What Are The Most Common Flange Types?

This blog post will cover The Most Common Flange types used in today’s industrial applications. Flanges are essential components in industrial applications. Even though there are many different types of flanges, they all share a common goal- to connect piping systems together. Let’s explore the specifics of the seven most popular flange types, their unique characteristics, and their practical uses that make them essential in various industries.

If you are looking for more details, kindly visit MIDAS.

AWWA, ANSI, DIN, 1/2″-thick, Plate, Backing, and Exhaust Flanges

Weld Neck Flange:

Weld neck flanges perform exceptionally well in high-pressure systems. They are one of the most common flange types. Their long neck allows a seamless butt weld directly onto the pipe, leaving a smooth connection. Because of this, they are perfect for use in sectors like the oil and gas industry, where dependability under high pressure is crucial. This style of flange connection is almost exclusively used in larger diameters and higher-pressure classifications.

Slip-on Flange:

The simplicity of installing slip-on flanges makes them popular among manufacturers and fabricators. Because the slip-on flange lacks a weld bevel and permits pipe length adjustment in relation to flange location, it is an easy and excellent substitute for a weld neck. The matching pipe will have plenty of room in the slip-on’s bore. This extra room provides sufficient workspace for the fabricator and welder to connect. They are frequently used in sectors like shipbuilding and construction that demand quick and effective setup. This kind of flange is widely used in applications with lower pressure. A hub found on most slip-on style flanges frequently resembles a raised face in terms of dimensions. In cases where space is restricted, and the application permits a “ring style” slip-on, it can be outfitted without a hub. A ring-style slip-on without a hub still qualifies as a slip-on flange and can be recognized as you see fit, even if the hub style is more frequently used when discussing slip-ons. Higher-pressure class slip-ons are commonly designed with a lap joint height for improved attachment.

Socket-weld Flange:

Socket-weld flanges are resilient to high pressure and temperatures, benefiting the power generation and chemical processing industries. With a counterbore in the middle to enable a clean pipe weld into the socket, socket weld flanges are less popular but no less effective connection for flanges that require less total available space than a typical weld neck flange. These are typically supplied in smaller nominal pipe sizes, and when needed, they’re an excellent substitute for slip-on and weld necks. If the fluid is not corrosive and the pressure class is relatively low, a socket weld may be chosen for an assembly with limited space or extremely high-temperature duty.

Threaded Flange:

Threaded flanges are easy to install and perform well in low-pressure applications. They are a vital component in piping systems and other environments where it’s essential to maintain a tight seal without doing a lot of welding. Threaded flanges have a female NPT thread in the middle for connecting to male NPT threaded piping. They are also sometimes called companion flanges, screw flanges, or NPT flanges. Threaded flanges are frequently used to create reduced connections. In addition to the basic NPT form, as defined by the ASME B16.5 specification, several thread styles can be machined.

Blind Flange: 

Blind flanges are essential for closing off portions of a pipe system. Blind flanges are dependable barriers in petrochemical and other hazardous material-related industries, guaranteeing worker safety and stopping leaks during emergencies or maintenance. Blind flanges with raised faces frequently have a slight indentation in the middle, as seen in B16.1 and other industry standard cast steel requirements from decades ago. This recess allowed the pipe end to mate with the connecting flange and for a seal to form between the blind and the connecting flange. To produce a dished head formation at the top of the flange, the more oversized OD blind flanges have a concave recess through the blind’s body. For the most part, blind flanges won’t be produced in these forms because the earlier cast iron specification is somewhat outdated. Instead, go for a modern blind flange with or without a hub.

Lap Joint Flange:

A Lap joint flange makes the list among the other common flange types. They are also known as Backup flanges, Loose Ring flanges, Loose Hubbed flanges, and Van Stone flanges. Easily disassembled, lap joint flanges offer flexibility and are perfect for industries like the food and beverage industry that need regular maintenance or adjustments. The hubs can be adjusted to your specifications and are usually taller than a slip-on design. Higher-pressure class slip-ons are frequently designed with a lap joint height for improved attachment. Customers will occasionally choose a slip-on intended to resemble a lap joint with a machined hub if the hub height is not an issue and a lap joint is not easily accessible. Industrial flanges are used in various industries, such as structural applications and plumbing. Rolled angle rings and lap joint flanges are two parts that are essential to many processes. The main distinction between rolling angle rings and lap joint flanges is that the latter is exclusively offered in a butt-weld arrangement. Conversely, lap joint flanges are available in slip-on and butt-weld varieties. The backing flange on a lap joint flange can rotate, unlike the backing flange on a rolled angle ring.

Custom Flange:

Contrary to the name, custom flanges are common flange types with many applications and uses across various industries. Our machine shop makes it possible to use AIS and import materials to build products that satisfy various specifications. We also facilitate quick changes to our stock of goods to serve our customers better. Whether you need to reverse engineer a sample or a CAD drawing, we can work with you on prototypes, production quantity manufacturing, and even product warehousing.

