What are Flanges?

Flanges are used to connect valves, pipes, pumps, and other pieces of equipment to make a pipework system. Most of the time, flanges are welded or threaded, and two flanges are joined by bolting them together with gaskets to make a seal that makes the piping system easy to access. There are different kinds of these Flanges, like slip-on flanges, weld-neck flanges, blind flanges, socket-weld flanges, and so on. Below, we describe the different kinds of flanges that are used in piping systems, based on their sizes and other factors.

Types of Flanges

  • Slip On Flanges
Slip on Flange

Slip on Flange Is basically a ring that goes over the end of the pipe and has a flange face that sticks out from the end of the pipe far enough to apply a welded bead to the inner diameter. As the name suggests, these flanges fit over a pipe and are called “Slip On Flanges.” A slip-on flange is also called a SO flange. It is a kind of flange that is slightly bigger than the pipe and slides over the pipe. It has a design inside. Since the inside of the flange is a little bigger than the outside of the pipe, the top and bottom of the flange can be welded directly to equipment or pipe. It is used to put the pipe into the flange’s inner hole. Slip-on pipe flanges can be used with a raised or flat face. Slip-On Flanges are a good choice for low-pressure applications. Slip on flange is used a lot in many fluid pipelines.

  • Weld Neck Flanges

Weld Neck Flange is also called a high-hub flange or a tapered hub flange. Weld neck flange (WN flange) has a neck that can move the pipe tension, which lowers the pressure in the bottom of the flange. It can be used with high-pressure pipelines that work at high or low temperatures. Welding Neck Flanges are easy to spot because they have a long, tapered end that slowly goes through the thickness of a pipe or fitting. The long, tapered hub shields a lot and can be used in a variety of high-pressure, sub-zero, and/or high-temperature applications. A weld neck flange is a round fitting with a protruding edge that goes all the way around the circle. Up to 5,000 psi of pressure has been used successfully with Weld Neck Flange.

  • Socket Weld Flanges

Socket weld flanges only have one fillet weld on the outside, so they aren’t usually recommended for critical services. Most of the time, these are used for small-bore lines. Their static strength is the same as that of double-welded Slip On flanges, but their fatigue strength is 50 percent higher. For this type of flange, the thickness of the connecting pipe should be set to make sure the bore length is right. Before welding, there must be a space between the socket weld flange and the pipe. The goal of a Socket Weld’s bottom clearance is usually to keep the pressure at the weld root as low as possible while the weld metal hardens. The problem with the socket weld flange is that the right space has to be made. Corrosive products can get into the crack between the pipe and the flange and cause corrosion problems. This is most likely to happen in pipe systems made of stainless steel. In some processes, you can’t use this flange. Also for this flange, the pipe and fitting must always be welded together first, then the flange.

  • Blind Flanges
Blind flanges

Blind flanges are made without a bore and are used to cover the ends of pipes, valves, and pressure vessel openings. From the point of view of internal pressure and bolt loading, blind flanges are the most overstressed, especially when they are larger. Still, most of these pressures bend near the centre, and because there is no standard inner diameter, these flanges are perfect for systems with higher pressure and temperature. The purpose of these flanges is to block a section of pipe or a nozzle on a vessel that is not being used. The nozzle is often blocked off with a blind flange so that pressure checks can be done in a plant or because the user doesn’t need all of the nozzles that came with the tank.

  • Spectacle Blind Flanges

Spectacle Blinds are usually used to permanently split pipe networks or to connect to each other. A Spectacle Blind is a piece of steel that has been cut into two discs of a certain thickness.

The two discs are joined by a piece of steel that looks like the piece that goes on the nose of a pair of glasses. The name comes from the fact that the whole thing looks like a pair of glasses. One of the discs is a solid plate, and the other is a ring with the same inside diameter as a flange. Spectacle Blinds are used in places that need to be kept separate from other installations. Most of the time, the Spectacle Blind is put in the “open” position so that water can flow through the pipe. If the Spectacle Blind is turned to “close,” the pipe is blocked and no flow can happen.

