An In-Depth Exploration of Types of Forged Flanges in Piping Systems

Types of Forged Flanges

An In-Depth Exploration of Types of Forged Flanges in Piping Systems

Forged flanges represent a crucial component in the assembly of piping systems, ensuring the reliable connection of pipes, valves, pumps, and other equipment across many industrial and commercial applications.

As a vital element of modern infrastructure, understanding the role and significance of forged flanges is essential for engineering, construction, and related professionals.

This blog will discuss their manufacturing process, advantages, and the different types available to cater to specific project requirements.

What is a forged flange?

Forged flanges are mechanical components used to connect pipes, valves, pumps, and other equipment in piping systems. They are made through the forging process, which involves heating a metal material, usually, steel, to a high temperature and then shaping it by applying force, either by hammering, pressing, or rolling. Forging produces strong, durable flanges that withstand high pressures, temperatures, and stresses.

Different types of forged flanges

The most common ones are some standard forged flanges.

Weld Neck Flange

A weld neck flange is a type of forged flange designed to provide a strong and reliable connection in piping systems. It is characterized by its long, tapered neck (also known as a hub) that extends from the flange’s main body.

Types of Forged Flanges

The neck’s tapered design provides reinforcement, reduces stress concentrations at the base, and facilitates a smooth transition between the flange and the pipe, reducing turbulence and erosion.

Weld neck flanges are welded to the pipe by a circumferential weld around the neck. This welding technique creates a robust, leak-proof connection suitable for high-pressure, high-temperature, and highly fluctuating conditions. The weld neck flange’s internal diameter is designed to match the pipe’s internal diameter, ensuring optimal flow and minimal turbulence.

Slip-On Flange

As the name suggests, slip-on flanges simply slide over the pipe and are then welded in place. They are connected to the pipe by two fillet welds: one on the inside and one on the outside of the flange. This welding technique creates a strong connection but is not as robust as the weld neck flange’s circumferential weld.

Types of Forged Flanges

Socket Weld Flange

A socket weld flange is a kind of forged flange designed for small-bore, high-pressure piping systems. It features a recessed socket or bore in the flange, which the pipe is inserted into before welding.

Types of Forged Flanges

The pipe is typically inserted until it reaches a pre-determined distance from the bottom of the socket, creating a small gap known as the expansion gap. This gap allows for thermal expansion and prevents the pipe from cracking due to temperature fluctuations.

A single fillet weld around the outer diameter of the pipe forms the connection between the pipe and the flange. This welding technique creates a strong connection suitable for high-pressure applications but is less resistant to fatigue than the weld neck flange’s circumferential weld.

Lap Joint Flange

A lap joint flange is a type of forged flange specifically designed for use with a separate component known as a stub end, a short pipe with a flared or lap-joint end. The lap joint flange is not welded to the pipe directly; instead, it is free to rotate around the stub end, which is butt-welded to the pipe. This design allows for easy alignment and disassembly, making lap joint flanges ideal for systems requiring frequent maintenance, adjustments, or cleaning.

Types of Forged Flanges

Some advantages of lap joint flanges include the following:

  1. Easy alignment and disassembly: Since the lap joint flange is not welded to the pipe, it can be easily rotated for alignment with other flanges. The system can be disassembled without cutting or grinding the flange welds.
  2. Reduced stress on piping: The lack of a direct weld connection between the lap joint flange and the pipe results in less stress being transferred from the flange to the pipe, which can help reduce the likelihood of stress-related failures in the piping system.

Threaded Flange

A threaded flange is a type of forged flange with a threaded bore designed to connect with pipes with matching external threads. This unique design allows for easy installation and disassembly without the need for welding, making it particularly suitable for low-pressure applications and systems that require frequent maintenance and adjustments or where welding is not feasible.

Types of Forged Flanges

Some key features of threaded flanges include:

  1. No welding required: Threaded flanges can be screwed onto the pipe, eliminating the need for welding and simplifying the installation process.
  2. Easy assembly and disassembly: The threaded connection allows for quick and easy assembly and disassembly, making it ideal for systems that require regular maintenance or adjustments.
  3. Compatibility: Threaded flanges are available in various sizes, pressure ratings, and materials to suit a wide range of applications. They are manufactured according to different standards, such as ASME/ANSI, DIN, JIS, BS, and ISO, ensuring compatibility and interchangeability with other components.

Blind Flange

A blind flange is a type of forged flange designed to seal the end of a piping system or pressure vessel, providing a secure and reliable closure. It is a solid, flat disc with no bore, and its primary purpose is to block off the flow through a pipe or provide a means to access the interior of the system for maintenance, cleaning, or inspection.

Types of Forged Flanges

Blind flanges are commonly used in various industries, including oil and gas, petrochemical, power generation, and water treatment, to provide secure closures for piping systems or pressure vessels, facilitate pressure testing, or allow access for maintenance and inspection.

Long Welding Neck Flange

A long welding neck flange, also known as a long weld neck flange or an LWN flange, is a type of forged flange characterized by its extended neck or hub, which is welded to the pipe.

Types of Forged Flanges

This unique design provides added support and reinforcement for the connection, making it particularly suitable for high-pressure and high-temperature applications and those requiring increased fatigue resistance or mechanical stability.

The extended neck allows for a gradual transition from the flange face to the pipe, reducing stress concentrations and enhancing the fatigue resistance of the connection.

Also, the tapered neck of the long welding neck flange provides a smooth transition from the flange bore to the pipe, reducing turbulence and minimizing flow disturbances or pressure drop.