API’s Machining Capabilities:

Machining inner diameter, outer diameter, gasket face, chamfers, and tapers up to 120″ outer diameter

Single point threading of inner and outer diameter with standard or metric pitch

Straight turning, tapers, and angles of inner and outer diameter face

Profile milling, facing, contouring, pocketing, boring and threading

Milling straight and tapered pipe threads

Single-part or large production orders

Bolt-hole drilling up to 3″ diameter

Turning shafts up to 60″ in length

Steel, Aluminum, Duplex, Super Duplex, Alloy 20, and other exotic metals

Each flange type has a unique role to play. At API International, Inc., we pride ourselves on offering a diverse range of fittings, including these essential flange types, to meet the specific needs of various industries. Contact our sales team if you have questions or need a quote. Our dedicated sales team staff are ready to help you find the industrial fittings you need for your project.

Types of Flanges

Flange types As already described before, the most used flange types ASME B16.5 are: Welding Neck, Slip On, Socket Weld, Lap Joint, Threaded and Blind flange. Below you will find a short description and definition of each type, completed with an detailed image.

MOST COMMON FLANGE TYPES

Welding Neck flange

Welding Neck Flanges are easy to recognize at the long tapered hub, that goes gradually over to the wall thickness from a pipe or fitting.

The long tapered hub provides an important reinforcement for use in several applications involving high pressure, sub-zero and / or elevated temperatures. The smooth transition from flange thickness to pipe or fitting wall thickness effected by the taper is extremely beneficial, under conditions of repeated bending, caused by line expansion or other variable forces.

These flanges are bored to match the inside diameter of the mating pipe or fitting so there will be no restriction of product flow. This prevents turbulence at the joint and reduces erosion. They also provide excellent stress distribution through the tapered hub and are easily radiographed for flaw detection. This flange type will be welded to a pipe or fitting with a single full penetration, V weld (Buttweld).

DETAILS OF WELDING NECK FLANGE

Details of Welding Neck flange

Weld Neck flange

Butt Weld

Pipe or Fitting

Slip On flange

The calculated strength from a Slip On flange under internal pressure is of the order of two-thirds that of Welding Neck flanges, and their life under fatigue is about one-third that of the latter.

The connection with the pipe is done with 2 fillet welds, as well at the outside as also at the inside of the flange. The X measure on the image, are approximately:

Wall thickness of pipe + 3 mm.

This space is necessary, to do not damage the flange face, during the welding process.

A disadvantage of the flange is, that principle always firstly a pipe must be welded and then just a fitting. A combination of flange and elbow or flange and tee is not possible, because named fittings have not a straight end, that complete slid in the Slip On flange.

DETAILS OF SLIP ON FLANGE

Details of Slip On flange

Slip On flange

Filled weld outside

Filled weld inside

Pipe

Socket Weld flange

Socket Weld flanges were initially developed for use on small-size high pressure piping. Their static strength is equal to Slip On flanges, but their fatigue strength 50% greater than double-welded Slip On flanges.

The connection with the pipe is done with 1 fillet weld, at the outside of the flange. But before welding, a space must be created between flange or fitting and pipe. ASME B31.1 127.3 Preparation for Welding (E) Socket Weld Assembly says:

In assembly of the joint before welding, the pipe or tube shall be inserted into the socket to the maximum depth and then withdrawn approximately 1/16″ (1.6 mm) away from contact between the end of the pipe and e shoulder of the socket.

The purpose for the bottoming clearance in a Socket Weld is usually to reduce the residual stress at the root of the weld that could occur during solidification of the weld metal. The image shows you the X measure for the expansion gap.

The disadvantage of this flange is right the gap, that must be made. By corrosive products, and mainly in stainless steel pipe systems, the crack between pipe and flange can give corrosion problems. In some processes this flange is also not allowed. I am not an expert in this matter, but on the internet, you will find a lot of information about forms of corrosion.

Also for this flange counts, that principle always firstly a pipe must be welded and then just a fitting.

DETAILS OF SOCKET WELD FLANGE

Details of Socket Weld Flange

Socket Weld flange

Filled weld

Pipe X = Expansion gap

Lap Joint flange

Lap Joint Flanges have all the same common dimensions as any other flange named on this page however it does not have a raised face, they used in conjunction with a “Lap Joint Stub End”.

These flanges are nearly identical to a Slip On flange with the exception of a radius at the intersection of the flange face and the bore to accommodate the flanged portion of the Stub End.

Their pressure-holding ability is little, if any, better than that of Slip On flanges and the fatigue life for the assembly is only one tenth that of Welding Neck flanges.

They may be used at all pressures and are available in a full size range. These flanges slip over the pipe, and are not welded or otherwise fastened to it. Bolting pressure is transmitted to the gasket by the pressure of the flange against the back of the pipe lap (Stub End).

Lap Joint flanges have certain special advantages

Freedom to swivel around the pipe facilitates the lining up of opposing flange bolt holes.

