Classification of flanges

What are flanges?

Flange is a kind of pipe fitting connecting pipes and valves, which is connected to the pipe end. The flange on the equipment inlet and outlet is also used for the connection between two equipment, such as reducer flange. Flange connection or flange joint refers to the detachable connection in which the flange, gasket and bolt are connected as a group of combined sealing structure. Pipeline flange refers to the flange for piping in pipeline system, and it refers to the inlet and outlet flange of equipment when used on equipment. Reducer flange is used for the connection between motor and reducer and the connection between reducer and other equipment. There are holes on the flange, and the bolts connect the two flanges tightly. The flanges are sealed with gaskets. The flange is divided into threaded flange, welded flange and ferrule flange.

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Flange connection is to fix two pipes, pipe fittings or equipment on a flange respectively, add flange gasket between the two flanges, and fasten them together with bolts to complete the connection. Some pipe fittings and equipment have their own flanges, which also belong to flange connection. Flange connection is an important connection mode in pipeline construction. Flange connection is easy to use and can bear large pressure. Flange connection is widely used in industrial pipelines. In the family, the pipe diameter is small, and it is low-pressure, so the flange connection can not be seen. If you are in a boiler room or production site, there are flanged pipes and equipment everywhere.

Classification of flanges

Classification by material: stainless steel flange, carbon steel flange, alloy steel flange, etc.
Classification by standard: national standard, European standard, American Standard, Japanese standard, Russian standard, etc.

According to the connection mode, the types of flange connection can be divided into: plate flat welding flange, flat welding flange with neck, butt welding flange with neck, socket welding flange, threaded flange, flange cover, loose flange with neck butt welding ring, loose flange with flat welding ring, ring groove surface flange and flange cover, large-diameter flat flange, large-diameter high neck flange, spectacle blind flange, loose flange with butt welding ring, etc.

Slip On Welding Plate Flange/PL

Flat welding flange is a kind of flange that inserts the pipe into the inner ring of the flange for welding,. Flat welding flange is divided into plate flat welding flange and slip on flange. Flat welding flange without neck is plate flat welding flange, that is, flat flange. Similar to the butterfly valve flange, the flange cover has the same shape as the flat flange except that there is no inner hole. Necked flanges include: necked flat welding flange, threaded flange, socket welding flange, butt welding flange, etc. generally, flat welding flange can only be connected with pipeline. If the transmission medium is class D fluid or water and steam of civil pipeline engineering, or class C fluid with low pressure, flat welding flange can be used. Its stress characteristics are between integral flange and looper flange. Due to poor rigidity, flat welding flange is not resistant to high temperature and high pressure. It is usually suitable for pipeline connection with pressure PN≤4.0Mpa.

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Plate type flat welding flange has the largest application. It is mostly used when the medium conditions are relatively mild, such as low-pressure non purified compressed air and low-pressure circulating water. Its advantages are relatively cheap, simple structure and convenient processing.
Flange standards: Ministry of chemical industry standards HG20593-1997, HG20592-2009, HGJ45-91, HG5010-58 raised face, HG5011-58 tenon, HG5012-58 concave convex, GB/T9119-2000, Ministry of machinery standard JB81-94, Ministry of electric power standard GD0506-0507, German standard DIN2573 and German standard DIN2576.

Slip On Flange/SO

The flange connection is composed of 2 flange plates, 1 gasket and several bolts and nuts. Neck flange is divided into slip on flange and welding neck flange. The flat welding flange with neck is generally used for low and medium pressure pipelines, mostly for gas valves, natural gas pipelines, etc. Compared with butt welding flange, the flat welding flange with neck can not withstand high temperature and high pressure, repeated benDINg and temperature fluctuation. Generally, the flat welding flange only needs to be welded on one side without welding the inner opening of pipeline and flange connection. The on-site installation is more convenient and popular. Compared with the plate type flat welding flange, the slip on flange is a round table (flange neck) with the inner hole slightly larger than the outer diameter of the pipe processed on the welding surface, and the pipe is inserted into the round table for welding, because a SHort neck can improve the flange stiffness and the bearing capacity. Threaded flange and socket welding flange are similar to flat welding flange with welding. Socket welding flange has high service pressure and belongs to high-pressure flange. The other side of the neck flange is the sealing surface of the flange plate, which is used for sealing with other flanges, flange covers, valves or equipment. The sealing surface of the plate type flat welding flange is full half face FF and raised face RF. The sealing surface of the neck type flat welding flange can be full plane FF, raised face RF, concave convex face FM-M and tenon groove face t-g. the two have different structures, different sealing effects and different strength. Plate type flat welding flange is used for general medium, and neck type flat welding flange is suitable for places with high flammability, explosion, corrosion and toxicity.

