Flange | Types | Specifications | Dimensions | PDF - AzinForge Co

Flange is a piece for connecting pipes and other equipment to each other, which is usually used in piping systems. This connecting part is produced in different types such as weld neck, socket weld, blind and spectacle for use in refineries, power plants, etc. Their material can be made of Carbon steel, Stainless steel, Alloy steel, Aluminum, Copper and Plastic. 

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the standards for making flanges include: ANSI, ASME, JIS, DIN, EN. According to the mentioned cases, the price of this piece also depends on factors such as the dimensions, the type of raw materials and the standard used, etc. In the continuation of this article, we will examine the types of flanges, technical specifications, how to engrave, dimensions, classes, standards, methods of producing flanges, technical specifications table based on ASME B16.5 standard and the factors affecting their prices. You can also download its PDF file at the end of this article.

The production process of cutting flange begins with smoothing the steel metal, which thins the material by means of rollers to reach the thickness of the desired plate. Then the outer diameter and inner diameter of the flange (except the blind flange) are cut using a torch, laser or water jet cutter (water pressure). The necessary screw holes and teeth are cut. Also, the flange is also machined according to the exact specifications. The flanges produced in this method have a lower production cost, but they leave more material waste and their strength is weaker than other methods.

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1- Manufacturer of Product: for example, AzinForge

2- Flange Dimension: According to ASME B16.5 standard, it can be between 1/2 inch and 60 inches (AzinForge also produces non-standard flanges according to customer requests).

3- Class: In the sense of pressure determination, it is the allowable temperature that can be tolerated for the use of a flange.

4- Bore Diameter: if there is a hole on the flange, it is engraved on it.

5- Dimensional specifications: For example, the ASME B16.5 standard has different dimensions, sizes and technical specifications that are used according to the customer’s needs.

6- Material specifications: indicates the type of raw materials used. For example, code A105, which is one of the grades of carbon steel.

7- Heat Codes: This code is engraved in the flange to determine the material specifications and tolerable temperature. Also, this code is displayed in alphanumeric form.

8- Product code: It is optionally engraved by the manufacturing companies to inquire about the flange.

The raw materials used in the manufacture of flanges can be varied and are selected depending on the type of application and the required performance conditions.

In the following, we state some common raw materials used in the manufacture of flanges.

1- Carbon Steel

This type of steel is used for many flanges. Also, carbon steel is one of the main materials used in various industries such as: construction, automobile manufacturing, tools and machinery production due to its strong mechanical properties and suitable welding capability.

2- Alloy Steel

Alloy steel is used in flanges that are used under high temperature conditions or special pressures. Especially, this type of steel is strengthened by adding alloy elements such as chromium, nickel and molybdenum.

3- Stainless Steel

Flanges that are placed in environments with high humidity (water and oxygen) may be made of stainless steel. Therefore, this type of steel has high resistance to rust and corrosion.

4- Nickel Alloys

Nickel alloysmay be used in flanges that are exposed to very high temperatures or contact with certain chemicals. Also, these alloys have high resistance to corrosion and high temperature.

5- Aluminum

Aluminum is used in some light flanges with less mechanical resistance. Also, aluminum has features such as: light weight, high thermal conductivity and corrosion resistance. Therefore, aluminum is one of the popular materials for use in various industries such as: automotive, construction, aerospace and many others.

6- Polyethylene

Polyethylene is a type of polymer that is used as a plastic material. Also, this material is widely used due to its properties such as flexibility, resistance to breaking, insulation and chemical resistance. For this reason, this material is widely used in packaging, automotive, electronics and other industries.

Other raw materials such as copper and titanium are also used in some flanges. But choosing the right raw material for the flange should be determined based on its technical characteristics and application conditions.

Weld Neck (WN) Flange is one of the types of flanges used to connect pipes or equipment in the piping system. This type of flange has a throat to connect to the pipe or other parts. Due to the extra strength and stability that this type of flange provides, it makes sense to use it in various industries. This piece is used in various industries such as oil and gas, petrochemical and chemical, etc. due to its durability and stability.

Slip On (SO) Flange   is a type of connector that is used to connect pipes or equipment to each other in industrial piping. Also, this type of flange has a non-flat external disc that is placed on the end of the pipe or equipment and is connected to it by welding. For this reason, it is a quick and easy way to connect pipes, valves, etc. in the piping system. Normally, this piece is used in low pressure applications and is suitable for gas, water and sewage industries and heating and cooling systems.