Lack of contact with the fluid in the pipe often permits the use of inexpensive carbon steel flanges with corrosion resistant pipe.

In systems which erode or corrode quickly, the flanges may be salvaged for re-use.

DETAILS OF SOCKET WELD FLANGE

DETAILS OF LAP JOINT FLANGE

Lap Joint flange

Stub End

Butt weld

Pipe or Fitting

Stub End

A Stub End always will be used with a Lap Joint flange, as a backing flange.

This flange connections are applied, in low-pressure and non critical applications, and is a cheap method of flanging.

In a stainless steel pipe system, for example, a carbon steel flange can be applied, because they are not come in contact with the product in the pipe.

Stub Ends are available in almost all pipe diameters. Dimensions and dimensional tolerances are defined in the ASME B.16.9 standard. Light-weight corrosion resistant Stub Ends (fittings) are defined in MSS SP43.

Details of Lap Joint Flange LAP JOINT FLANGE WITH A STUB END

Threaded flange

Threaded Flanges are used for special circumstances with their main advantage being that they can be attached to the pipe without welding. Sometimes a seal weld is also used in conjunction with the threaded connection.

Although still available in most sizes and pressure ratings, screwed fittings today are used almost exclusively in smaller pipe sizes.

A threaded flange or fitting is not suitable for a pipe system with thin wall thickness, because cutting thread on a pipe is not possible. Thus, thicker wall thickness must be chosen…what is thicker ?

ASME B31.3 Piping Guide says: Where steel pipe is threaded and used for steam service above 250 psi or for water service above 100 psi with water temperatures above 220° F, the pipe shall be seamless and have a thickness at least equal to schedule 80 of ASME B36.10.

DETAILS OF THREADED FLANGE

Details of Threaded flange

Threaded flange

Thread

Pipe or Fitting

Blind flange

Blind Flanges are manufactured without a bore and used to blank off the ends of piping, Valves and pressure vessel openings.

From the standpoint of internal pressure and bolt loading, blind flanges, particularly in the larger sizes, are the most highly stressed flange types.

However, most of these stresses are bending types near the center, and since there is no standard inside diameter, these flanges are suitable for higher pressure temperature applications.

DETAILS OF BLIND FLANGE

Details of Blind flange

Blind flange

Stud Bolt

Gasket

Other flange

REMARK(S) OF THE AUTHOR...

A SIMPLE MANNER TO MAKE A 1/16" GAP...

Have you ever seen a Socket Weld contraction ring ?. It is a split ring that is engineered and designed to give a pre-measured 1/16″ minimum gap for socket welds. Made from a certified stainless steel, and resists corrosion from chemicals, radioactive materials and water. Once inserted into the fitting the ring becomes a permanent part of the joint. It will not rattle or vibrate even under extreme pressure. Another manner is the applying of in water-soluble board. Make rings with a hole punch with outside and inside diameter of the pipe. Insert the ring into the flange or fitting and after hydrotesting there is no ring anymore. For both solutions, ask your customer for permission.

HOLD THEM ON ITS PLACE...

If a Lap Joint flanged connection must be disassembled, for example to replace a gasket, it is not always possible to do that on the conventional manner. The conventional manner is the use of a flange spreader or crowbar that pushed off the two flanges. By Lap Joint flanges that is not possible, because these slide back over the pipe, while the Stub Ends stay together. To prevent that, often are on 3 places, single millimeters behind the flange, on the Stub End, short pieces flat steel, will be welded. There is no general rule how a Lap Joint flange must be hold on its place, and therefore it can deviate per customer specification.

YOU KNEW THAT...?

At the smallest sizes, the amount of wall lost during threading actually equals approximately 55% of the original pipe wall.

BUTT WELDS VS FILLET WELDS

In systems with relatively high pressures and temperatures, we need to avoid the use of fillet welds. Butt welds, in such systems must be used. The strength of a butt weld is at least the strength of the base material. The strength of fillet welds related to the strength of the butt weld, is about one third. At higher pressures and temperatures, the expansion and contraction caused fast for serious cracks in fillet welds and therefore the use of butt welds is essential. For conduits to critical machinery such as pumps, compressors and turbines, which are exposed to vibration (in addition to the expansion and contraction), we should avoid the use of fillet welds or threaded connections. Fillet welds have a higher sensitivity to cracks due to stress concentration, while butt welds are characterized by smooth exchange of tensions. So, for critical situations, we have to use flanges connected by butt welding like as weld neck and ring type joint, and avoid using flanges connected by fillet welds like Slip On or Socket Weld.

10 Most Used Types of Pipe Flanges: Their Features, Uses, and Advantages in Piping

Piping flanges are key elements of a piping system and are used in various industries, such as oil and gas, petrochemical, manufacturing, etc. These flanges connect pipes to valves or equipment or with another pipe spool and form a tight seal that prevents leaks and ensures efficient fluid flow within the system.

Several types of piping flanges are available, each with unique features and benefits. You must understand the differences between these flanges to choose The Right one for a particular application. In this article, I have listed the different types of piping flanges, their function, and applications in various piping systems. The following types of flanges are covered.