  • Lap Joint Flanges
lap joint flanges

Lap joint flanges are used with stub ends when the pipe is made of an expensive material. For example, a carbon steel flange can be added to a stainless steel pipe system because the flange won’t touch the substance in the pipe. The short ends of the pipe will be butt-welded to the pipe, but the flanges will not be attached. The inside radius of these flanges has a bevelled edge so that it can clear the radius of the stub end. Lap joint flanges are almost the same as Slip On flanges, except that there is a radius where the flange face meets the bore to fit the flanged part of the Stub End. Their ability to hold pressure isn’t much better than Slip On flanges, and the assembly’s fatigue life is only a tenth of that of Weld Neck flanges. Because of this, the lap joint flange is used in low-pressure and non-critical situations.

  • Reducing Flanges

When the size of the pipe changes, reducing flanges are made to fit the new size. The flange is mostly the same size as the larger pipe size (NPT), but its bore is the same size as the smaller pipe size (NPT). Most of the time, these flanges have blind, slip-on, threaded, or welded neck flanges. They come in all pressure classes and are a great way to connect pipes that are different sizes. This kind of flange shouldn’t be used in places where a sudden change, like at a pump, would cause too much turbulence.

Made to be used in pipes with different diameters. A reduction flange is made up of a flange with a certain diameter and a separate hole with a smaller diameter. Except for the bore and hub sizes, the flange will have the same measurements as the larger pipe. Flanges of the same size that have different connecting pieces are welded, glued, or clamped together to reduce flanges.

  • Threaded Flanges

Threaded flanges look almost the same as Slip-On flanges, but the main difference is that the threaded flange has been bored out to match the inside diameter of a specific pipe. The threaded flange is a type of flange that meets ASME B1.20.1. It has taper pipe threads in its bore. It can be used in piping systems where welding the flange to the pipe is not possible, such as in highly explosive areas where welding could pose a risk. The threaded flange is attached to a pipe that has more threads than the taper pipe. Threaded flanges are usually used with galvanised and cast-iron pipes. Threaded flanges can be used in systems with very high pressure and small diameters. Their main benefit is that they can be put together without welding.

  • Square Flanges
Square flanges

Square flanges are made in accordance with JIS B2291/JIS F7806 standards. Square flanges are often used to connect pipes to each other or to other parts. Most of the time, they are used in hydraulic systems where fluids pass through lines. They are made of steel and stainless steel. A full set of square flanges includes the oring, the bolts, the female flange (where the o’ring goes), and the male flange (flat side). Part A is for the female flange. In Part B, the male flange is named. And the whole set is called AB.

Under this standard, there are three types of Square Flanges: SHAB: Used with hexagonal hex bolts, larger flange body size, SSAB is used with socket cap screws and has a smaller flange body size than SHAB. LSA is only used on the sealing side and has an L-shaped internal flow.

  • Long Neck Weld Flanges
Long weld neck flanges

Long weld neck flanges, which are often written as LWN, are used in situations with high pressure and high (or changing) temperatures, mostly in the oil and gas industry. The long neck guides the pipe into the flange and gives it strength that a standard welded neck flange cannot. This reinforcement is very important for the safety of high pressure systems in industries, businesses, and even homes. Long Weld Necks don’t have scheduled bores like many other types of flanges. Long weld neck flanges are usually made with square cuts so that they can replace the pipe instead of being welded to it.

The long weld-neck flange is usually the anchor for water mains or gas sources that are pumped into a larger network of pipes, like those in a factory or an apartment building.

  • Expander Flange

An EXPF, or expander flange, is similar to a welded neck flange, but the hub grows to a larger size (one or two sizes). It’s a good place for equipment, pumps, and vents if you don’t have much room or need to connect to a larger pipe diameter. The small size saves space compared to a reducer-welding neck flange, which can replace both the flange and the reducer. People also think that using the reducer-welding neck flange separately is more expensive than using expander flanges. Pressure ratings and dimensions meet ANSI/ASME B16.5 standards. The face of the expander flange is higher. The Expander Flange needs a single butt-weld to be installed.