1. Factors influencing the price of flange:

The price of flanges depends on various factors such as the type of raw materials, size and dimensions, standards and their production technology. Also, demand and supply in the market have a great impact on the price of flanges.

2. Flange price determination methods:

1-2. Price of raw materials:

For example, the price of steel, iron, aluminum and other raw materials used in flange production can have a great impact on the final price. Therefore, changes in the market of raw materials can also have a direct effect on the final price of the flange. Also, accurate calculation of material cost and consideration of relevant market variables is essential.

2-2. Cost of production:

Even labor cost, production cost, shipping cost and other costs related to the production of flanges should be considered. Also, the costs of machinery and equipment used in production should also be considered in cost calculations. Therefore, in order to accurately calculate the cost of flange production, all costs related to production, including raw material costs, labor costs, machinery and equipment costs, and other costs, must be considered and collected together to calculate the final cost of flange production.

3-2. Logistics and shipping cost:

For example, the cost of transportation, packaging, insurance and other costs related to the transfer of flanges to the final destination should also be considered in calculating the final price of the product. So, these costs also have a direct impact on the final price and should be carefully considered.

As a result, to accurately determine the price of flanges, the cost of raw materials, production cost and logistics cost should be considered. This price is affected by various factors, including the type of material, dimensions, standard and production technology.

TYPES OF FLANGES

In this article, we review the 13 types of flanges for pipelines and piping systems (ASME B16.5), divided into “standard” and “non-standard” (or less common) types.

Large flange sizes, not examined here, are ruled by the ASME B16.47 Series A-B Specification.

Let’s now delve into the features of the ASME B16.5 standard types of flanges.

STANDARD TYPES (ASME)

WELDING NECK FLANGE (“WNF”)

An ASME Welding Neck Flange, often referred to as a weld neck flange (WNF), is a type of pipe flange that provides a strong, durable connection for piping systems.

A WNF is characterized by its long tapered hub, which provides important reinforcement for use in various applications, particularly those involving high pressure and temperature. This design not only facilitates stress distribution but also reduces the concentration of stress at the base of the flange, making the weld neck flange an ideal choice for critical and demanding services.

This flange type is used, normally, in high-pressure and high/low-temperature applications that require an unrestricted flow of the fluid conveyed by the piping system (the bore of the flange matches with the bore of the pipe).

Design and Features:

• Tapered Hub: The distinguishing feature of a weld neck flange is its gradually tapered hub, which transitions smoothly from the flange diameter to the pipe diameter. This design enhances strength and supports stress distribution.
• Butt-Welded Connection: Weld neck flanges are designed to be butt-welded to the pipe. The welding process creates a continuous metal structure between the pipe and flange, offering superior strength and leak integrity.
• Bore Matching: The bore of the weld neck flange is machined to match the inside diameter of the adjoining pipe, ensuring smooth flow and reducing turbulence and erosion at the joint.
• Pressure Ratings: ASME specifies various pressure classes for weld neck flanges, including but not limited to Class 150, 300, 600, 900, , and . The choice of class depends on the system’s maximum operating pressure and temperature.

Standards:

Governed by the American Society of Mechanical Engineers (ASME) under standards such as ASME B16.5 (for sizes up to 24 inches) and ASME B16.47 (for larger sizes), welding neck flanges are manufactured to these specifications to ensure compatibility and safety across a wide range of applications.

Applications:

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• High-Pressure Systems: Due to their robust design, weld neck flanges are widely used in high-pressure applications, such as steam lines, high-pressure gas pipelines, and power generation plants.
• High-Temperature Services: The integral connection between the flange and pipe makes weld neck flanges suitable for high-temperature applications, including refineries and chemical processing plants.
• Fluctuating Conditions: The strength and durability of weld neck flanges make them ideal for systems experiencing fluctuating pressures and temperatures, providing a stable, leak-proof connection.

Advantages:

• Strong and Durable: The welded joint provides a strong, high-integrity connection that is less likely to leak compared to other flange types.
• Reduced Stress Concentration: The tapered hub promotes better stress distribution, reducing the likelihood of fatigue and failure.
• High Compatibility: Suitable for a wide range of applications due to the availability of various materials and pressure ratings.
• Low-Pressure Drops: Limited to non-existing pressure drops prevent negative effects such as turbulence and erosion/corrosion of the metals in the proximity of the flanged joints.
• RX Inspections: The tapered hub allows a smooth distribution of the mechanical stress between the pipe and the weld neck flange and facilitates the execution of radiographic inspections to detect possible leakages and welding defects.