The pipe flanges are the second most used joining method after welding. They are used when joints need dismantling. It provides flexibility for maintenance. Flange Connects the pipe with various equipment and valves. Breakup flanges are added to the pipeline system if regular maintenance is required during plant operation.

A flanged joint comprises three components; flanges, gaskets, and bolting, and is assembled by a pipefitter. Special controls are required to select and apply all these elements to attain a joint with acceptable leak tightness.

Related Questions

Q- What’s in a flange?

A- Flange is a type of piping component that is used to join pipe to pipe, or other piping components and equipment/ Flange consists of three components: metallic flange, which is welded or bolted with pipe or other equipment. The second is a gasket that seats between two flanges, and the third is the bolting material that keeps the connecting flanges together to create a secure and leak-proof connection.

Q- What is a flange used for?

A-Flanges are commonly used in piping systems, allowing for easy disassembly and maintenance of the system. They are also used in industrial equipment such as pumps, valves, and static equipment to connect them with piping systems.

Q-

What are flange types?

A-

Depending on the

application and the requirements of the piping system or equipment, several types of flanges are used in piping. Such as weld neck, threaded, socket, etc.; refer to this article to learn about 10 main types. 

Q-

What are the 3 most common flange types?

A- Weldneck, Socket weld and Threaded are the most commonly used types of flanges in piping systems.

Q-

What are the examples of flanges?

A- Weld neck, slip-on, socket weld, threaded, blind flange, and lap joint type flanges are some of the commonly used flnages. 

However, using a flange connection in underground piping is not advisable when it is supposed to be buried. The flange is also the most common source of leaks and fires in a process plant. There are a variety of flanges available to suit the requirements. A flange can be classified in several alternate ways based on the following:

Types of Connection

Flange facing Types

Pressure-Temperature Ratings

Material Types

Threaded Flanges

A threaded Flange is also known as a screwed flange, and it has a thread inside the flange bore, which fits on the pipe with a matching male thread on the pipe. This type of joint connection is speedy and simple but unsuitable for high pressure and temperature applications. Threaded Flanges are mostly used in utility services such as air and water.

Threaded Flange is mostly used in utility services such as air and water

It is not suitable for high presser and temperature applications

It is also available in limited Size of NPS 4” and below

Threaded Flanges can be FF or RF

It is a low-cost flange. 

Threaded Flange

Related Questions

Q- What is a threaded flange?

A- A threaded flange is a type of flange that has threads on the inside bore, which allow it to be screwed onto a pipe or fitting.

Q- Where is threaded flange used?

A- Threaded flanges are commonly used in low-pressure applications where frequent disassembly may be required, such as plumbing, HVAC, and water treatment.

Socket-Weld Flanges

Socket-Weld Flanges have a female socket in which the pipe is fitted. Fillet welding is done from outside on the pipe. Generally, it is used in small bore piping and is only suitable for low pressure and temperature application.

Socket-Welded Flanges can be FF or RF.

The cost of flange and fabrication is moderate.

Socket Weld Flange socket weld flange cross-section with weld detail

Related Questions

Q- What is a socket weld flange?

A- A socket weld flange is a type of flange with a socket or bore designed to fit over the end of a pipe and is then welded on the pipe, as shown in the image above. 

Q- What is the socket flange used for?

A- The socket weld flange is commonly used in smaller size piping systems with low temperature and pressure applications.

Q- What is the difference between socket weld flange and slip on flange?

A- The main difference between a socket weld flange and a slip-on flange is the installation method. Socket weld flange require welding only on the outside of the joint as shown in the image above. Whereas, Slip on flange require welding on both the inside and outside of the joint as shown in the image below. 

Q- What is the difference between a socket weld and a Buttweld flange (Weld neck flange)?

A- A socket weld flange and a butt weld flange are two different types of flanges that are used for different purposes.

A socket weld flange is a type of flange with a socket or bore designed to fit over the end of a pipe, and is then welded outside of the pipe with fillet-type welding. The socket weld flange is typically used in smaller size and Low-pressure temperature piping systems.

On the other hand, butt weld flange is a type of flange that is designed to be welded directly to the beveled end of the pipe, and it is used for high-pressure temperature applications in oil and gas, chemical processing, and power generation. 

Flange and Olet Quiz – Test yourself, Take This Quiz

 Slip-On Flanges

Slip-On flange has a hole with a matching outside diameter of pipe from which pipe can pass. The flange is placed on pipe and fillet welded from both inside and outside. Slip-On Flange is suitable for low pressure and temperature application.

This type of flange is available in large sizes also.

For more All Flanged Crossinformation, please contact us. We will provide professional answers.

It can be FF or RF

The cost of flange and fabrication is moderate.

Slipon Flange Slipon raised face (SORF) flange cross-section with weld detail

Related Questions

Q- What is slip on flanges?

