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Flange Types: A Guide To Choosing The Right Flange

Flange originally refers to the protruding edge of the structure or mechanical parts perpendicular to the axis of the parts. People often called flange disk, according to the standard call, is “flange”, you can remove the word “disk”. Flange is to make the tube and pipe, valve accessories and other interconnected parts. Flange is divided into threaded connection (wire connection) flange and welding flange and tube flange type, is an important connection of pipeline construction.

Flange connection is the two pipes, pipe fittings or equipment, each fixed in a flange, and then between the two flanges plus flange gasket, and finally the two flanges will be tightened with bolts to make it tightly combined with a removable joint.

There are different types of flanges depending on the use, standard, material, and pressure class of the flange. This blog post will give you an idea of the common types of flanges and where to find the right one for your requirements.

Figure 1: Types of flanges

What types of flanges are there?

Flanges generally have strong sealing, tensile, bending resistance, pressure resistance, etc. Based on a variety of properties, flanges can also be divided into socket weld flanges, loose-fitting flanges, butt welding flanges, integral flanges, flat welding flanges, etc. Each flange has its own product parameters, which are shared here in detail with you.

Threaded Flanges

A threaded Flange is also known as a screwed flange, and it is having 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 not suitable for high pressure and temperature applications. Threaded Flanges are mostly used in utility services such as air and water.

  • Threaded Flange mostly used in utility services such as air and water
  • It is not suitable for high presser and temperature applications
  • It 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

Socket-Weld Flanges

Socket-Weld Flanges has 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

Slip-On Flanges

Slip-On flange has a hole with 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 available in large size also
  • 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

Lap Joint Flanges

The lap flange is having 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. 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 the carbon steel to save the cost.
  • This flange provides better joining due to butt-weld as compared to a socket and threaded type flanges
  • Not suitable for small size, Costly components, and fabrication as compared to threaded, slip-on, and socket flange.
  • 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

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 flange.

  • High skill is required for fabrication and also 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

Blind Flanges

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

Reducing Flange

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 flanges size and is considered an economical means 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.

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

5 special types of flanges

1. Weldoflange

Weldoflange is very similar to Nipoflange because it is a combination of a butt weld flange and a branch fitting connection. Weldoflange is made from a single piece of solid forged steel, rather than individual parts being welded together.

2. Nipoflange

Nipoflange is a branch pipe inclined at an angle of 90 degrees, and it is a product manufactured by combining a butt-weld flange and a forged Nipolet. While the Nipoflange is found to be a solid single piece of forged steel, it is not understood to be two different products welded together. the installation of the Nipoflange consists of welding to the Nipolet section of the equipment to run the pipe and bolting the flange section to the branch pipe flange by the pipe crew.
It is important to know that Nipoflanges are available in various types of materials such as carbon, high and low temperature carbon steel, stainless steel grades and nickel alloys. Nipoflanges are mostly manufactured in reinforced versions, which help give them extra mechanical strength compared to standard Nipoflange.

3. Elbow Flange and Latro Flange

Elboflange is known as a combination of flange and Elbolet, while Latroflange is known as a combination of flange and Latrolet. Elboflange is used to branch pipes at an angle of 45 degrees.

4. Swivel ring flange

Rotating ring flanges are used to facilitate the alignment of bolt holes between two mating flanges, which is more helpful in many situations, such as the installation of large diameter pipelines, subsea or offshore pipelines and similar environments. These types of flanges are suitable for demanding fluids in oil, gas, hydrocarbons, water, chemicals and other petrochemical and water management applications.
In the case of large diameter pipelines, the pipe is installed at one end, maintaining a standard butt weld flange, and the other end is a swivel flange. This works by simply rotating the swivel flange on the pipe so that the operator can achieve proper alignment of the bolt holes in a very easy and faster manner.
Some of the major standards for swivel ring flanges are ASME or ANSI, DIN, BS, EN, ISO, etc. One of the most popular standards for petrochemical applications is ANSI or ASMEB16.5 or ASMEB16.47. Swivel flanges are flanges that can be used in all common flange standard shapes. For example, weld neck, slip on, lap, socket weld, etc. in all material grades in a wide range of sizes from 3/8″ to 60″ and pressures from 150 to 2500. these flanges can be easily manufactured from carbon steel, alloy steel and stainless steel.