  • Spade and Ring Spacer Flange
Spade and Ring Spacer Flange

Spade and Ring Spacer Flange are very similar to Spectacle Blinds, except that they are not connected. Spades and spacers are used in systems that don’t need maintenance very often or in systems with large pipes. Depending on the size of the flanges and the amount of stress, a spade can weigh hundreds of pounds. So that it doesn’t add extra weight, the flange connection isn’t used for the Spectacle Blind itself, but for 2 separate parts. A spade can be used to temporarily replace the Ring Spacer if the pipe system needs a lot of work.

  • Weldo Flange / Nipo Flange

A Nipoflange is a combination of a weldolet, a nipolet, and a Welding Neck flange. It is used in the pipe industry for 90° branch connections, just like a weldolet or a nipolet. On the side that connects to the run pipe, a weldoflange looks like a weldolet. On the other side, it looks like a flange. That means that the branch connection on the side of the run pipe is made by welding. On the run pipe side of a Nipo Flange, the branch connection is made with welding, and on the other side, it is made with a flange.

  • Orifice Flanges
Orifice Flanges

Orifice Flanges are used with orifice metres to measure how fast liquids or gasses move through a pipeline. The orifice flange is made with pairs of “Tappings” for pressure, most of which are on two sides and face each other. Orifice Flange Unions are made based on the recommendations of the American Gas Association (AGA), the American Society of Mechanical Engineers (ASME), and the International Society of Automation (ISA). Orifice Flanges come in many different styles, including the ones below: There are Raised Face weld neck orifice flanges, Raised Face slip-on orifice flanges, Ring-Type joint weld neck orifice flanges, and Corner tap orifice flanges.

  • Loose Flanges
loose flange

A loose flange is the part of a flanged coupling that is welded to the end of a pipe. The part can be made out of carbon steel or stainless steel, depending on what is needed. It is a flat steel forging with bolt holes around the edges and a hole in the middle that is the same size as the pipe that is supposed to be welded onto the loose flange. There are types of loose flanges that can be used with elbows, valves, and almost every other kind of pipeline part.

  • High Hub Blind Flanges
high hub blind flange

The High Hub Blind Flange is used to seal the pipe structures at their ends. It looks like a round plate with no hole in the middle, but it has all the right bolt holes. The high hub blind flange comes in different sizes and is made of different materials. It is used to close off the ends of pipes, valves, or nozzles. When it is closed, this flange makes it easy to get to the line. Sometimes, the high hub blind flange can be built or machined to fit the nominal size of the pipe to which the reduction is made. This could be a reduction in the number of threads or welds. Usually, high hub blind flanges come with NPT fittings that let pressure test connections be put in. High hub blind flanges are the most stressed type of flange, especially in larger sizes, because of things like internal pressure and bolt loading.

  • Screwed Flanges
screwed flanges

Screwed flanges are also called threaded flanges. They have a thread inside the flange bore that matches the male thread on the pipe. Most of the time, these flanges are used in utilities like water and air. The screwed flange is often used when the diameter is small and the pressure is high. Requirements for screwed flanges with a hub range from 1/2′′ to 24′′. Class 150 to Class 2,500, PN 2.5 to PN 250, and RF / RTJ for facing.

Screwed flanges have a bore that is threaded in the same way as the pipe’s outside thread. Pipes that have threads on the outside need flanges that can be screwed on. The good thing about these flanges is that they don’t need to be welded on.

  • Plate Flanges
Plate flanges

Plate flanges are often called “Flat flanges” because the surface of the gasket is in the same plane as the face of the bolting circle. It is also known as a flange with a flat face. Flat face flanges are often used in situations where the matching flange or flanged fitting is cast. When the counter-flanges are flat, flat face flanges are used. This condition usually happens when Cast Iron equipment, valves, and specialties are involved. ASME B31.1 says that when connecting flat face cast iron flanges to carbon steel flanges, the raised face of the carbon steel flange must be removed and a full-face gasket must be used.