A- A slip-on flange is a type of flange that is designed to slip over the end of a pipe or fitting and then be welded both inside and outside, as shown in the image above. Slip-on flanges have a slightly larger diameter than the pipe or fitting to which they are attached, allowing them to slip over the end of the pipe or fitting. 

Q- What is the difference between slip on and weld neck flange?

A- The main difference between slip on and weld neck flange is how they are welded with the pipe. Slip on flange is fillet welded, whereas weld neck flange is butt welded with pipe. Slip-on flanges are commonly used in low-pressure applications where the welded joint is not subject to high stresses.  Weld neck flanges are commonly used in high-pressure and high-temperature applications, where the joint is subject to high stresses.

Lap Joint Flanges

The lap flange has two components: a stub end and a loose backing flange. The stub end is butt-welded to the pipe, and the backing flange freely moves over the pipe. The backing flange can be of a different material than stub material and normally of carbon steel to save the cost. A lap flange is used where frequent dismantling is required, and space is constrained.

The backing flange can be of a different material than stub material and normally of carbon steel to save the cost.

This flange provides better joining due to butt-weld as compared to socket and threaded type flanges.

Not suitable for small size, Costly components, and fabrication as compared to threaded, slip-on, and socket flange.

The lap flange provides connection flexibility as you can freely rotate the flange on the pipe. It is used where frequent dismantling is required and space is constrained.  

Lap Flange with stub and hub Lap Flange cross-section with weld detail

Related Questions

Q- What is lap joint flange?

A- A lap joint flange comprises two main parts: a stub end and a loose backing flange. The stub end is welded directly to the pipe, while the backing flange slides over the pipe and is not attached to it. The backing flange can be made of a different material than the stub end, and is often made of lower cost carbon steel.

Lap joint flanges are particularly useful in situations where the piping system needs to be frequently dismantled and reassembled. This is because the backing flange can be easily removed and reattached without removing the entire flange assembly. It is also used in piping systems where space is limited and a compact flange design is required.

Q- What is the difference between lap joint flange and slip on flange?

A- Lap flange consists of two parts: stub end and backing flange. In a lap joint flange, stub end is directly welded to the pipe by butt welding, while a slip-on flange is welded on the pipe by a fillet weld from inside and outside.  

Q- What are two advantages of a lap joint flange?

A- The main two advantages of using a lap joint flange are listed below. 

Easy disassembly and maintenance: One advantage of lap joint flanges is that they are easy to dismantle and reassemble when maintenance or fast joining is required. The loose backing flange can be easily aligned with another flange, allowing the piping system to be easily disassembled and reassembled.

Flexibility in material selection: Another advantage of lap joint flanges is that they allow for flexibility in material selection. The stub end can be made from a different material than the backing flange, which can be beneficial in situations where the material properties of the two components need to be different. For example, a stub end can be made of a corrosion-resistant material, with the backing flange made from a cheaper material, as it will never come in contact with a fluid.

Weld Neck Flanges

Weld neck flange is the most widely used type in process piping. It gives the highest level of joint integrity as it is butt-welded with a pipe. These types of flanges are used in high pressure and temperature application. Weld neck flanges are Bulky & costly with respect to other types of flanges.

High skill is required for fabrication.

Required more space to accommodate in the piping system due to the long hub

Weld Neck Flange is available in all sizes & it can be FF, RF, or RTJ type

You can see the Weld Neck flange welded with pipe

Related Questions

Q- What is the purpose of a weld neck flange?

A- The purpose of a weld neck flange is to provide a strong and secure connection between two joints (Pipe to pipe or pipes to valve, equipment, etc.). It has a long tapered neck (which is called a hub) that is welded that provides a smooth transition of the flow. Weld neck flanges are commonly used in high-pressure and high-temperature applications.

Q- What is the standard weld neck flange?

A- Flanges manufactured following the standards such as ASME B16.5, ASME B16.47, DIN, or other similar are called standard weld neck flanges. 

Q – What are the parts of a weld neck flange?

A – Weld neck flange typically consists of three main parts:

Flange body: This is the main part of the flange that connects to other flanges. It has a circular shape with bolt holes around the perimeter for attaching the flange.

Tapered neck or hub: This flange portion is welded to the piping components or equipment. The tapered neck or hub extends from the flange body and gradually narrows down to the diameter of the pipe.

Flange face: This is the surface of the flange that comes into contact with the gasket. Depending on the requirements, the flange face may be raised, RTJ, or flat.

Q- What are the different types of weld flanges?

A – Depending on the flange face, it can be a flat face, raised face, or RTJ type. Refer to the Flange Face section for more information. 

Blind Flanges

The blind flange is a blank disc with a bolt hole. These flanges are used with another type of flange to isolate the piping system or terminate the piping as an end. Blind flanges are also used as a manhole cover in the vessel.

Related Questions

Q-What is a blind flange?

A- Blind flange is a type of flange that is used to close off the end of a pipe or vessel. It is called a “blind” flange because it has no opening for fluid or gas to flow. 

Q- Why use a blind flange?