5. Expansion flange

Expansion flanges are used to increase the aperture of a pipe from any particular point to another in order to connect the pipe to any other mechanical equipment, such as pumps, compressors and valves, which are found to have different inlet sizes.
An expansion flange is usually a butt weld flange with a very large bore at the non-flanged end. It can be used to add just one or two sizes or a maximum of 4 inches to the running pipe bore. These types of flanges are preferred over a combination of butt-weld reducers and standard flanges because they are cheaper and lighter. One of the most common materials used for expansion flanges is A105 and stainless steel ASTMA182.
Expansion flanges are available in pressure ratings and sizes in accordance with ANSI or ASMEB16.5 codes, which are primarily available in convex or flat (RF or FF). Reducing flanges, also known as reducer flanges, have the exact opposite function compared to expansion flanges, which means they are used to reduce the bore diameter of the pipe. The bore diameter of a running pipe can be easily reduced, but not by more than 1 or 2 sizes. If an attempt is made to reduce beyond this, a solution based on a combination of butt-weld reducers and standard flanges should be used.

  • ① Socket weld flanges: commonly used in pipes with PN≤10.0Mpa, DN≤40;
  • ② Loose flange: loose set flange commonly known as live flange, welded ring live flange, flanged live flange and butt welding live flange. Commonly used in the medium temperature and pressure are not high and the medium is more corrosive situation. When the medium is more corrosive, the part of the flange contact medium (flange short section) for corrosion-resistant high-grade materials such as stainless steel and other materials, while the external use of low materials such as carbon steel material flange ring clamping it to achieve sealing;
  • ③ Butt welding flange: for the flange and pipe butt welding, its structure is reasonable, strength and steel degree, withstand high temperature and high pressure and repeated bending and temperature fluctuations, reliable sealing. Nominal pressure of 0.25-2.5Mpa butt weld flange with concave and convex sealing surface.
  • ④ Whole flange: often flange and equipment, pipes, valves, etc. into one, this type is commonly used in equipment and valves.
  • Flat welding steel flange: for nominal pressure of not more than 2.5Mpa carbon steel pipeline connection. Flat welding flange sealing surface can be made smooth, convex and tongue and groove type three. Smooth flat welding flange applications, more for the media conditions more moderate, such as low-pressure non-purified compressed air, low-pressure circulating water, it has the advantage of relatively cheap.

In addition, the flange installation process must be professional, usually the first joint positioning, installation of sealing ring, sealing sleeve inside with the sleeve section tapered hole. Install the ferrule, and grease the inner part of the ferrule in contact with the tapered surface of the sleeve to facilitate installation. Installation of bolts and spherical nuts, the need to grease the spherical surface and threads for installation, etc. Finally, after the completion of the installation of the two joint end face and sealing ring tendons should be in close contact without gaps.

Flange Sizing and Common Considerations

In addition to the functional design of a flange, its size is the factor most likely to influence flange selection when designing, maintaining and updating piping systems. And the interface of the flange to the pipe and the gasket used must be considered to ensure proper sizing. In addition to this, some common considerations are as follows.

  • Outside diameter: The outside diameter is the distance between the two opposite edges of the flange face.
  • Thickness: The thickness is measured from the outside of the rim.
  • Bolt circle diameter: This is the distance between the relative bolt holes measured from center to center.
  • Pipe Size: The pipe size is the corresponding size of the flange.
  • Nominal Bore Size: The nominal bore size is the dimension of the inner diameter of the flange connector.