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Butterfly valve flange is the same as socket weld flange without neck.

Material: carbon steel, stainless steel flange
Sealing surface: FF, RF, FM-M, T-G
Flange standards: GB9116.1-2000, GB9116.2-2000, GB9116.3-2000, GB9116.4-2000, HGJ46-49-91 (46rf, 47mfm), HG20594-1997, HG20592-2009, SH3406-96, HG20616-97, ASME/ANSI B16.5.

Welding Neck Flange/WN

Butt welding flange is a kind of flange with neck, which refers to the flange SHeet with conical neck and circular pipe (straight edge section) transition and butt welded with the pipe. Neck flange is divided into slip on flange and butt welding flange. Butt welding flange connection is composed of 1 gasket, 2 butt welding flanges and several bolts and nuts. The pipe diameter and wall thickness of the butt welding flange interface end are the same as that of the pipe to be welded, and they shall be welded together with two pipes. When the thickness of the straight edge section of the neck butt welding flange exceeds the thickness of the steel pipe butted with it by more than 1mm, the straight edge section of the flange shall be thinned at the inner diameter, and the slope of the thinned section SHall be less than or equal to 1:3. The other side of the butt welding flange is the sealing surface. The sealing surface forms include: full plane FF, raised surface RF, concave convex surface FM-M, tenon groove surface T-G and ring connection surface RJ, which are used for sealing with other flanges, flange covers, valves or equipment. The nominal pressure of butt welding flange is about 1.0MPa-PN25MPa, and PN10MPa butt welding flange belongs to high-pressure flange. The butt welding flange connection is not easy to deform, the sealing effect is good, and it is widely used. It is suitable for pipelines with large fluctuations in temperature or pressure or pipelines with high temperature, high pressure and low temperature, as well as pipelines conveying expensive media, flammable and explosive media and toxic gases; The high-pressure butt welding flange with ring connection surface can be used for occasions with flammable, explosive and toxic media and high pressure. The sealing surface of the high-pressure butt welding flange is often made into concave and convex surfaces, which is suitable for pipelines with high temperature, high pressure, low temperature and large fluctuation of temperature or pressure, as well as pipelines conveying flammable, explosive media and expensive media.

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Flange standard: butt welding flange of Ministry of chemical industry: HG20595-1997, HG20592-2009,HG5014-16-58 (14rf, 15tg, 16mfm), HGJ50-53-91 (50rf, 51mfm, 53rj), machine standard butt welding flange JB82.1-JB82.4-59/94, national standard butt welding flange GB9115.1-GB9115.4-2000, Ministry of electric power standard GD0508-0509, Ministry of petrochemical industry SH3406-1996 (DN15-1500, pn2.0-42.0MPa), German standard flange DIN2627-2638 (2.5bar-400bar) American standard flange: HG20617-97, American standard butt welding flange ANSI B16.5 (1/2″~ 24″, 150Lb-2500LB), ASME B16.47 (26″~ 60″, 75LB-900LB), Japanese standard: flange: JIS B2220-2004 (DN10-600,5k-30K).
Butt welding flanges are classified according to material; Stainless steel butt welding flange, duplex steel butt welding flange, Q235 carbon steel butt welding flange, 20# carbon steel butt welding flange, 16Mn butt welding flange, alloy butt welding flange, etc
Flange specification: DN10-2000 pressure: 1.0-1.6-2.5-4.0-6.3-10.0-16.0-25.0MPa
Sealing surface form of butt welding flange: full plane FF, raised surface RF, concave convex surface FM-M, tenon groove surface T-G, ring connection surface RJ.
Butt welding flanges are classified by name: high neck butt welding flange, high pressure butt welding flange, forged butt welding flange, forged butt welding flange, large diameter butt welding flange, etc.
Scope of application: butt welding flange is widely used in metallurgy, machinery, chemical industry, petroleum, construction, engineering, shipbuilding, environmental protection, coal, machine tool, water conservancy, agricultural machinery, food, boiler pressure vessel and other industries.