A- Blind flanges are commonly used in piping systems where future connections may be needed or where the end of the line needs to be sealed off. They are also used in equipment to close off nozzle openings when not in use.

Q- How many types of blind flanges are there?

A- Blind Flabges are available in mainly three face types. Flat face, raised face, or RTJ type. 
Q- What is the difference between a Blind flange and a Blank flange or Blind?
A- The terms “blind flange” and “blank flange” are sometimes used interchangeably, but they can refer to different types of flanges depending on the context.

As said earlier, a blind flange is a type of flange that is used to close off the end of a pipe or vessel nozzle. On the other hand, a blank (or it is called a blank flange by some) is used to isolate part of the piping system for short-term maintenance activities. Refer to the image given here for easy understanding.

Reducing Flange

A reducing flange is used in place of a standard flange to allow for a change in pipe size. This flange eliminates the need for a standard reducer in piping.  The flange consists of one specified diameter with a smaller diameter bore size.

Except for the bore and hub dimensions, a reducing flange has dimensions of the standard pipe flange size and is considered economical to make a pipe size transition.

These flanges are available in weld neck, slip-on, and threaded end types. Reducing flanges are an economical way to make transitions between pipes of different sizes, however, due to high-pressure loss, they are rarely used in piping. ASME B16.5 covers the dimensions of reducing flanges.

Image source: www.msmmfg.com

Related Questions

Q- What is reducing flange?

A- Reducing flange is a type of flange that is designed to connect pipes or fittings of different sizes. It is similar in design to a regular flange but has a smaller diameter on connecting end, as shown in the image above.

Expander Flange

It is similar to a weld neck flange but increases the size of the pipe to the first or second larger size. It is an alternative to using a reducer and weld neck flange. Useful for connecting to valves, compressors, and pumps.

These flanges are specially designed. Dimensions of the weld neck are in line with the connecting pipe, other dimensions are in accord with standard ASME B16.5 flanges.

Expander flange

Image source: www.msmmfg.com

Flangeolet / Weldoflange / Nippoflange

Flangeolet is a combination of two olets (mainly weldolet or nipple) and a flange as you can see in the image that the hub length is longer, like a long neck weld flange. It is a 90 Degree branch connection used for high-pressure piping.

It reduces the two weld joints more than the traditional Olet + Pipe + Flange connection and one weld joint in the case of the Olet + Flange connection. You can see the image of the flangeolet branch.

Flange Types Based on Faces Type

Depending on the flange facing Types, it can be further classified as

Flat Face (FF)

Raised Face (RF)

Ring Joint (RTJ)

Tongue and groove (T&G)

And Male and Female type

Types of Flange Faces

Flat Face

As the name suggests, the flat face flange has a flat face. Flat face flanges are used when the counter-flanges are flat faces. This condition occurs mainly in connection to Cast Iron equipment, valves, and specialties. A full-face gasket is used when a flat face flange is used.

Raised Face

Raised face flange has a small portion around the bore raised from the face. The gasket seat on this raised face. The height of the raised face depends on the flange pressure-temperature rating, known as a flange class. For 150# & 300# height of the raised face is 1/16”, and above 300#, it is 1/4”. The inside bore circle type of gasket is used with a raised face flange.

RTJ Face

Ring joint type face flange has a specially designed grove in which metal gasket seats. This type of flange is used in high pressure and temperature services.

RTJ, Raised and flat face

Related Questions

Q- What is the difference between RF and FF?

A- RF is raised face, and FF is Flate Face. The main difference between RF and FF flanges is the shape of the sealing surface, as shown in the image above. RF flanges have a raised face, while FF flanges have a flat face. 

Q- What does RF and FF mean in flange?

A- RF means “Raised Face” and FF means “Flat Face” 

Q-Can you mate / connect RF and FF flanges?

A- No, it is not good practice to connect RF and FF flanges. 

Q-What is difference between RF and RTJ flanges?

A- RF and RTJ are two different types of flange faces, as shown in the image above. RTJ flange has a grove on the face in which metallic ring gasket seats.
Q-What does RTJ flange stand for?

A- RTJ stands for Ring Type Joint Gasket flange.

Flange Materials

Flanges are welded to pipe and equipment nozzle. Accordingly, it is manufactured from the following materials;

Carbon steel

Low alloy steel

Stainless steel

Combination of Exotic materials (Stub) and other backing materials

The list of materials used in manufacturing is covered in ASME B16.5 & B16.47.

ASME B16.5 -Pipe Flanges and Flanged Fittings NPS ½” to 24”

ASME B16.47 -Large Diameter Steel Flanges NPS 26” to 60”

Commonly used Forged material grads are

Carbon Steel: – ASTM A105, ASTM A350 LF1/2, ASTM A181

Alloy Steel: – ASTM A182F1 /F2 /F5 /F7 /F9 /F11 /F12 /F22

Stainless Steel: – ASTM A182F6 /F304 /F304L /F316 /F316L/ F321/F347/F348

Related Questions

Q- What is ASME B16.5?