What are the pressure classes of flanges?

Flange is a device to connect pipes or instruments, playing the role of connection and fixation. The common flange is in the form of round steel, and its shape is divided into flat plate, blind plate, high neck, flat welding, etc.. The production method is divided into forging and casting. The material is mostly carbon steel or stainless steel.
Flange is mainly classified according to its ability to withstand different temperatures and pressures. It is designated by using letters or the suffixes “#”, “lb” or “class”. These are interchangeable suffixes and also vary by region or supplier. The following common classifications are known.

  • 150#
  • 300#
  • 600#
  • 900#
  • 1500#
  • 2500#

The same pressure and temperature tolerances vary depending on the material used, flange design and flange size. However, the only constant is the pressure rating, which decreases as the temperature increases.
Since flanges are used to connect pipes or instruments, they need to have the ability to withstand pressure. Internationally, flange pressure is divided into several grades to achieve maximum pressure capacity at minimum cost. For example.

  • American system standards will flange by pounds (LB) classification: 150LB, 300LB, 400LB, 600LB, 900LB, 1500LB, 2500LB, etc.;
  • The European system uses PN to express pressure: PN6, PN10, PN16, PN25, PN40, PN63, PN100, etc;
  • Japanese system standards are expressed in K pressure: 5K, 10K, 16K, 20K, etc..

The international common pipe flange standard can be summarized as two different, and not interchangeable pipe flange system: a European pipe flange system represented by Germany; the other is the American pipe flange system represented by the United States.

What are the classification of flange standards?

At present, there are more flange standards, such as GB (national standards), JB (Ministry of Machinery standards), HG (Ministry of Chemical Industry standards), etc., and ANSI (American Standard), JIS (Japanese Standard), DIN (German Standard), etc. abroad.
However, the more commonly used standards are divided into two categories.
The DIN standard-based European system (including DIN, GB, JB, HG20592).
ANSI standard-based American system (including ANSI, GB, HG20615).
These two major categories of flanges can be distinguished by indicating the flange pressure level of the logo. (JIS standard for another class of system standards, does not belong to these two categories)

1. European flange system

European flange system: Germany DIN (including the Soviet Union)
Nominal pressure: 0.1,0.25,0.6,1.0,1.6,2.5,4.0,6.4,10.0,16.0,25.0,32.0,40.0,Mpa.
Metric diameter: 15-600mm.
Structure type of flange: flat welding plate type, flat welding ring loose-fitting type, rolled edge loose-fitting type, butt welding rolled edge loose-fitting type, butt welding type, threaded connection with neck, integral type and flange cover.
Flange sealing surfaces are: flat, concave, concave-convex, tongue-and-groove, rubber ring joint, lens and diaphragm welding surfaces.
The OCT pipe flange homologation standard issued by the Soviet Union in 1980 is similar to the German DIN standard.

2. American flange system

American flange system: the United States ANSIB16.5 “steel pipe flange and flange fittings
Nominal pressure: 150Psi (2.0Mpa), 300Psi (5.0Mpa), 400Psi (6.8Mpa), 600Psi (10.0Mpa), 900Psi (15.0Mpa), 1500Psi (25.0Mpa), 2500Psi (42.0Mpa).
Metric diameter: 6-4000mm.
Structure type of flange: strip welding, socket welding, threaded connection, loose set, butt welding and flange cover.
Flange sealing surface: concave surface, concave-convex surface, tongue-and-groove surface, metal ring connection surface.

3. JIS (Japan Standard) pipe flange

JIS pipe flange: generally used only for public works in petrochemical installations, less influential in the international arena, and no independent system has been formed in the international arena.