Flange Facing Type & Finish:

Flange Facing Type & Finish
  • Flat Face
Flat face flanges

The Flat Face flange and the face of the bolting circular share a gasket surface in the same plane. Flat facial flanges are frequently used in applications where the matching flange or flanged fitting is cast. A flat steel flange is defined as one that is machined smooth and lacks an elevated face with ridges or a ring-shaped joint flange. The gasket has complete touch with the entire matting surface thanks to the loose flat flange.

Never attach flat face flanges with bolts to a raised face flange. According to ASME B31.1, a complete face gasket is necessary when joining flat face cast iron flanges to carbon steel flanges and the elevated face on the carbon steel flange must be removed. The term “flange face form” applies to all uses of cast iron and other brittle materials in the manufacture of machinery and valves. Only Complete Face Gaskets are to be used for “Flat Face” flanges. By doing this, the two mating flanges are made completely and equally in touch.

  • Raised Face Flanges

The most popular form of flange used in process plant applications is the Raised Face flange, which is also the most noticeable. The gasket sides are elevated above the bolting circle’s face, hence the name “uplifted face.” This style of flange mask is frequently used for all forged steel flanges, such as those on equipment and valves. The Raised face flanges allow for the use of a broad variety of gasket designs. Metallic components of the double jacketed variety as well as flat ring sheets and spiral wounds can be used in these combinations.

The Raised Face Flanges are used to improve the joint’s ability to contain pressure by applying more pressure to a smaller area of the gasket. For those flanges, the bolt holes are located in the exterior ring area. When a gasket is attached and the bolts are mounted and torqued, the “Move” adjustment between the heights of the two rings helps more force be applied to the gasket area, creating a stronger seal. The flange face is either 1/16′′ or 1/4′′ elevated, depending on the pressure class; ANSI 300 and lower have a 1/16′′ face raised, while ANSI 400 and higher have a 1/4′′ face raised.

  • Ring joint flanges (RTJ)
Ring joint flanges (RTJ)

Steel ring gaskets are cut into the sides of ring joint flanges (RTJ) by the grooves on their surfaces. The gasket between the flanges is closed (or coined) when bent bolts press into the slots, and the flanges make close contact with each other inside the grooves, bonding the metals together. In systems over 427 °C with high pressure and severe temperature, Ring Style Joint flanges are typically used. There could be a raised face on an RTJ flange with a ring groove machined into it. No part of the sealing mechanism is acted upon by the elevated face. In the case of RTJ flanges with ring gasket seals, the elevated faces of the connected and tightened flanges may come into contact.

The ring connection gasket material must be more ductile (less strong) than the flange material for this to happen. Beyond the tension of the screw, the stretched gasket will not be able to endure additional loads, and motion and vibration won’t be able to further weaken it and lower the connection voltage. The most popular RTJ gasket is of the R variety, which features an octagonal section, as it ensures an incredibly strong seal. However, a “simple groove” style acknowledges that the RTJ gaskets both have an octagonal or oval section

  • Groove & Tongue Flanges
Groove & Tongue Flanges

The tongue and groove flanges must fit the openings of the tongue and groove. A raised ring (called a tongue) is machined onto the face of a flange on one side, and a matching depression (called a groove) is machined into the nose of the mating flange. Tongue-and-groove facings come in both big and small sizes and are standardised. In contrast to male and female, these retain the gasket on its inner and outer diameters because the tongue-and-groove interior diameters do not extend into the base of the flange. These are frequently found on pump covers and valve bonnets.

