket weld flanges are attached to the pipe using a single fillet weld held outside the flange.
  • They are primarily used in small-size high-pressure pipes, providing a secure connection without the need for additional threading or welding inside the bore.
  • Socket weld flanges may corrode in the gap between the pipe end and the socket shoulder, making them less suitable for highly corrosive fluids or critical services.

Lap Joint Flange

  • Lap joint flanges have a flat face and are used in conjunction with a stub end. The flanges slip over the pipe and seat behind the stub end, held together by bolt pressure.
  • These flanges offer freedom of movement around the pipe, facilitating opposing flange bolt holes. They are particularly advantageous for stainless steel or nickel alloy pipelines due to their cost-effectiveness.

Blind Flange

  • Blind flanges have no bore center and are employed to terminate or seal the end of a piping system. They withstand significant mechanical stress and are suitable for high-pressure applications.
  • Their design allows easy access to the pipeline for maintenance activities, as they can be easily unbolted by operators to perform tasks inside the terminal end.

Orifice Flange

  • Orifice flanges are used in conjunction with orifice plates to measure or restrict pressure or flow in pipelines accurately.
  • They are identifiable by a hole drilled through the face perpendicular to the pipe, allowing for the installation of orifice plates for flow measurement.
  • Orifice flanges play a critical role in accurately determining fluid or gas flow rates within a piping system, making them essential in various industrial processes.

Nipo Flange

  • Also known as weldoflange, the nipo flange is a solid piece of forged steel that combines a welding neck flange with a weldolet or nipolet.
  • These flanges are utilized to branch pipelines at 90 degrees and are available in various materials to suit different operating conditions.
  • Reinforced nipo flanges offer additional mechanical strength compared to standard flanges, ensuring reliability in demanding applications.

Swivel Flange

  • Swivel flanges enable bolt holes to align between two mating flanges, facilitating installation in various pipeline applications, including large-diameter pipelines and subsea operations.
  • Available in various shapes and material grades, swivel flanges offer versatility and reliability in oil, gas, hydrocarbon, water, and chemical handling applications.

How does Flange Work?

A flange is a protruding rim, lip, or rib used to strengthen or attach pipes, valves, and other equipment to form a pipeline system, as well as to give an easy access point for cleaning, inspection, or modification.

Flange Attachment Methods and Applications

  • Flanges can be welded or screwed on, depending on the type of flange and the piping system specifications. When choosing a flange type, consider pressure capability, pipe size, and intended application.
  • Ring or slip-on flanges feature a central hole and slide onto the pipe end. The flange face extends beyond the pipe end and will be welded into place.
  • Ring or slip-on flanges feature a central hole and slide onto the pipe end. The flange face extends beyond the pipe end and will be welded into place.
  • Socket weld flanges are designed for tiny, high-pressure applications. The pipe is placed into one end, and a fillet weld is done to the exterior of the flange. To reduce weld stress, an expansion gap is necessary between the flange and the pipe.
  • Weld neck flanges have a long, tapered hub that provides strength and enhanced stress distribution for use in high-pressure, sub-zero, or elevated-temperature environments.
  • Blind flanges are flat, without a bore, and are used to complete a piping system.
  • Lap-joint flanges are similar to slip-on flanges, but they are used in combination, meaning that the flange does not come into touch with the medium in the pipe. These flanges do not require welding, thus they can spin freely to align with the matching flange.
  • Threaded flanges are commonly used for smaller pipe sizes and do not require welding, making them a practical choice; nevertheless, they are not appropriate for piping systems with thin walls.

Flanges also undergo different surface finishes to meet specific requirements:

  • Smooth Finish: Provides a flat and even surface suitable for applications where sealing integrity is essential.
  • Serrated Finish: Characterized by small grooves on the flange face, serrated finishes enhance grip and help maintain a secure seal, especially in high-pressure or high-vibration environments.