4. GB (national standard) system

China’s steel pipe flange national standard system GB.
1. Nominal pressure: 0.25Mpa-42.0Mpa

  • Series 1: PN1.0,PN1.6,PN2.0,PN5.0,PN10.0,PN15.0,PN25.0,PN42 (main series)
  • Series 2: PN0.25,PN0.6,PN2.5,PN4.0

Among them, PN0.25, PN0.6, PN1.0, PN1.6, PN2.5, PN4.0, a total of six grades of flange dimensions belong to the European flange system represented by the German flange, the rest of the American flange system represented by the American flange.
In GB standard, the maximum nominal pressure level belonging to the European flange system is 4Mpa, and the maximum nominal pressure level belonging to the American flange system is 42Mpa.
2. Nominal diameter: 10mm-4000mm
3. Flange sealing surface: flat, concave, concave and convex surface, tongue and groove surface, ring connection surface

5. Instrument pipe flange standard system

1. DIN standard

Commonly used pressure levels.
PN6, PN10, PN16, PN25, PN40, PN64, PN100, PN160, PN250
Flange sealing surface.
raisedfaceDIN2526C protruding face flange
DIN2512N tongue and groove face

2. ANSI standard

Common pressure class: CL150, CL300, CL600, CL900, CL1500
Flange sealing face: ANSIB16.5RFflanges protruding face flange

3. JIS standard: not commonly used

Commonly used pressure grade: 10K, 20K

What are the types of flange sealing faces?

The type of face is also a very important characteristic which has a significant impact on the final performance and service life of the flange. Therefore, some of the most important flange face types are analyzed below.

1. Flat Flange (FF)

The gasket surface of a flat flange is in the same plane as the surface of the bolt frame. Goods using flat flanges are usually goods with molds to make matching flanges or flange covers. Flat flanges should not be placed on inverted side flanges. ASME B31.1 states that when connecting a flat cast iron flange to a carbon steel flange, the raised face on the carbon steel flange must be removed and a full face gasket is required. This is to prevent the small, brittle cast iron flange from splashing into the void formed by the raised nose of the carbon steel flange.

This type of flange face is used in the manufacture of equipment and valves for all applications where cast iron is fabricated. Cast iron is more brittle and is typically used only for low temperature, low pressure applications. The flat surface allows both flanges to be in complete contact over the entire surface. The contact surface of a flat flange (FF) is the same height as the bolt threads of the flange. Full face gaskets are used between two flat flanges and are usually soft. According to ASME B31.3, flat flanges should not be mated with elevated flanges due to the potential for leakage of the resulting flange joints.

2. Raised Face Flange (RF)

The raised face flange is the most common type used in process plant applications and is easily identified. It is called convex because the face of the gasket is located above the face of the bolt ring. Each type of faceplate requires the use of several types of gaskets, including various flat ring pieces and metal composites such as spiral wound and double sheathed forms.

RF flanges are designed to concentrate further pressure on a smaller area of the gasket, thereby improving the pressure control of the joint. diameters and heights by pressure level and diameter are described in ASME B 16.5. The flange pressure level specifies the height of the face being lifted.RF flanges are intended to concentrate further pressure on smaller areas of the gasket, thereby increasing the pressure holding capacity of the joint.Diameters and heights by pressure class and diameter are described in ASME B 16.5. Pressure flange class.

3. Ring joint flange (RTJ)


When a metal-to-metal seal between mating flanges is required (which is a condition for high pressure and high temperature applications, i.e. above 700/800C°), ring joint flanges (RTJ) are used.

Ring joint flanges have circular recesses to accommodate ring joint gaskets (oval or rectangular).
When two ring joint flanges are bolted together and then tightened, the applied bolt force deforms the gasket in the flange groove, creating a very tight metal-to-metal seal. To achieve this, the material of the ring joint gasket must be softer (more ductile) than the material of the flange.
RTJ flanges can be sealed by RTJ gaskets of different types (R, RX, BX) and profiles (e.g. octagonal/elliptical for R type).

The most common RTJ gasket is the R type with octagonal cross-section, as it ensures a very strong seal (oval cross-section is the older type). However, the “flat groove” design accepts two types of RTJ gaskets with octagonal or oval cross-section.