The elongated neck of the long welding neck flange provides better reinforcement. It distributes the stress more evenly, reducing the risk of flange deformation or failure under high pressure or temperature conditions.

However, apart from these standard ones, there are also some special forged flanges as well.


A nipoflange, also known as a weldolet flange or welding outlet flange, is a combination of a weldolet (welding outlet) and a flange. It is a specialized fitting designed for creating 90-degree branch connections in a piping system.

Types of Forged Flanges

Manufactured by combining a welding neck flange with a forged Nipolet, it offers a secure and reliable attachment for auxiliary equipment, such as valves, instruments, or other pipes.

This unique design provides several advantages compared to traditional branch connections, making nipoflanges ideal for high-pressure, high-temperature applications.

The nipoflange is specifically designed for creating 90-degree branch connections in a piping system, ensuring a precise and secure connection with optimal flow characteristics.

The integral flange design, combined with the forged Nipolet, provides a strong and reliable connection, distributing stress more evenly and minimizing the risk of deformation or failure under high-pressure or high-temperature conditions.


A weldoflange is a specialized pipe fitting that combines a weldolet (welding outlet) and a weld neck flange, used to create a branch connection in a piping system.

Types of Forged Flanges

It is conceptually similar to a nipoflange, which combines a welding neck flange with a forged Nipolet. Both fittings allow for the easy and secure attachment of auxiliary equipment, such as valves, instruments, or other pipes, and are commonly used in high-pressure, high-temperature applications.

A key distinction between weldoflanges and nipoflanges is that weldoflanges are made from a single piece of solid forged steel, not by welding separate parts together. This manufacturing process results in a more robust and reliable connection, as it eliminates potential weak points or stress concentrations that can be introduced during welding.

Elboflange & Latroflange

Elboflange and latroflange are not standard or widely recognized terms in the piping and flange industry.

Types of Forged Flanges

An elboflange is a combination of a flange and an Elbolet, while a latroflange combines a flange with a Latrolet. These specialized flange fittings are used to create branch connections in a piping system while also providing a flange for the attachment of auxiliary equipment, such as valves, instruments, or other pipes.

Elboflanges are specifically used to branch a pipeline at 45 degrees, providing a smooth transition while maintaining optimal flow characteristics.

Swivel Flanges

Swivel ring flanges are designed to facilitate the alignment of the bolt holes between two mating flanges, which is particularly helpful in various circumstances, such as the installation of large-diameter pipelines, subsea and offshore pipelines, pipe works in shallow waters, and similar environments. Swivel flanges are well-suited for oil, gas, hydrocarbons, water, chemical, and other demanding fluids in petrochemical and water management applications.

Types of Forged Flanges

In the case of a large-diameter pipeline, for instance, the pipe is fitted with a standard welding neck flange at one end and a swivel flange at the other end. By simply rotating the swivel flange on the pipe, the operators can achieve perfect alignment of the bolt holes more easily and quickly.

Due to their specialized design and the additional components required (such as bearings), swivel flanges can be more expensive compared to traditional flanges.

Expanding Flanges

Expanding flanges, or “expander flanges,” are utilized to increase the pipeline bore from one point to another or connect pipes to other mechanical devices, such as pumps, compressors, and valves with different inlet sizes. The expanding flange depicted in the image is a welding neck flange with a larger bore on the non-flanged end.

Types of Forged Flanges

Expanding flanges can be used to increase the run pipe bore by only one or a maximum of two sizes and not more (for example, from 2 to 3 or a maximum of 4 inches). Expander flanges are a more cost-effective (and lighter) solution compared to the combination of a buttweld reducer and a standard flange, which is the standard solution for pipe bore increases above two sizes.

The most common materials for expanding flanges are A105 (high-temperature carbon steel), A350 (low-temperature carbon steel or LTCS), and ASTM A182 (stainless steel and above). Pressure ratings and dimensions of expanding flanges are in accordance with the ANSI/ASME B16.5 specification and are available with raised or flat faces (RF, FF).

Reducing flange

Reducing flanges, also known as reducer flanges, serve the opposite function of expander flanges, as they are designed to decrease the bore of a pipeline. These flanges are typically used when the bore reduction is limited to 1 or 2 sizes; for larger reductions, a solution combining a butt weld reducer and a standard flange is more suitable.

Types of Forged Flanges

Reducer flanges are available in a wide range of sizes and material grades, although they are not commonly found in stock. The specifications, sizes, and material grades for reducing flanges are similar to those of expander flanges.

It is important to note that while not technically a flange, spectacle blinds share some similarities in shape and function. Spectacle blinds, along with ring spacers and spades, are used between pipes to mechanically isolate the pipeline, offering an efficient and straightforward method of isolation.

Forged Flanges manufacturer

Taiyuan Forging is a renowned manufacturer of high-quality forged flanges with years of experience in the industry. We specialize in producing a wide range of flanges, including slip-on flanges, weld neck flanges, socket weld flanges, and threaded flanges.

With a strong commitment to quality and customer satisfaction, Taiyuan Forging has become a preferred choice for businesses across various industries, including petrochemical, railway system, and so on.

Taiyuan Forging’s state-of-the-art manufacturing facility is equipped with the latest technology and machinery to ensure that our flanges meet the highest quality and performance standards. We adhere to strict quality control measures and follow international standards, such as ANSI, ASME, and DIN, to guarantee the reliability and durability of our products.

If you have any inquires about forged flanges, please don’t hesitate to contact us!