The fact that tongue-and-groove joints are self-aligned and act as an elastic cushion is another advantage. The scarf joint eliminates the need for a labor-intensive machining procedure while holding the loading point in line with the joint. Bolting is not permitted on some flange faces, including the RTJ, T and G, and F and M. This is due to the fact that the touch surfaces do not overlap and there isn’t a gasket that has a different variety on each hand. In low pressure, non-critical uses, Groove & Tongue flanges are used to connect other Groove & Tongue components.

  • Male & Female Flanges
Male & Female Flanges

Flanges that want to suit one another are known as male and female flanges. These variants have one flange face that extends beyond the typical flange face in one area. It’s called The Man lip. An identical depression will be machined into the nose of the other flange, which could be the mating flange. The “Woman flange” refers to this connecting flange.

Additionally, the flanges need to line up with this shape. There is a region on each facial flange that extends past the flange’s usual face (Male). The face of the other flange, or mating flange, has a similar depression (Female) machined into it.

The male faces are supposed to be 1/4-inch broad and flat on each end, while the female faces are supposed to be 3/16-inch long. The exterior diameter of the feminine visage finds and holds the gauze. In reality, there are two types: Wide M&F Flanges and Middle M&F Flanges.

Male and female flanges have enhanced sealing capabilities, more precise placement and compression of the sealing material, use of other, more effective sealing material, and advanced sealing material (O-rings).

Different Types of International Standards for flanges:
  • ASME B16.5 Flanges
ASME B16.5 Flanges

The pressure classes 150 to 2500 of the ASME B16.5 specification apply to flanged fittings and NPS 1/2 through NPS 24 Metric/Inch steel pipe flanges. This covers pressure-temperature ranges, elements, lengths, tolerances, naming, measuring, and approaches to marking openings for pipe flanges and flanged fittings. Weld neck and blind flanges are two very important flanges that are frequently used for piping systems. The terms “B16.5” or “B16.5,” which refer to the same standard, are interchangeable. However, the normal ASME B16 5 (ANSI B16 5) only contains dimensions up to 24 inches.

ASME B16.5 is the latest and accurate standard. ANSI B16.5 is extensively used by manufacturers, suppliers, engineers, and architects in the lingo industry. ANSI B16.5 standards are not strictly real, but they were used as a different way of saying ASME B16.5.

  • ANSI B16.47 Flanges
ANSI B16.47 Flanges

The ANSI B16.47 (Large Diameter Steel Flanges) specification covers steel pipe flanges with a diameter range of NPS 26 to NPS 60. Even so, the standard ANSI B16.47 is further divided into Weld Neck flange, Blind Flange, ANSI B16.47 Series A, and ANSI B16.47 B flange. Previously known as the Series B flange, the API 605 flange. The terms B16.47, B16.47, and ANSI B16.47 are equivalent and follow the same specification.

The most recent edition offers scores in units and metric and inch measurements. API 605 and MSSSP-44: Steel Piping Flanges Carbon steel flanges with a wide diameter are installed on the ANSI B16.47. In accordance with this specification, the API 605 flanges are referred to as ANSI B16.47 Series B flanges while the MSS SP-44 flanges are known as ANSI B16.47 Series A flanges. The ANSI B16.47 standard specifies the criteria for pipe flanges in sizes NPS 26 to NPS 60 as well as classification grades 75, 150, 300, 400, 600, and 900 for bigger sizes in terms of pressure temperature, parts, dimensions, tolerances, marking, and examination.

  • BS 10 Flanges
BS 10 Flanges

The specification for cylinders, tubes, fittings, flanges and bolting design is British Standard 10 from 1962. Boss, simple, integrally cast or etched, and neck welding style flanges are among the BS 10 flange sizes available in mm, according to the BS 10 Tables. Although outdated, the BS 10 flange chart for light-duty spans, inexpensive stainless steel flanges is still in use. This is in contrast to the BS 10 table of pipe flanges. Heavy metals and alloys, such as stainless steel, carbon steel, and alloys made of elements like nickel, copper, and others, may be used to create these BS 10 type flanges.

