Butt welding flange VS Flat welding flange

What is a butt welding flange?

A butt weld flange is a flange that has a neck and is transitioned by a round pipe and is butt welded to the pipe. butt welding flange is mainly used for the opposite welding of flange and pipe. Its structure is reasonable, its strength and rigidity are large, it can withstand high temperature and high pressure and repeated bending and temperature fluctuation. The sealing performance is reliable. The nominal pressure is 0.25~2.5MPa. The butt welding flange has a concave and convex sealing surface.

Butt welding flange production process Application range of butt welding flange
What is a flat welding flange Flat welding flange features
Flat welding flange connection application Butt welding flange VS Flat welding flange

20181212042827 51650 - Butt welding flange VS Flat welding flange

Butt weld flanges are widely used and promoted in pipe fittings and need to be used in accordance with the corresponding methods and methods.

  • Processing methods: high-precision CNC lathe turning, general lathe finishing, argon arc welding, etc.
  • Nominal pressure: sch5s, sch10s, sch20s, sch30s, sch40s, etc.
  • Manufacturing standards: national standard, American standard, Russian standard, Japanese standard, etc.
  • Connection method: flange nut, bolt connection.

Butt welding flange production process

The basic process of free forging of the butt welding flange: For free forging, the shape of the forging is gradually forged by some basic deformation process. The basic processes of free forging are upsetting, lengthening, punching, bending and cutting.

  1. Upsetting Upsetting is an operation process in which the raw material is forged in the axial direction to reduce its height and increase the cross section. This type of process is commonly used for forging gear blanks and other disc-shaped forgings. The ups and downs are divided into two types: all upsetting and partial forging.
  2. Pulling out Lengthening is a forging process that increases the length of the blank and reduces the section. It is usually used to produce shaft blanks, such as lathe spindles and connecting rods.
  3. Punching A forging process in which a punch punches a through hole or a through hole without using a punch.
  4. Bending A forging process that bends the billet into a certain angle or shape.
  5. Torting A forging process that rotates a portion of a blank relative to another portion by a certain angle.
  6. Cutting The forging process of dividing the blank or cutting the material.

The semi-finished product of the butt welding flange has a boss ring on the inner wall of the straight side of the flange body, and the upper end surface of the boss ring is flush with the upper end surface of the flange body, and the boss ring is in the butt welding flange blank Forged when forged. In the surfacing welding, the inner wall of the flange body below the boss ring is first surfacing, after the welding is completed, the boss ring is processed along the inner wall of the flange, and then the inner wall of the straight side section is welded. The addition of a boss ring at the inner wall of the straight section enhances the strength of the straight section, so that when the butt weld flange is surfacing, the deformation of the straight section is very small or substantially undeformed. After the surfacing is completed, the boss ring is processed, and the structure and size of the butt welding flange are not changed. The level of the butt welding flange of the butt welding flange and its technical requirements shall comply with the corresponding requirements of JB4726-4728.

  1. Grade I forgings are allowed for carbon steel and austenitic stainless steel forgings with a nominal pressure PN of 0.25MP-1.0MPa.
  2. Except for the following provisions, forgings with nominal pressure PN of 1.6MPa-6.3MPa shall meet the requirements of Grade II or above forgings.
  3. One of the following conditions shall meet the requirements of III and forgings:

  • (1) Forgings with flanges of nominal pressure PN≥10.0MPa;
  • (2) Forged chrome molybdenum steel with nominal pressure PN>4.0 MPa;

Ferritic steel forgings with nominal pressure PN >1.6MPa and working temperature ≤-20 degrees Celsius.

