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FLANGE FOR PIPES/PIPING

WHAT IS A FLANGE?

A flange is a mechanical device to connect pipes, valves, pumps, and other equipment to form a piping system. It consists of a plate or ring that provides a mounting surface for attaching two sections of pipe or connecting a pipe to a valve, pump, or other device. Flanges are designed to be bolted together with a gasket between them to provide a tight, leak-proof seal.

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Flanges are widely used in various industries, including oil and gas, chemical processing, power generation, and water treatment, due to their ease of assembly and disassembly, which facilitates inspection, cleaning, and modifications to the piping system.

Flanges can be produced by casting or forging steel. In the oil and gas industry, forged steel flanges are preferred due to their intrinsic strength and durability.

FLANGE KEY PARAMETERS

When selecting (and ordering to suppliers) flanges for piping systems, several key measures and specifications must be considered to ensure compatibility with the system, proper fit, and reliable operation under the intended service conditions. These measures include diameter, pressure class, flange facing type, and material grade.

Here&#;s a breakdown of these critical flange specifications:

1. Flange Type and Specification

The first parameter to consider when ordering a flange is the shape/design: welding neck, slip-on, threaded, lap joint flange. The 13 types of standard/non-standard flanges are thoroughly described in this article.

Together with the type, the buyer shall indicate also the applicable specification, i.e. ASME B16.5, ASME B16.47, type A, EN -1, JIS, UNI, DIN, etc.

2. Nominal Pipe Size (NPS) and Diameter

• Nominal Pipe Size (NPS): Refers to the standardized size designation for pipes and the corresponding flanges. It&#;s not the actual dimension of the pipe or flange but a nominal specification that indicates compatibility.
• Outside Diameter (OD): The external diameter of the flange, which is larger than the OD of the pipe to accommodate bolting around the perimeter.
• Bore Diameter: The inner diameter of the flange that matches the inner diameter of the pipe, ensuring a smooth flow of the medium.

Note: for welding neck and socket-weld flanges, the pipe schedule shall also be communicated to the manufacturer/supplier. This is a piece of information that is typically missing in requests for proposals, tenders, or purchase orders but it&#;s necessary.

Refer to this article for more information about NPS.

3. Pressure Class (i.e. Flange Rating)

• Flanges are classified according to their maximum allowable pressure at a specific temperature. The pressure-temperature ratings are defined by ASME B16.5 for sizes up to 24 inches. Common classes include:
  • Class 150
  • Class 300
  • Class 600
  • Class 900
  • Class
  • Class
• The class designation determines the thickness of the flange and the size and number of bolting holes required to withstand the pressure.

4. Flange Facing Type & Flange Surface Finish

The flange face is the surface area that contacts the gasket. The type of flange facing affects the seal quality and is selected based on the fluid, pressure, and operational conditions. Common types include:

• Flat Face (FF): A flat surface that mates with another flat-faced flange, typically used for low-pressure applications.
• Raised Face (RF): Features a raised surface around the bore, which concentrates the gasket compression, making it suitable for a wide range of pressures.
• Ring Type Joint (RTJ): Designed for high-pressure/temperature applications, it uses a metal ring as a gasket seated in a grooved face.

According to the ASME B16.5 specification, the raised face is the standard facing for flanges (different facings, like RTJ or flat face FF, have to be ordered specifically).

The flange surface finish can be smooth, stock, concentric serrated, etc.

5. Material Grade

The material of the flange must be compatible with the piping system and the medium it will carry. Material choice impacts the flange&#;s strength, corrosion resistance, and suitability for specific temperatures and pressures. Common materials include:

• Carbon Steel: Widely used for its strength and versatility. (ASTM A105 is a common specification)
• Stainless Steel: Offers corrosion resistance for aggressive media. (e.g., ASTM A182 F304/304L, F316/316L)
• Alloy Steel: Used for special applications requiring high strength or resistance to heat and corrosion. (e.g., ASTM A182 F11, F22)

6. Cathodic Protection

Cathodic protection is a method used to prevent corrosion in metal structures by making them the cathode of an electrochemical cell. In the context of piping systems, flanges are critical points where corrosion can lead to leaks or failure, potentially causing safety hazards and operational issues. To mitigate this risk, especially in environments prone to causing corrosion, flange isolation kits are employed as part of a cathodic protection strategy. Learn more about the use of flange isolation kits to prevent corrosion and provide cathodic protection.

7. Other Technical Considerations

• Hub Design: Some flanges, like weld neck and slip-on, have different designs regarding their connection to the pipe (e.g., a long tapered hub for weld neck flanges).
• Gasket Surface: The surface finish of the flange face affects the seal quality and compatibility with different gasket materials.