The dimension of the flange (NPS and the pipe schedule) shall match the dimension of the connecting pipe.

A welding neck flange is connected to a pipe by a single full penetration V-shaped butt weld. The dimensions and weights of ASME weld neck flanges are shown in this article.

LONG WELDING NECK (“LWNF”)

A Long Welding Neck Flange, often abbreviated as LWNF, is a specific type of welding neck flange designed for use in high-pressure and/or high-temperature applications, where additional support is required.Long weld neck flanges may be found on vessels, columns, or barrels. These flange types are available also in the heavy barrel (HB) and equal barrel (E) types.In summary, long welding neck flanges offer a robust solution for connecting pipes to critical equipment in high-stress applications. Their design provides the additional support needed to maintain system integrity under demanding operational conditions.

SLIP-ON FLANGE

A slip-on flange is a type of pipe flange that slides over the end of a pipe and is then welded on both the inside and outside to provide sufficient strength and prevent leakage.

This design allows for an easier and less precise alignment compared to some other flange types, such as weld neck flanges, making the slip-on flange a popular choice for lower-pressure and temperature applications.

Key Features:

• Ease of Installation: Slip-on flanges are easier to align than weld neck flanges, making them suitable for applications where the precise alignment is challenging.
• Welding Requirements: Requires less welding compared to weld neck flanges. The welding process involves welding around the outer diameter of the flange to secure it to the pipe and may include welding the inside diameter for additional strength and leak prevention.
• Cost-Effectiveness: Generally, slip-on flanges are more cost-effective than weld neck flanges due to their simpler design and reduced material usage.
• Versatility: They can be used with both seamless and welded pipes and are available in a variety of materials, including carbon steel, stainless steel, alloy steel, and more, to suit different applications.

Applications:

Slip-on flanges are commonly used in lower-pressure and non-critical applications, such as water distribution, heating and cooling systems, and various piping systems within commercial and light industrial settings. They are not recommended for high-pressure or high-temperature applications or for systems with a high risk of fatigue due to bending forces.

Advantages:

• Cost Efficiency: Less material is required for manufacturing, and the simpler design translates to lower costs.
• Simplified Installation: The ability to easily slide the flange onto the pipe before welding simplifies the installation process, especially in tight spaces.
• Flexibility: Suitable for various piping materials and applications where the conditions do not demand the high integrity of a weld neck flange.

Limitations:

• Lower Strength: Slip-on flanges have a lower pressure and temperature rating compared to weld neck flanges, limiting their use in high-pressure applications.
• Risk of Leakage: While less common, the potential for leakage exists if not properly welded on both sides.

Installation Considerations:

When installing slip-on flanges, it’s important to ensure proper alignment before welding and to follow appropriate welding procedures to secure the flange to the pipe. Both the inside and outside welds are crucial for the structural integrity of the connection and to prevent leaks.

A slip-on flange is connected to the pipe or the fittings by two fillet welds, one executed inside and one outside the cavity of the flange.

The bore size of a slip-on flange is larger than the outside diameter of the connecting pipe, as the pipe has to slide inside the flange to be connected by the execution of a fillet weld.

Slip-on flanges are also defined as “Hubbed Flanges” and they are easy to recognize due to their slim and compact shape.

The dimensions and weights of slip-on flanges ANSI/ASME are available on this page.

WELD NECK VS SLIP-ON FLANGE

Flanged joints made with slip-on flanges are, in the long run, a bit more fragile than connections made with welding neck flanges (in similar service conditions). This fact, observed several times on oil & gas fields, seems due to the following facts:

• a welding neck flange features a tapered hub, absent in a socket weld flange, which distributes the mechanical stress between the pipe and the flange more evenly
• a welding neck joint as only one welding area instead of two (socket weld flange).

Another advantage of the welding neck flange is that it can be connected either to pipes and fittings, whereas socket weld flanges suit pipes only.