4. Tongue and groove flange (T and G)

Two tongue and groove flanges (T & G face) fit perfectly: one flange has a raised ring, the other has a groove, they can easily fit (tongue into the groove and seal the joint).

Tongue and groove flanges are available in two sizes, large and small.

5. Male and female flanges (M and F)

Similar to tongue and groove flanges, male and female flanges (M & F face type) are matched to each other.

One flange has an area that extends beyond its surface area, the male flange, and the other flange has a matching recess machined into the facing surface, the female flange.

How are flange faces treated?

To ensure that the flange fits perfectly with the gasket and mating flange, the flange surface area needs a certain degree of roughness (RF and FF flange surface treatment only). The type of roughness of the flange face surface defines the type of “flange face finish”.
Common types are stock, concentric serrations, spiral serrations and smooth flange faces.

There are four basic surface finishes for steel flanges, but the common goal of any type of flange surface finish is to produce the required roughness on the flange surface to ensure a solid fit between the flange, gasket and mating flange to provide a quality seal.

Flange Materials

Flanges are made from the following materials.

  • Carbon steel
  • Low alloy steel
  • Stainless steel
  • Combinations of exotic materials (short rods) and other backing materials

See ASME B16. 5 and B16. 47 for a list of materials used in manufacturing.

  • ASME B16.5-NPS ½” to 24″ pipe flanges and flange fittings
  • ASME B16. 47-NPS 26″ to 60″ large diameter steel flanges

Commonly used forging material gradients 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 flange

What are flanges made of?

Flanges, gaskets, bolts and pipes are an inseparable combination in a piping system. The performance and installation of any type of product affects the sealing of the entire piping system, therefore, for a better and safer use of it, for products such as blue, it is necessary to choose them, especially flanges.
We all know that there are many types of flanges and they are classified according to their material. Generally speaking, there are two types of flanges: metal flanges and non-metal flanges, including cast iron flanges, cast steel, forged, Q235, stainless steel flanges, plastic flanges and so on. Among them, carbon steel flanges are more common, they are also the type of flange with the lowest value and maximum output; stainless steel flanges are relatively expensive and belong to the better products in flanges. So, do you know what raw materials are used to manufacture these flanges? What are the special characteristics of the raw materials chosen for flange production?
The more common material used to manufacture carbon steel flanges is Q235B, commonly known abroad as S235JR. Other materials, such as Q345, 16Mn and 20Mn are also more common, with 20Mn used in China instead of A105. among them, A105 is the more common material used in American Standard flanges and is the base material for American Standard flanges. Common materials used for carbon steel flanges in Europe include S235JR, P235GH, P245GH, P250GH, C22.8, RST37.2, etc.
The more commonly used materials for manufacturing stainless steel flanges are.

  • (1) 316 stainless steel (CF8M) can usually be used in the temperature range of -268 ° C to +649 ° C, but if it is to be used at a temperature of +425 ° C or more, the carbon content of stainless steel steel flange specifications for more than 0.04%. Therefore, flanges made of 316 stainless steel are suitable for corrosive or ultra-low temperature or high temperature non-corrosive applications.
  • (2) 316L stainless steel (CF3M) with a temperature range of up to +454°C for corrosive or non-corrosive applications.
  • (3) 304 stainless steel (CF8) has a temperature range of -268°C to +649°C. For temperatures above +425°C, the carbon content should be specified as 0.04% or more. Therefore, flanges made of 304 stainless steel are more suitable for corrosive or ultra-low or high temperatures. Corrosive applications.
  • (4) 304L stainless steel (CF3) with a temperature range up to +425°C for corrosive or non-corrosive applications.
  • (5) 347 stainless steel (CF8C) has a temperature range of -268°C to +649°C. For temperatures above +540°C, the specifications specify a carbon content of 0.04% or more, so it is mainly used for high temperature and corrosive applications.