Selecting the right flange involves a detailed understanding of these key measures and how they interact with the system&#;s design requirements, ensuring a secure, leak-proof connection that can withstand operational demands.

WHAT IS A FLANGED JOINT?

A flanged joint is a type of connection used in piping systems, equipment, and structural components that involves the use of flanges to mechanically join two sections. This joint is formed by bolting together a pair of flanges with a gasket between them to ensure a tight, leak-proof seal. Flanged joints are widely utilized across various industries&#;such as oil and gas, chemical processing, water treatment, and power generation&#;due to their reliability, ease of assembly and disassembly, and the ability to connect different types of components, such as pipes to valves, pumps, and tanks.

Flanged joints are used to connect pipes with other piping equipment (for example, another length of pipe, a valve, or a pressure vessel). Hundreds, even thousands, of flanged joints are necessary for a piping system to function.

A flanged joint comprises:

• Flanges: Flat, circular disks with bolt holes around the perimeter. The mating flanges (the &#;main&#; and the &#;companion&#; flange) are welded, screwed, or otherwise attached to the ends of pipes, valves, pumps, or other components. Flanges come in various types (weld neck, slip-on, blind, threaded, lap joint, and socket weld) to suit different applications and service conditions.

• Gasket: A sealing element placed between the flanges to prevent leaks. Gaskets are made from various materials, including rubber, graphite, PTFE, and metal, chosen based on the fluid properties, pressure, and temperature of the system.

• Bolts and Nuts: Used to bolt the flanges together, compressing the gasket to create a tight seal. The number, size, and material of the bolts and nuts depend on the flange specifications and the operating conditions.

Flanged joints are effective and economical ways to connect piping components, and feature the following characteristics:

• Leak-Proof Seal: When properly assembled, flanged joints provide a reliable seal that prevents the escape of liquids or gases, ensuring the safety and efficiency of the piping system.

• Ease of Assembly and Disassembly: Flanged joints can be easily bolted together or taken apart, facilitating quick installation, maintenance, repair, or modification of the piping system without the need for cutting or welding.

• Flexibility: Flanged joints accommodate slight misalignments and are suitable for both permanent and temporary connections, offering flexibility in system design and layout.

• Pressure and Temperature Tolerance: Designed to withstand the specific pressure and temperature conditions of the application, flanged joints are suitable for a wide range of operating environments.

Welded or Threaded Connections

A steel pipe can be welded on the flange (typical for weld neck, socket weld, slip-on, and lap joint flanges) or screwed into it (this is the case of threaded flange). Welded connections between pipes and flanges are used for high pressure and temperature applications, and diameters above 2 inches. Threaded connections are used for small-diameter piping systems that are not subject to mechanical forces such as expansion, vibration, contraction, or oscillation.

Insulation Kits

Flange insulation kits can also be used for flanged connections/joints, to protect the corrosion on flanges, bolts, and gaskets generated by the static currents running through the pipeline (this is called &#;cathodic protection&#;).

To prevent dangerous leakages in the pipeline, flanged joints shall be executed by trained personnel only (the standard TSE &#; TS EN Part 1-4, &#;Flanges and their joints&#; is the reference norm).

The image shows the elements of a flanged joint:

Welcome to the introductory guide on flanges integral components that help streamline assembly processes within complex industrial settings and large-scale machinery. If you are wondering &#; &#;What exactly makes a flange, a flange?&#; &#; we have your answer right here!

Think of a flange as a reinforcement component designed for connecting pipes, valves, pumps, and other machined parts. They operate in much the same way as the joints in our body, allowing the entire assembly to function correctly as fluids and gases move within.

Flanges can be manufactured in different styles and are used based on their requirements, whether they are industrial or cosmetic. They are typically joined to other pipe fittings with weld connections and sealed to other flanges with bolts and gaskets.

In short, flanges connect many things we use every day in the process industry, from utility water pipes to oil refinery equipment, to food processing assemblies, to pressure vessels, etc.

With this guide, we will embark on an in-depth exploration of flanges. These industrial components were designed in various specifications over decades, each serving an indispensable function.

Their roles extend across various industries, inducing invaluable contributions to various sectors that keep our economy functioning.

Understanding The Basics of Flanges

Gaining a comprehensive knowledge of the world of flanges might sound like a difficult undertaking, but they&#;re simple once you understand their purpose. Imagine building and installing a series of pipes to move fluids or gases from one location to another in multiple directions.