Socket Welding Flange/SW

A socket is opened on the inner hole at one end of the neck of the socket welding flange, the pipe is inserted into the socket of the flange, a circle is welded on the back of the flange, and the other end is connected with other flanges with bolts. Socket welding flange, flange cover and butt welding flange belong to high-pressure flange. Socket welding flange is only applicable to pipes with nominal diameter less than 50. When using this socket weld flange, the inner diameter of the flange shall be consistent with the inner diameter of the pipe. The flange interface of the socket welded valve can also be made into a socket welded interface, and the pipe is inserted into the socket of the valve for welding. Butterfly valve flange is the same as socket weld flange without neck.

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Flange standard: GB9117.1 ~ 9117.4-2000 standard: HG20597-1997 standard: HG20592-2009
American standard flange: HG20619, ASME/ANSI B16.5, Japanese standard: JIS B2220-2004
Pressure: 1.0-1.6-2.5-4.0-6.3-10.0MPa
Sealing surface: RF, FM-M, T-G
Flange specification: DN15-50

Threaded Flange/TH

Threaded flange is a connection mode of flange. Instead of welding, the connection mode between flange and pipeline adopts threaded connection mode, that is, turn threads on the inner hole of flange, and turn corresponding threads on the pipes on the pipeline, and then connect them. The threaded flange adopts 55 ° conical internal thread RC specified in GB7306, 55 ° cylindrical internal thread RP specified in GB7306, 60 ° conical internal thread NPT (another: Pt, i.e. BSPT), specified in GB/T12716, is a 55 ° sealed conical pipe thread, belonging to Wyeth thread family. It is mostly used in Europe and Commonwealth countries, and is commonly used in water and dung gas pipe industry. The taper is 1:16. The national standard GB/T7306-2000 is called ZG in China; ZG taper pipe thread, ZG is the old code, the new code R is the taper pipe external thread, and RC taper internal thread; G is a 55 ° non threaded sealed pipe thread, belonging to the Wyeth thread family. Marked g represents cylindrical thread. The national standard can be found in GB/T7307-2001). Threaded flange is not a high-pressure flange, which is applicable to low pressure, such as engineering construction, air conditioning water system, etc., and can be used safely. Threaded flange is often referred to as a threaded product. For example, the pipe fittings on household tap water used at home are threaded. They are commonly used in engineering construction. They have the advantages of convenient on-site installation, convenient maintenance and no welding. They can be used on pipes that are not allowed to be welded, are not easy to be welded, or have poor welding performance. Threaded flange does not belong to high-pressure flange. Standard threaded flange is a flange with neck. Except that the flange is also different, other sizes of necked flat welding flange and socket welding flange are the same. One end of threaded flange is connected with pipeline thread, and the other end is connected with other flanges, flange covers, equipment, valves, etc.
The sealing surface of threaded flange is only full plane and raised surface. The threaded flange in China is only suitable for British pipe series. For the thread processing of the inner hole pipe of the threaded flange, the end of the steel pipe after tightening shall be close to but not beyond the sealing surface of the flange. When 60 degree taper pipe thread specified in GB/T12716 is adopted for threaded flange, the outer diameter of steel pipe for DN65 flange shall be 73mm; The outer diameter of steel pipe for DN125 flange shall be 141.3mm. When the 55 degree pipe thread specified in GB7306 is adopted, the outer diameter of the steel pipe for DN150 flange shall be 165.1mm.

Threaded flange is a kind of non welded flange, which processes the inner hole of flange plate into pipe thread and realizes connection with threaded pipe. Considering the structural characteristics of threaded flange, it is not suitable for flammable, explosive and hazardous occasions. The applicable pressure of threaded flange is 0.6-4.0MPa, and the diameter is DN10-DN150. Except for the inner diameter and thread size of threaded flange, other dimensions are the same as those of flat welding flange with neck.