The above is the introduction of raw materials of flanges, regardless of these flanges are too many raw materials, in fact, in the selection of raw materials of flanges, they need to be selected according to the actual use of the occasion, so as to avoid pipeline leakage.

How are flanges manufactured?

Five kinds of flange processing process steps.

1. Casting flange processing process

The selected raw materials steel into the medium frequency electric furnace melting, so that the steel temperature of 1600-1700 ℃; the metal mold preheated to 800-900 ℃ to maintain a constant temperature; start the centrifuge, the steel into the preheated metal mold; castings naturally cooled to 800-900 ℃ to maintain 1-10 minutes; cooling with water to close to room temperature, take off the mold and take out the casting.

2. Forging flange processing process

Forging process generally consists of the following processes, namely, selecting high-quality billets, heating, forming, cooling after forging.

  • 1) The flange blank is sent to the gas generator to be fired for 1.5-1.8 hours, and the temperature in the gas generator is controlled at 950-1050℃.
  • 2) When the temperature inside the gas generating furnace reaches 1050℃, drag out the flange blank and use the forging press to forge the flange blank. When the temperature of the flange blank drops below 850℃, the flange blank needs to be sent back into the gas generating furnace for firing.
  • 3) Repeat the process of 2) until all the flange blanks are forged and finished.
  • 4) Will be forged flange forging billet natural cooling to about 220 ℃, and then reheated to about 660 ℃, stop heating, so that the natural cooling to about 220 ℃, and then heated to about 660 ℃, repeated operation about 20 times.
  • 5) The flange forging billet heated repeatedly about 20 times is covered with a mixture of water and straw ash and allowed to cool naturally.
  • 6) The cooled flange forging billet for forming process to get the finished flange.

Forging process methods are free forging, die forging and tire film forging. Production, according to the size of the quality of forgings, the number of production batches to choose a different forging method.
Die forging high dimensional accuracy, small machining allowance, forging fiber tissue distribution is more reasonable, can further improve the service life of the parts.

The basic process of free forging: When free forging, the shape of the forgings is forged into the billet gradually through some basic deformation processes. The basic processes of free forging are upsetting, drawing, punching, bending and cutting, etc.

3. Die forging process

The process of die forging process: under the material, heating, pre-forging, final forging, punching even skin, cutting edge, tempering, shot blasting. Commonly used processes are upsetting, drawing length, bending, punching, forming.

4. Cutting flange processing technology

In the plate directly cut out the flange of the inner and outer diameter and thickness of the disk that leaves the processing amount, and then bolt holes and waterline processing. The flange produced in this way is called cut flange, the maximum diameter of such a flange to the width of the plate is limited.

5. Rolled flange processing technology

Cut strips with the plate and then rolled into a round process called rolling, mostly used in the production of some large flange. After the successful rolling, welding, then flattening, and then the waterline and bolt hole process.

Where to buy flanges?

Finding a trustworthy and reliable manufacturer and supplier is key to project success; turn to Yaang Flanges, we are a leading global provider of flange solutions. We bid on a wide range of products and offer technical support and customized solutions to meet your specific needs.
When you work with us, you can always work with a team of experts who are committed to providing the best products and services. YAANG manufactures and procures a wide range of flanges, including socket weld flanges, lap joint flanges, butt weld flanges, integral flanges, flat weld flanges and more.

Specifications of flanges

The specifications of flanges are composed of the following information:
Type and connection surface
A flange is specified according to whether it is, for example, “weld neck RTJ” or “socket weld RF”. ring joint face and RTJ gasket dimensions of ASME B16.5. 
Nominal Pipe Size (NPS)
This is a dimensionless designation used to define the nominal pipe size (NPS) of a connection pipe, fitting, or nozzle. Examples include NPS 4 and NPS 6. 
Flange Pressure Rating
This specifies the pressure temperature rating of the flange, which is required for all flanges. Examples include Class 150, Class 300, Class 900, and Class 1500. 
ASME B16.5 for basic flange sizes. For example, ASME B16.5, BS 1560, DIN or API 6A. 
Material specifications for flanges must be specified and are compatible with pipe material specifications. 
Pipe Schedule
This applies only to WN, composite loose and swivel ring flanges, where the flange bore must match the pipe bore, e.g. 40, 80, 120 and 160.