One of the most affordable options is to use BS 10 flanges, which are known for both their dependability and excellent performance. Both under high pressure and high temperature conditions, the BS 10 neck flanges perform well. Depending on how the component will be used, the BS 10 table d flanges may also be made of grades of stainless steel like duplex and Super duplex.

  • DIN Flanges
DIN Flange

German national standardization group Deutsches Institut für Normung (DIN), an official ISO affiliate body, is part of the German Institution for Standardization. The division flanges are known as DIN Flanges, according to a German Registered Organization with headquarters in Berlin. There are currently about 30.000 DIN standards, which encompass almost all technological fields. The majority of European nations specify DIN flanges.

Metric dimensions (mm and bar) are used by DIN standard flanges to determine the sizes and pressures of the valve and flange. Even if the flanges are manufactured in the United States, European companies usually use the DIN standards. Over 30,000 DIN standards for flanges offer thorough covering for a variety of flange products and technologies. DIN flanges have a broad application. Flanges that meet the DIN specification have DIN Numbers beginning at 15, 20, 25, 32, 40, 50, 65, 80, and so on up to 200.

  • EN 1092-1 Flanges
EN 1092-1 Flanges

The British Standard of Specification has an extension known as EN 1092-1. This replaces the defunct BS EN 1092-1. in BS EN 1092-1. A European metric variety of circular flanges with 2, 5, and 100 PN designations and DN sizes ranging from 10 to 4000. This EU standard specifies the dimensions and PN codes for circular steel flanges with nominal sizes ranging from DN 10 to DN 4000.

A flange’s forms, facings, lengths, tolerances, threading, fastener sizes, surface texture, labelling, materials, pressure/temperature levels, and weights are all specified in the specification. The following range of materials and sizes are available for the crude, coal, petrochemical, and related sectors using EN 1092-1 Form 01 pn10 Flange: The following carbon steel materials are used to make EN 1092-1 flanges: A105, SS400, SF440, RST37.2, S235JRG2, P250GH, C22.8. Additionally, these are made from stainless steel grades F304, F304L, F316, F316L, 316Ti, and so forth.

  • BS 4504 Flanges
BS 4504 Flanges

BS 4504 Circular flanges between PN 2.5 and PN 40 for cylinders, valves, and fittings are included in the British metric system for flanges, along with flanges with DN measurements. It was formerly designated as BS 4504: 1969. These flanges are perfect for use in demanding situations, particularly in low-pressure oil industry applications. A European metric standard for circular flanges includes 2, 5, and 100 PN names and DN sizes ranging from 10 to 4000.

The ANSI B16.5, B16.47, and B16.36 flange specifications are all included in the BS 4504 Flanges. Additionally, they include DIN codes like DIN2527, DIN2566, DIN2573, DIN2576, DIN2641, and DIN2642. These BS 4504 flanges are used in a variety of sectors, including the chemical, fertilizer, heat exchanger, instrumentation, and nuclear thermal businesses.

  • JIS Standard Flanges
JIS Standard Flanges

Japanese company operations must adhere to Japanese Industrial Standards, or JIS. This was arranged by the Japanese Industrial Stands Group (JISC). The Japan Standards Association (JSA), which was formerly a division of METI, is now a separate charity. This is built with a variety of programmes for both Japanese and global standards. According to the different sizes they can be produced in, the JIS Standard Flanges are grouped under the JIS-B section.

These JIS (Japanese Industrial Standard) flange varieties are divided into JIS5k, JIS10K, JIS15K, and JIS20K categories. By changing the K to one of the previously stated categories, such as 5K, 10K, 15K, or 20K, the JIS B2200 K Flanges are defined. The categories or kinds of flanges affect each flange’s dimensions.

Materials used to Manufacture Flanges:

These steel flanges are made of a variety of materials, including carbon steel, low alloy steel, stainless steel, duplex steel, super duplex steel, monel, inconel, hastelloy, nickel, and a combination of exotic materials (Stub) and other supporting materials.

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