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Flange standard: national standard GB9114-2000 aging Department: HG5008-58 chemical department: HG20598-1997, HG20592-2009
American standard flange: HG20620-1997/2009 of chemical department, American standard flange: ANSI B16.5 (1/2 ~ 24″, 150 ~ 2500lb)
German standard flange: DIN2565-2569 (DN6 ~ 150,6bar ~ 100bar), Japanese standard flange: JIS B2220-2004 (DN10-150,5k ~ 20k)
Flange specification: DN10-150
Flange material: carbon steel, stainless steel flange
Pressure: 0.6-1.0-1.6-2.5-4.0MPa
Sealing surface: FF, RF

Weld Ring Loose Flange(PJ/SE)

Loose flange, also known as looper flange, covers the flange on the pipe by flanging or steel ring. The flange can move on the pipe end. Flanging or steel ring is the sealing surface, and the function of flange is to compress them. Loose flange is divided into butt welding ring loose flange (butt welding ring + plate flat welding flange, which is equivalent to a movable butt welding flange) and flat welding ring loose flange (flat welding ring + plate flat welding flange). The flange welded by flanging is called butt welding ring loose flange PJ/SE, and the flange welded by steel ring is called flat welding ring loose flange PJ/RJ. The sealing surface of butt welding ring loose flange is raised surface RF. In general, loose flange is only connected with loose flange, not with other valve flanges.
Hg standard butt welding loose flange is also called flanging loose flange. It is often used when the medium temperature and pressure are not high and the medium is highly corrosive.

Since the medium is blocked by flanging or steel ring and the flange is not in contact with the medium, the flange can be made of low-grade materials to save materials. In addition, because the flange can rotate, it is easy to align the bolt hole. Loose flange is often used when the medium temperature and pressure are not high (not high-pressure flange) and the medium is highly corrosive. Loose flange is also suitable for places where the pipeline needs to be disassembled frequently for cleaning or inspection.

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Flange standard: JB84-1994
Standard: GB9120.1 ~ 9120.3-2000
Standard: HG20599-1997 standard: HG20592-2009 standard: HG20527-1992
American standard flange: ASME/ANSI B16.5, Japanese standard: flange: JIS B2220-2004
Sealing surface: RF
Flange specification: DN10-600

Slip On Ring Loose Flange

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Generally speaking, flat welding ring loose flange is used in one of the following three cases:

  • 1. Cost savings. When the pipe material is special and expensive, the cost of welding flanges of the same material is high.
  • 2. It is not convenient for welding or processing or requires high strength. Such as plastic pipe, FRP pipe and so on.
  • 3. Convenient for construction. For example, it is not easy to align the corresponDINg flange bolt holes during connection, or prevent the flange bolt holes from changing in the future.

Disadvantages of loose flange with flat welding ring:

  • 1. Low pressure.
  • 2. Low strength at the welding ring (especially when the thickness is less than 3mm).

Blind Flange/BL

The flange without hole in the middle of the flange cover is also called blind flange, blind flange, blind flange. The flange cover is a flange connection form of flange sheet. Generally, the thickness of the flange cover with the same pressure and size is thinner than that of the plate flat welded flange. Function 1 of flange cover: when the pipeline needs to be extended, the flange cover can be removed, and then the pipeline can be extended through flange connection. Function 2: seal the end of the pipeline to facilitate the removal of sundries in the pipeline during maintenance. The function of the flange cover is the same as that of the pipe cap and head, but the head can not be disassembled, and the flange cover is fixed with bolts, which is very convenient for disassembly. The flange cover is also a high-pressure flange. The maximum pressure of the flange cover of the Ministry of chemical industry is 25.MPa, the maximum pressure of the national standard flange cover is 42.0MPa, and the maximum pressure of the American standard flange: cover reaches 2500lb. Flange cover is the only flange without inner hole in the flange series, which is different from integral flange (valve flange), flat welding flange, butt welding flange, threaded flange, socket welding flange and butterfly valve flange. In addition, socket welding flange and butterfly valve flange are also two kinds of flanges with characteristics, both of which have two flange inner holes.

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Source: China Flange Manufacturer – Yaang Pipe Industry (www.steeljrv.com)

(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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classification of flanges - Classification of flanges
Article Name
Classification of flanges
Description
Flange is a kind of pipe fitting connecting pipes and valves, which is connected to the pipe end. According to the connection mode, the types of flange connection can be divided into:
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