You generally can&#;t just weld pipes together and hope everything runs smoothly without supervision. Flanges are helpful when you want to keep pipes connected securely and avoid leaks within the system.

If you take the time to look at much of our infrastructure worldwide, you will typically find flanges if you know where to look. They keep pipes connected properly and allow them to stay in service for long periods of time.

Now, let&#;s discuss a few of the most used types of flanges!

Weld neck flanges are ideal for most high-pressure and/or high-temperature situations. Slip-on ones are capable of the same function in most cases but are often easier to install and ideal for non-critical jobs.

Blind flanges are required for most assemblies as they close off the end of a pipeline. Just like choosing the best tool for a job, you will usually want an engineer to sign off on the design! Safety is of course paramount, which is why the flanges we provide adhere to the latest ASME and ANSI standards.

In short, flanges keep liquids or gases moving safely. Next time you see a pipeline, you&#;ll know that flanges are those connectors that make it all work.

Understanding The Functions of Flanges: A Simple Explanation

Flanges connect pipes and help liquids or gases flow at the optimum rate, temperature, and pressure. Here are some functions of flanges:

Connect Pipes Securely

Flange connections join pipes together so that no liquid can leak. Whether in small rack plumbing or large industrial setups, flanges ensure lines stay connected reliably.

Help Distribute Pressure.

When liquids or gases flow through pipes, they exert pressure. Flanges help distribute this pressure evenly across the connected lines, preventing weak spots or bursts. Think of flanges as pressure managers that keep the system safe and efficient.  Especially true with orifice unions.

Helps With Inspection and Maintenance.

Flanges allow easy access to the connection point. This makes inspecting pipe assemblies and performing maintenance much easier. You can easily open a flange connection to check the pipes without dismantling the entire system or cutting into the pipe requiring rewelding.

Versatile

Flanges come in various shapes and sizes to fit different pipes and systems.

Absorb Vibrations.

Flanges function like cushions in systems where there might be volatility because of moving internal media or external ambient forces. They prevent shaking, keep things steady, and reduce the chances of operators nearby incurring any injury.

Handle Extreme Temperatures.

Some assemblies are designed to operate in extremely hot and cold environments. Flanges of various grades help keep pipes and fittings properly secured so that temperature changes do not damage them and prolong their overall service life.

Join Different Materials.

Sometimes, pipes made from different materials need to be connected. Flanges facilitate these connections seamlessly, allowing other materials to work together harmoniously.

Expansion and Contraction

Materials expand and contract with temperature changes and pressure differentials. Flanges accommodate these changes, preventing pipes from buckling or becoming misaligned.

Flanges form strong links, handle stress, are easier to maintain or replace and help systems work safely and competently. 

Basics of Flange Design

Flanges are indispensable components in integrating pipes, valves, and machinery across diverse industrial applications. These components take on the form of flat, circular discs punctuated by central apertures, facilitating the secure interconnection of pipes by bolting them together.

When engineers implement a flange into their preliminary design, they must first consider what material grade is ideal for their application.

Various materials (like mild carbon steel, stainless steel, or nickel alloys) have varying strength and corrosion resistance levels.

In addition to material grade considerations, the nominal size of the flanges in question is just as important to the pressure class to facilitate the proper flow and pressure requirement within an industrial assembly. 

Another key aspect is the type of sealing used between flanges. This prevents any leaks from occurring at the point of connection.

Gaskets, typically crafted from rubber, metal, or a combination of materials, help to ensure a strong seal. It is imperative to design a correct gasket groove in the flange for a good seal if a higher-pressure application is required.

Making solid and effective pipelines requires a standardized flange design. Things that must be considered before manufacturing flanges are the material grades.

How large the components should be (both the pipes and the fittings), and how to seal them properly. Preventing leakage in hazmat designs is of utmost importance.

Several Industries Which Use Flanges

Flange assemblies are ubiquitous across several industries. They make pipes, valves, and fitting equipment join properly for those specific industry requirements.

Oil and Gas Industry

When considering flanges, it&#;s likely the oil and gas industry comes to mind first, and for good reason. This truly needs no explanation &#; pipes, valves, fittings, and flanges&#; they are used in just about every application!

Chemical Industry

In the chemical processing world, flanges are a pipeline&#;s best friend. The proper sealing options and material grades are critical when processing highly corrosive fluids or gases. 

Clean Water Treatment Industry

Flanges help connect pipes that transport high volumes of water to treatment facilities and back out to be sent to our homes. Typically, these are larger-diameter flange applications.

Although volume is high, pressure and temperature are usually easier to work with.  These flanges are usually made to the American WaterWorks Association (AWWA) standards.