Selection of Flange Material

The choice of flange material is crucial since it has a direct impact on the connection’s performance, durability, and reliability. Here’s an overview of common flange materials and their properties:

  • Steel is widely recognized as the most popular and preferable flange material because to its high strength. Steel flanges are strong and reliable, making them ideal for a wide range of applications requiring long-term endurance.
  • Stainless steel flanges are preferred for their better resistance to corrosion and rust, making them appropriate for locations where moisture or corrosive substances may be present. They are long-lasting and preserve their integrity even under extreme situations.
  • Aluminum flanges are popular in applications where weight is an important consideration due to their lightweight qualities. Despite being lightweight, aluminum has high corrosion resistance, making it useful for a variety of industrial applications.
  • Ductile iron flanges are a low-cost alternative for backing flanges where direct contact with the medium is not required. While not as corrosion-resistant as stainless steel, ductile iron offers comparable strength and durability at a lower cost.
  • Cast iron is created by combining iron with silicon, carbon, and a variety of other alloys. Cast iron has numerous qualities, including machinability, castability, and fluidity.
  • Brass: It is a zinc-copper alloy that may also contain tin or lead. It has good conductivity, cold ductility, high-temperature ductility, and strength.

Coatings are applied to protect flanges from corrosion and damage:

Light Oil or Rust-Prohibiting Material: Applied to prevent surface oxidation and rust formation during storage and transportation.
Zinc: Offers corrosion resistance by providing a protective barrier against moisture and environmental elements.
Paint: Adds a layer of protection and can also serve aesthetic purposes.
Epoxy: Provides excellent corrosion resistance and chemical resistance, ideal for demanding environments.
Galvanized: Involves applying a layer of zinc to the surface to enhance corrosion resistance, particularly in outdoor or marine applications.

Flange Standards

ANSI/ASMEIndustry standard for pipeline flanges in the United States. Covers dimensions, materials, pressure capabilities, and more.
MSSPertains to large-diameter carbon steel flanges used in high-pressure oilfield applications.
APIPertains to large diameter carbon steel flanges used in high-pressure oilfield applications.
AWWASet of standards specific to the waterworks industry, covering aspects related to water treatment and supply.
DINEuropean metric standards are used internationally, particularly prevalent in maritime applications.

Flange Dimensions and Considerations for Choosing the Right Sizes

Apart from the functional design of a flange, flange dimensions are the most likely aspect that influences flange selection when constructing, maintaining, or updating a piping system.

To guarantee adequate sizing, you must consider how the flange interfaces with the pipe as well as the gaskets used.

Flange Dimensions
Flange Dimensions
[Image source: https://waykenrm.com/blogs/what-is-a-flange/]

Common considerations include:

  • Outside diameter: It is the distance between the two opposing sides of the flange face.
  • Thickness: The thickness of the outer adhering rim.
  • Bolt Circle Diameter: The distance between opposing bolt holes, measured from center to center.
  • Pipe size: A identification of the pipe size that the flange relates to.
  • Nominal bore size: A measurement of the flange connector’s inner diameter.

Purpose of Flange

The primary purpose of a flange is to facilitate the secure and reliable connection of pipes, valves, pumps, or other equipment at a joint.

Connection: Flanges are essential connectors that enable the assembly of parts at a joint. One flange is fixed to the equipment’s or pipe’s outside, while the other flange is placed on the other side of the joint. The flanges are firmly fastened together with bolts and nuts, guaranteeing a strong connection.

Durability: Flanges protect a range of factors that may be present in the system, including pressure, temperature changes, and mechanical stresses. Because of their structural integrity, pipelines and other equipment can successfully endure high pressures and temperature variations.

Sealing: Creating a tight seal at the joint is one of the main purposes of flanges. Liquid or gas leaks within the pipelines are stopped by gaskets or sealing materials positioned in between the flanges. Ensuring operational safety, avoiding environmental contamination, and adhering to regulatory standards all depend on this.

Flexibility: Smooth transitions between various pipe diameters, pressure classes, or materials are made possible by flanges. They are used at the interfaces between different systems or components to guarantee compatibility, smoothly integrate different components, and provide flexibility in the configuration and design of the system.

Video on Flange

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  • https://www.unifiedalloys.com/blog/flanges-101
  • https://yenaengineering.nl/what-is-flange/
  • https://www.gamak.com/en/what-is-a-flange-types-of-flanges-and-their-applications
  • https://www.kencotubes.com/blog/different-types-of-flanges-and-their-application/
  • https://www.essentracomponents.com/en-us/news/solutions/general-protection/a-guide-to-flanges
  • https://apiint.com/guide-to-flanges/

About Author

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Kabita Sharma

Kabita Sharma, a Central Department of Chemistry graduate, is a young enthusiast interested in exploring nature's intricate chemistry. Her focus areas include organic chemistry, drug design, chemical biology, computational chemistry, and natural products. Her goal is to improve the comprehension of chemistry among a diverse audience through writing.

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