A- ASME B16.5 is a standard for Pipe Flanges and Flanged Fittings for sizes NPS ½” to 24”. Don’t get confused between ASTM and ASME. These two are different standards. There is no ASTM B16.5. 

Flange Inspection

Before dispatching from the manufacturer, each flange is inspected to ensure quality. During an inspection, you have to check the following;

Outer & Inner Diameter of body

Bolt Circle & Bolt hole Diameter

Hub Diameter & thickness of weld end

Length of the Hub

Straightness and alignment of the bolt hole

ASME B16.5 and B16.47 standards cover permissible tolerances for inspection.

Flange Inspection

Marking on the Flange Body

Each piping component is marked for proper identification. Marking of flanges must include the following so that during fabrication and post-fabrication, it can be easily traced;

Manufacturer logo

ASTM material code

Material Grade

Service rating (Pressure-temperature Class))

Size

Thickness (Schedule)

Heat No

Special marking if any QT (Quenched and tempered) or W (Repair by welding)

Flange Marking

The Major Advantages of Flanges and Flange Fittings

Hydraulic connections mate pipes, hoses or tubes together or to components such as cylinders, pumps, valves or ports in other equipment. They are used in to complete a leak free hydraulic fluid system. These components combine to ensure the system is free of leaks or other failure under high pressures. Because of certain connection configurations and applications, flange fittings or separate flanges are the best or sometimes only practical solution to make an efficient and leak free connection.

Flange connections are typically used in applications that will encounter exceptionally high pressures when using pipe or tubing with an OD over 7/8 inches. They may be

bolted together to mate two sections of pipe (tube or hose), or bolted or screwed into the component to secure a flange fitting or section of pipe. Flanges can also be disassembled for easy access to modify the system, clean or inspect it. Certain flanges may also be permanently welded together or to the port section of the component (motor housing, valve port, etc.). More commonly, a flanged joint is made by bolting two flanges together with a gasket in-between to ensure a secure seal.

There are two primary types of flanges:

• SAE Code 61 flanges are used for applications requiring working pressure of 3,000 to 5,000 PSI
• SAE Code 62 flanges are used for applications requiring working pressure of up to 6,000 PSI

The hydraulic flange standard is ISO , which includes SAE Code 61 and 62 or SAE J518 UNC thread North American Standard, along with International standards with metric threads.

NOT Interchangeable

It is important to note that the two flange style codes (61 and 62) are not interchangeable due to their pressure ranges and their different bolt patterns.

As shown in this diagram of overlapping code 61 and code 62 4-bolt flanges the dimensional placement of holes are close, but not identical. Note the difference in the bolt-hole’s center-to
-center dimensions.

As shown in the flange diagram and chart below,  the distance 

between hole centers for dimension A in a 2 inch Code 61 versus a Code 62 flange varies by as little as 0.062 inches and for dimension B is offset by a significant 0.75 inches.

There is also another style that must be accounted for and not interchanged with Code 61 or 62 flanges. This other 4 bolt flange often found in the field is made for Caterpillar equipment and called (not surprisingly) a Caterpillar flange. This style is almost an exact match to the SAE Code 62 4-bolt flange with one major difference:

The flange head on an SAE Code 62 has a thickness which ranges from 0.305 inches on the 1⁄2 inch flange to 0.495 inches on the 2 inch flange, where the Caterpillar flange head thickness is 0.560 inches for all 4-bolt flanges. Hence an important distinction as to why they should not be interchanged.

Although many SAE 4-bolt hydraulic flanges might look alike or that different flanges and fittings might appear to be compatible, that is usually not the case. SAE Code 61, SAE Code 62 and Caterpillar 4-bolt flanges have dimensional variations and slight differences in configuration, plus the differences in allowable working pressure, do not allow them to be used together or interchanged. Take the example from on the The Fluid Power Safety InstituteTM website:

A diesel mechanic was installing a new hydraulic motor onto a machine. While reconnecting the hydraulic hose he inadvertently used a 4-bolt split flange that did not line up with the holes on the motor housing. Suspecting the holes in the motor were not tapped in the proper place he filed the holes in an attempt to have them line up with the flange. He essentially modified a 6,000 PSI SAE Code 62 4-bolt flange to mate with a 3,000 PSI SAE Code 61 motor.

This was an unfortunate mistake and one that could have been catastrophic to the system if it had been the other way around; modifying a 3,000 PSI bolt flange with a 6,000 PSI motor. An obvious system failure would have occurred, or worse a system failure that blew the assembly off causing severe damage or physical harm. This is a prime example of the importance of using only matched and properly rated components. This example illustrates the importance of properly matching flanges with each other or to

the intended component. To recommend guidelines for avoiding the mismatching of 4-bolt flanges, the Fluid Power Safety Institute (FPSI) developed the table below for common types and sizes.