Application range of butt welding flange

The use of butt welding flange is widely used. It is the most common type of flanges. It has been well received and favored by users. So what do you need to know about the characteristics and scope of use of welded flanges? Share the butt welding here. The characteristics and application range of the flange.
Firstly, the butt welding flange is one of the stainless steel flanges, which is widely used and popularized in the machinery industry. The butt welding flange is widely used, and the scope of use is determined according to different characteristics, and is mostly used when the medium condition is moderate. Such as low pressure non-purified compressed air, low pressure circulating water, its advantage is that the price is relatively cheap. The butt welding flange is suitable for the steel pipe connection with the nominal pressure not exceeding 2.5MPa. The sealing surface of the butt welding flange can be made into three types: smooth, concave and convex and grooved. The application of smooth butt welding flange, other Two types of butt weld flanges are also common in use.
At the same time, the butt welding flange includes many types and models. The welded steel flange is used for the flange welding of the flange and the pipe. It is mainly used in the welding technology, and has good performance characteristics and performance. Its structure is reasonable, strength and rigidity. Larger, can withstand high temperature and high pressure and repeated bending and temperature fluctuations, reliable sealing, the nominal pressure of 0.25 ~ 2.5MPa butt welding flange with concave and convex sealing surface. The environment for the main application of the butt welding flange is suitable, and it needs to be determined according to the specific conditions to ensure the specific use value and performance of the butt welding flange, and to withstand high temperature and high pressure.

Butt welding flange connection and construction requirements

In plumbing, the use of flanged connections between pipes is very common. When it is more important to connect together or relatively more important and more expensive pipes, it is usually preferred to connect the welded flanges. Because the process of welding the flange itself is more complicated, and the cost price is relatively high, the performance is better than the general flange, and it is more suitable for the key parts.
There are problems in the construction method of repeated welding heads at the receiving position: one is to increase the labor intensity of workers; the other is that the repeated welding head method has high consumables, requires large equipment and has high cost. When the ball is swept by the long-distance pipeline after the pressure test, the problem of large labor intensity, high consumables, large number of large-scale equipment and high cost is adopted in the service of the repeated welding head method. Simple and quick opening flat welding flange construction method. flat welding flange is suitable for steel pipe connection with nominal pressure not exceeding 2.5MPa. The sealing surface of flat welding flange can be made into smooth, concave and convex and grooved. The application of smooth flat welding flange, other Two types of butt weld flanges are also common in use. flat welding flanges are widely used, and the scope of use is determined according to different characteristics. It is mostly used in the case of moderate media conditions, such as low pressure non-purified compressed air and low pressure circulating water. Its advantage is that the price is relatively cheap.
butt welding flange With the rapid development of long-distance pipeline construction at home and abroad, pipeline pressure testing has become an indispensable part of the pipeline. Before and after pressure testing, each pipeline must be swept through the ball, usually 4 to 5 times. . Especially after the pressure test, the water in the pipeline is difficult to clean and the number of sweeps will be more.

What is a flat welding flange?

A flat welded flange is a type of flange that is joined to a vessel or pipe by a fillet weld. It is an arbitrary type of flange. According to the degree of integrity of the connection between the flange ring and the straight section, the design is checked according to the integral or loose flange. The flange ring is available in both neck and neck. Compared with the neck-welded flange, the flat-welded flange has a simple structure and is material-saving, but the joint is not as good as the neck-welded flange. Flat welded flanges are widely used in the connection of medium and low pressure vessels and pipes.

20181212043042 34550 - Butt welding flange VS Flat welding flange

Flat welding flange features:

The flat welded flange not only saves space, reduces weight, but more importantly ensures that the joint is not leaked and has good sealing performance. The reduced size of the compact flange is due to the reduced diameter of the seal which will reduce the cross-section of the seal face. Second, the flange gasket has been replaced by a seal ring to ensure that the seal faces the sealing surface. In this way, only a small amount of pressure is required in order to press the cover tightly. As the required pressure is reduced, the size and required number of bolts can be reduced accordingly, so a new design that is small in size and light in weight (70% to 80% lighter than conventional flanges) is designed. product. Therefore, the flat welding flange type is a relatively high quality flange product, which reduces the quality and space and plays an important role in industrial use.