To summarize the differences between slip-on and welding-neck flanges:

• Strength and Integrity: Weld neck flanges offer higher strength and integrity, making them suitable for severe service conditions, whereas slip-on flanges are better suited for lower-pressure and temperature applications.
• Cost and Installation: Slip-on flanges are generally more cost-effective and easier to install but may require more care to ensure a leak-proof seal.
• Application Suitability: The choice between weld neck and slip-on flanges depends on the application’s pressure, temperature, and criticality. Weld neck flanges are preferred for high-pressure and temperature applications, while slip-on flanges are adequate for less demanding conditions.

THREADED FLANGE

Threaded flanges are joined to pipes by screwing the pipe (which has a male thread, generally NPT per ASME B1.20.1) into the flange, without the need to execute seam welds (in certain cases, though, small welds are applied to increase the strength of the connection).

Threaded flanges are available in sizes up to 4 inches and multiple pressure ratings, however, they are used, mostly, small size piping in low-pressure and low-temperature applications, like water and air utility services.

Threaded flanges are also a mandatory requirement in explosive areas, such as gas stations and plants, as the execution of welded connections in such environments could be dangerous.

Consult this article, to find out about the dimensions of ANSI/ASME threaded flanges.

SOCKET WELD FLANGE

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Socket weld flanges are connected to pipes using a single fillet weld executed on the outer side of the flange (different from the slip-on flange type that requires two welds).

LAP JOINT FLANGE

SPECIAL TYPES (ASME)

The last type of forged product that resembles the shape of a flange is the so-called spectacle blind: while not properly a flange, a blind (or a ring spacer or spade) is used in between pipes to isolate the pipeline mechanically and in a very easy way. More details are provided in another section of our Wiki for piping.

EUROPEAN TYPES OF FLANGES (EN ISO)

European flanges, often specified and used within projects and industries across Europe, adhere to standards developed by European organizations (CEN, EN, ISO, DIN, etc.).

These flanges are designed to ensure compatibility, safety, and reliability in various applications, including oil and gas, chemical processing, water treatment, and power generation. The most notable standards governing European types of flanges are those issued by the European Committee for Standardization (CEN) and the International Organization for Standardization (ISO). Here’s an overview of key European flange types and their standards:

1. EN -1 Flanges

Standard: This standard specifies requirements for circular steel flanges ranging from DN 10 to DN and includes flanges for PN-designated pressures, and the PN (Pressure Nominale) numbers signifying nominal pressure in bars.

Types: EN -1 flanges come in various types, including:

• Type 01: Plate (flat) flanges for welding.
• Type 02: Loose plate flanges with weld-on plate collar.
• Type 05: Blank (blind) flanges.
• Type 11: Weld-neck flanges.
• Type 13: Hubbed threaded flanges.

Applications: Used across a wide range of industries for piping systems that transport water, oil, gas, and chemicals.

2. DIN Flanges

Before the adoption of the EN -1 standard, Germany’s DIN (Deutsches Institut für Normung) standards were widely used, not just in Germany but across Europe. Some common DIN standards for flanges include:

• DIN : Standard covers bolt dimensions and flange face dimensions for PN designated flanges.
• DIN to DIN : Specifications for weld neck flanges.
• DIN : Slip-on flanges for welding.

Applications: Although EN standards are now more commonly specified, DIN flanges are still used and recognized, especially in older systems and in projects with specific requirements.

3. BS EN Flanges

The British Standards Institution (BSI) adopts EN standards for use in the UK, such as BS EN -1, aligning with European specifications for flanges.

Applications: These flanges are used in the UK and internationally, wherever British standards are specified or required for compatibility and quality assurance.

4. ISO Flanges

ISO Standards: While not exclusively European, ISO standards for flanges, such as ISO -1, mirror and complement European standards, ensuring global compatibility and interoperability.

Types and Applications: ISO standards cover a range of flange types similar to those in EN -1, facilitating their use in international projects and applications.

Material and Pressure Ratings

• European flanges are available in various materials, including carbon steel, stainless steel, and alloy materials, to suit different environmental conditions and fluid properties.
• Pressure ratings follow the PN designation or are specified according to the applicable EN or ISO standards, ensuring that the flanges can withstand the operational pressures of the system.

European flanges, characterized by their diverse types and adherence to standardized specifications, play a crucial role in ensuring the safety, reliability, and efficiency of piping systems across a wide array of industrial applications within Europe and globally.

If you want to learn more, please visit our website Industrial Grooved Piping Solution.