Benefits of Flanges

Though there are specific applications where flanges and/or flange fittings are the only practical choice (particularly in larger, high pressure piping applications), flanges sometimes provide benefits to the piping system that traditional hydraulic fittings do not. For example, in those larger OD applications flanges are often able to be connected to pipe (tube or hose) and component ports more easily than threaded fittings or adapters. In many severe service applications on mobile construction equipment flanged connections are best for:

1.   Ease of assembly in tight spaces where wrenches might not have clearance if installing traditional fittings and they are more easily assembled with moderate torque.
   
   
2.   Hard to reach areas where flexibility is required, eliminating the need for adapters in the tube, pipe
   or hose line.
   
   
3.   Large hose, tube or pipe connections where shock, vibration, high pressure and/or pressure surges are present, which could more easily damage a traditional large hydraulic fitting.
   
   
4.   Making connections that allow for easy maintenance in rigid lines such as continuous pipes or metal tubes.
   
   
5.   Reducing the chance of components becoming loose in rigorous hydraulic applications. 

FLANGE FITTINGS & HOW THEY FIT IN

The fluid power industry is working to make a shift to using connections with an elastomeric, O-ring type seals to minimize leakage. Among other styles, these fittings include the SAE straight thread, face seal, ISO , SAE J518 (Code 61 and Code 62) flange fittings and flanges (Code 61 and Code 62), where the O-ring seal is compatible with the fluid. As covered above, when fitting tube-to-tube (or pipe or hose) a captive

flange is often used. Captive flanges simply slip over the flared tube and are connected to mating flange or other component. Captive flanges are commonly used with MJ-Flange Straight fittings (aka flange adapters), where there is smooth clearance to slide over the fitting allowing the flange head on the fitting to seat into it. Yet split flanges are used when 45° or 90° flange fittings are used (i.e. MJ- Flange 45 or 90). Split flanges come in kits (either for Code 61 or 62) which include:

• Two halves of the flange that fit around the fitting where the fitting’s flange head meets
• The accompanying O-ring seal
• Four bolts and washers to secure the flange and fitting to its intended port

Flange fitting connections are easy to assemble and provide the best option in larger diameter applications, especially when under high pressure. They provide significant advantages versus threaded fittings in these larger, more severe applications, such as:

• Easier to assemble in tight spaces
• Easy to disassemble for maintenance of reconfiguring of the system
• Large connections of over 7/8 inch up to 5 inch O.D tube or pipe – for Code 61 only
• Less torque required for tightening the four bolts versus achieving proper torque for a comparable large size fitting
• Provides up to 6,000 PSI capability through 2″ size – for Code 62 only, 5,000 PSI for Code 61
• Single point of sealing between tube, pipe, hose and/or component port connection

SAE J518 MAXIMUM WORKING PRESSURE RATINGS
FOR CODE 61 AND CODE 62 FLANGE FITTINGS

MPa (Mega Paskels) — 1 MPa = 145 PSI

Among the category of flange fittings (or flange adapters) are flanges plugs, which are used to cap off or block the flow in the pipe. Flange plugs are basically a flange without a center hole which closes the end of a pipe when bolted to a standard mating flange. Depending on the system requirements these plugs are typically gas or liquid tight. For gray water subsurface irrigation they are sometimes used to force waste through perforated holes in the pipe, driven by system pressure.

Conclusion

Though many SAE 4-bolt hydraulic flanges look quite similar to each other, SAE Code 61, SAE Code 62, and Caterpillar 4-bolt flanges exhibit small dimensional and physical differences that cannot be interchanges. It’s imperative to make sure the flanges are of the same code and the hole alignments match exactly.

Flange connections use a gasket to ensure a secure seal and are best in conditions of exceptionally high pressures in piping systems of 7/8” OD or larger. They

are used to connect pipe-to-pipe, tube- to-tube, hose-to-hose, etc. Or a single flange is used to bolt a pipe directly onto a component.

Flange fittings (aka flange adapters) are used with split and 4-bolt flanges when the mating connection is a threaded JIC 37° flare or other connection type. High quality flange fittings are made to endure extremely high working pressures and tensile strength, and are designed to perform in a variety of clearance applications. The most popular sizes of flange fittings range from 1/2” to 4”.

When fittings are involved, captive flanges are commonly used with MJ-Flange Straight fittings where there is smooth clearance to slide over the fitting allowing the flange head on the fitting to seat into the flange. Yet split flanges are used with 45° or 90° flange fittings (i.e. MJ-Flange 45 or 90).

A 4-bolt flange connection that complies with SAE J518 and ISO -1 and -2 (Code 61 and Code 62) ensures a leak-free connection and is best in larger sizes under high pressure and for assemblies in tight spaces. These 4-bolt flange port connections allow for the connection of larger sizes and attain high pressures with the capability of assembling at low torques. When compared to equivalent size threaded ports these low torque assemblies are typically the best choice in tight spaces, especially where there is limited wrench clearance.

The company is the world’s best All Flanged Tee supplier. We are your one-stop shop for all needs. Our staff are highly-specialized and will help you find the product you need.