Power Plants

Flanges help pipes carry super-hot steam and water to generate electricity. In this and other industries, very precisely machined flange designs exist for additional components known as heat exchangers and the tube sheets that exist within their assemblies. 

Real Estate and Architecture

When companies design and construct buildings, they use flanges on pipes for heating, cooling, and plumbing within these structures. Flanges are also used in large infrastructure projects like bridges and tunnels to ensure liquids and gases are properly transported.

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Aeronautics

Material grade is of primary concern in the airline and space industry. In the highly volatile and vacuum environment well off the surface of our planet, we connect pipes in airplanes and spaceships to protect fuel and other media in a manner that requires several safeguards.

This is where the design requirements of ASME and ANSI can take a back seat to optimize for weight restrictions.

Manufacturing Industry

Steel fabrication work requires flanges to create pressure vessels and other machinery that form the backbone of specialized manufacturing and processing equipment.

Flange Prices in The Market

When we consider how much it costs to put an entire PVF job together, there are a few important things we need to think about.

The material composition, size, pressure-handling capacity, and manufacturing method &#; all of these elements impact both the price and the lead time of the required bill of materials.

Flange prices (as well as other steel fittings and components) are typically tied to the base costs of raw materials from steel mills and are subject to availability from said mills.

Bigger flanges naturally require more material to construct, which increases price in a non-linear fashion, given the labor required to manufacture.

Some flange materials (such as the higher nickel alloys) can handle lots of pressure, and that can really influence job costs.

The form of the steel is also to be considered, given that most flange designs prefer forgings, whereas many designs can accept plate or bar.

Remember, flanges and fittings need to work well and operate in sometimes hazardous environments. Quality is essential, and adhering to the latest industry and society standards is considered best practice.

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Different Types of Flanges For Various Applications

The various flange types may sound a bit too technical to a novice, but they&#;re essential in many industries, and understanding these styles is important. 

These are the team captains of the flange world. They have a slightly angled and extended neck, meant to be butt welded to the pipe, creating a reinforced and ideal connection for high-pressure environments.

They are frequently used in oil, gas, and chemical production, and are often required above other flange styles.

If easy installation is your thing, slip-on flanges are your friends. They slip over the pipe and get welded at the hub. They are frequently used in lower criticality applications.

Imagine the disc at the very end of a pipeline and you will likely think of a blind flange. They block off the end of a pipe assembly, which is super helpful when you want to clean, inspect, or close off a piping system, and have it rerouted before it hits that connection. 

They also can cap a line for pressure testing or cap the line where a system may be expanded in the future.

These flanges are the special design of the big six in the flange world. They are also known as Van Stone or rotating flanges, used to mate to stub ends for pipeline rotation designs.

Think of these as the companion connectors of the flange family, as that is typically what they are called. These flanges have threads on the inside (and sometimes outside), so you can easily screw them onto pipes and fittings.

People often use them for smaller pipe connections when they do not want to replace a male-threaded pipe in service.

These flanges have a socket with a counterbore for the pipe to fit into. They&#;re then welded around the base of the pipe, providing a strong connection. People often use them for small pipes that carry a moderate amount of pressure, where spacing is a constraint.

Simply put, these flanges are flat discs and are typically used for special applications where weight is a concern, or if the application is low/ambient pressure or temperature.

If precision is your game, orifice flanges are your ideal selection. They have a small opening design for instrumentation &#; measuring flow or for relief porting.

Flanges come in all shapes and sizes, each with their own benefits. Whether it&#;s holding up under extreme pressure, offering easy installation, or providing precision measurement, there&#;s a flange for every job.

Knowing about these different kinds can help you pick the right one, so your application works properly. The next time you encounter flanges in the industrial world, you&#;ll have a better understanding of what&#;s happening!

Different Types of Flange Face

When we connect pipes and equipment, flange face connections are important to consider. The flange facing is the bottom part of a flange that helps to form a good seal. There are different types of flange facings for several applications, as follows:

Raised Face (RF): This is the most common flange face. It has a raised/protruding portion of the steel body at the centerline. This basic design is utilized with other raised face flanges in which a spiral wound gasket is typically installed.

Flat Face (FF): This one is flat and often of mill finish. It&#;s for when you don&#;t need lots of pressure resistance &#; just a solid connection and likely with a rubber gasket.

Ring-Type Joint (RTJ): These flanges have a special groove for a ring-shaped gasket, which typically consists of metal as well. They are super strong connections and get used in high-pressure and high-temperature applications.

Tongue and Groove (T&G): These flange faces resemble puzzle pieces. They&#;re handy if you need to take things apart often.