How to identify the flange?

Identifying the flange is one of the challenges faced by any flange buyer. The importance of these parts is often overlooked. However, their reliability is critical to the integrity of your system.
In order to find the right flange for your system, you need to identify it. This process is much more complex than using vernier calipers. In the identification process, you need to consider the following factors.

1) Identify the flange type

Finding out the type is the easiest step. You just have to look at it. The most common types of flanges are.

  • Butt weld – has a tapered hub and is mainly used in high pressure systems.
  • Slip-on – can be slipped over the pipe and welded inside and out to increase durability and avoid leaks.
  • Loose sleeve – used with the short end of a lap joint that slides over the pipe but cannot be welded and is held in place by pressure.
  • Threaded – attached to the pipe, without welding, for thick-walled pipes to form internal threads.
  • Blind – used to seal the ends of valves and pipelines, for high pressure environments.
  • Socket welding – connection to the pipe by means of a fillet weld on the outside of the flange.
  • Rotary flange – consisting of two pieces (forged welded hub and rotary forged ring).

2) Sizing
Measuring the size of a flange is not an easy task. You need to find the outer diameter, inner diameter, number of bolt holes, bolt hole diameter and bolt circle diameter.
The bolt circle diameter (B.C.) is one of the most important measurements to take when identifying a flange. This is the distance from the center of the bolt hole to the center of the other bolt hole on the other side of the flange.
3) Consider the thickness
A very important flange parameter is its thickness. It determines the amount of pressure the flange can withstand. The thicker the flange, the higher its working pressure. To measure the thickness of a flange, simply measure the outer edge of the part.
4) Read the standards
There are many standards for selecting the right flange for your needs. Depending on the application you are considering and the other components the flange will interact with, you can choose between ASME, ASTM, ANSI, API, MSS, AWWA, DIN, JIS, etc.
When selecting flanges, you may encounter ANSI (American National Standards Institute), DIN (German Standards Institute), and JIS (Japanese International Standards).
5) Handling pressure class
The pressure class of a flange determines the pressure it can withstand or work under without rupture. Each of these standards provides several pressure classes from low to high. The flange pressure class must be compatible with the pressure class of the internal working parts of the system.
6) Selecting Materials
It is important to select the material of the flange depending on the environment in which the flange will operate. Flanges may need to withstand pressure, humidity, high temperatures, corrosion, etc. They are typically made of stainless or carbon steel as well as copper-nickel.
At Epower Metals, we offer various types of flanges for many systems, including high-quality Festo swivel flanges. Our experts can help you determine the correct flange for your equipment.
Now that you’ve identified the basics of flange types, it’s time to choose the right flange for your project. Flanges come in a variety of sizes, pressure ratings, standards and materials. Be sure to choose the right flange for your project. When in doubt, always seek the help of a professional. yaang has extensive experience in the flange industry and is ready to help you with your flange needs. Visit our website today to learn more about our products and services!

Source: China Pipe Flanges Manufacturer – Yaang Pipe Industry (

(Yaang Pipe Industry is a leading manufacturer and supplier of nickel alloy and stainless steel products, including Super Duplex Stainless Steel Flanges, Stainless Steel Flanges, Stainless Steel Pipe Fittings, Stainless Steel Pipe. Yaang products are widely used in Shipbuilding, Nuclear power, Marine engineering, Petroleum, Chemical, Mining, Sewage treatment, Natural gas and Pressure vessels and other industries.)

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