Male-Female (M/F): These flanges are much like tongue and groove facings but of a slightly simpler design. They&#;re great when things have to line up just right.

Learning about different kinds of flange surfaces can assist you in choosing the correct one for your task. Selecting the right flange facing helps to prevent leakage.

As previously mentioned, this is extremely critical when operating with corrosive fluids and gases.

Flange

Classifications

and Service Ratings

Flange classifications group these types based on their production method and intended purpose. This enables us to select the correct flange for each job.

Service ratings are like grades for flanges. They tell us how much pressure and heat a flange can handle without getting damaged in service. It&#;s a bit like knowing how heavy a bag you can carry without it breaking.

The most common pressure classes of 150# through # are designed with the bulk of operating environments for all industries. The classes were originally designed to handle approximately the stated pressure in carbon steel at 750 deg. 

While we cannot publish the pressure-temperature charts in various materials we do have them all and can pass along information from the various specifications.

 Although the 150# is the most common (given how many jobs are relatively low-pressure applications) we offer all classes per the various ASME and ANSI standards, among many others. 

Flange Standards 

Standards for flanges set the baseline for industry performance of an entire pipeline assembly. These standards, such as ANSI, ASME, AWWA, API, and DIN, ensure things fit properly and are safely operated.

The United States often uses
ANSI, AMSE, AWWA, and API standards, while European folks commonly use DIN standards. Each design specification takes into consideration how big a flange should be, how much pressure it can handle, and how its sealing surface should function.

This makes it easy to install them where required, keep them in good condition, and repair or replace them if needed.

Understanding flange standards is crucial for various reasons. This simple guide has helped engineers and people curious about industries easily grasp the fundamental concepts of flange design and operation. For more information, please reach out to us!

Conclusion

Here at Texas Flange, we have been working with various flange designs, of all shapes and sizes and material grades, for decades. We made this guide to help you learn more about flanges, including how they work and the different styles that are available to you.

FAQs

Que: What are flanges primarily used for?

Flanges are connections (joints within an assembly) that tightly hold pipes, valves, and machinery together, ensuring nothing leaks and that the proper pressure and flow of the internal media is maintained during operation. They&#;re necessary for many jobs where people work with oil, gas, chemical processing, food processing, pressure vessels&#; You name it! 

Que: What are the different types of flanges?

The most common flanges in our industry are Weld Neck, Slip-On, and Blind. See the various other types in the earlier part of this guide for more information. Each style has special characteristics that work best for different jobs, based on their own requirements, like assemblies with high operating pressure, or simple constructs that require easy assembly, access, or removal.

Que: How do I choose the best flange for my project?

Selecting the appropriate flange involves considering pressure, temperature, and material compatibility. Get in touch with us here at Texas Flange so we can help you choose the best flange for your specific project!

Que: How do I know what size flanges to get?

You need to consider several factors while choosing the accurate size of flanges. Firstly, you should identify the pipe size or equipment to which the flange will connect. Flange size is typically specified based on the nominal pipe size or equipment dimensions.

Furthermore, keep yourself updated about the pressure and temperature of your industrial application. The pressure and temperature of the application impact the flange rating and material. Consulting engineering standards such as ASME B16.5 or ASME B16.47 can help you select the correct flange size for your specific needs.

Que: What are the basics of flanges?

Flanges are an integral component in various industrial applications. They connect pipes, vessels, valves, and other machinery equipment. They are available in various sizes, shapes, and even materials.

They are famous for joining pipes and building unbreakable bonds, which lead to the smooth and efficient flow of liquid and gases through the pipes. Also, They play a crucial role in sealing and joining different system components, providing ease of maintenance and repair.

Que: What happens if you use a flange that&#;s too big? 

If you&#;re using a too big flange, it can lead to several issues&#;for instance, improper alignment of connected components. Improper alignment leads to leakage and loss of system integrity. Also, it can strain the connected pipes and equipment, potentially leading to structural damage or failure. 

A large flange may be more challenging to install and maintain, requiring more work and money. Choosing flanges that correspond to the pipe size and system requirements is critical to prevent these issues.

Que: How do you specify a flange?

Key specifications include:

• Flange Type: Choose the appropriate flange type (e.g., slip-on, weld neck, or socket weld) based on the application and connection method.

• Size: Specify the flange size according to the nominal pipe size or equipment dimensions.

• Pressure Rating: Determine the required pressure rating, often expressed in pounds per square inch (PSI) or bar, based on the system&#;s operating pressure.

• Additionally, you must specify the flange material (carbon steel, stainless steel, or alloy steel and facing type (e.g., raised face or flat face)

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