Sealing principle of flat welding flange:

The two sealing faces of the bolt press each other against the flange gasket and form a seal, but this also causes damage to the seal. In order to maintain the seal, it is necessary to maintain a huge bolt force, for which the bolt is made larger. Larger bolts are matched to larger nuts, which means that larger diameter bolts are needed to create the conditions for tightening the nuts. However, the larger the diameter of the bolt, the more suitable the flange becomes, the only way to increase the wall thickness of the flange. The entire device will require a great size and weight, which becomes a special problem in the offshore environment, because weight is always a major concern for people in this situation. Moreover, fundamentally, the flat weld flange is an ineffective seal that requires 50% of the bolt load to be used to squeeze the gasket, while the load used to maintain the pressure is only 50%.

Common production process for flat welding flange

  1. Round forging process of round steel pure material;
  2. Finished forging and cutting forming process;
  3. Steel plate cutting and blanking processing technology;
  4. Rough forging, expansion machine thermal expansion production process;
  5. Steel plate rolling production process, generally for large diameter flanges, such as flanges above DN600;

The above is the type of flange raw material production process, but high-precision CNC lathe turning, CNC rocker drilling, final flange forming, packaging workshop for flange printing stencil marking and packaging, the company quality inspection department to carry out inspection, The inspection report is issued and the final flange is taken out of the warehouse.
Forging of flat welded flanges can be divided into free forging, upsetting, extrusion, die forging, closed die forging, and closed upsetting. Closed die forging and closed upset forging have high material utilization due to the absence of flash. Finishing of complex forgings is possible with one or several processes. Since there is no flash, the area of force applied to the forging is reduced and the required load is also reduced. However, care should be taken not to completely limit the blank. To this end, the volume of the blank is strictly controlled, the relative position of the forging die is controlled, and the forging is measured to reduce the wear of the forging die.
According to the movement mode of the forging die, the flat welding flange can be divided into pendulum, pendulum swivel, roll forging, cross wedge rolling, boring ring and cross rolling. Swing, swivel and shackle can also be used for precision forging. In order to improve the utilization of materials, roll forging and cross rolling can be used as a front-end process for slender materials. The same rotary forging as free forging is also partially formed, which has the advantage that it can be formed in the case of a smaller forging force than the forging size. In this forging method including free forging, the material expands from the vicinity of the mold surface to the free surface during processing. Therefore, it is difficult to ensure the accuracy of the flat welding flange. Therefore, the moving direction of the forging die and the swaging process are controlled by a computer. flat welding flanges can be used to obtain products with complex shapes and high precision with low forging force.

Flat welding flange connection application

The smooth flat welding flange is the most widely used. The flat welded steel flange is suitable for the nominal pressure not exceeding 2.5MPa. The carbon steel pipe connection. The sealing surface of the flat welding flange can be made smooth. It is more suitable for medium conditions. In the case, such as low-pressure non-purified compressed air and low-pressure circulating water, the advantage is that the price is relatively cheap. The structure is reasonable, and the welded steel flange is used for the opposite welding of the flange and the pipe. The strength and rigidity are large, and the high temperature can withstand. High pressure and repeated bending and temperature fluctuations, reliable sealing. Nominal pressure is 0.25 2.5MPa. The butt welding flange adopts concave and convex sealing surface.
The flat welding flange gasket is placed between the two flange sealing surfaces. After tightening the nut, the specific pressure on the surface of the gasket reaches a certain value and then deforms, and fills the unevenness on the sealing surface, so that the joint is tight. A flanged joint is a detachable joint. There are holes in the flange, bolts can be worn to make the two flanges tightly connected, and the flanges are sealed with gaskets. According to the connected parts, it can be divided into container flange and pipe flange.
flat welding flanges are often used when the medium temperature and pressure are not high and the medium is corrosive. When the medium is corrosive. Rare integral flanges have flat and butt weld flanges. Flange fittings are flanged (flange or splicing) fittings. It can be cast, and the flat welded flange is mainly a part that connects the pipe and the pipe to each other. According to the structure type. It can also be constructed by screwing or welding. Flange joints consist of a pair of flanges, a gasket and a number of bolts and nuts.

Butt welding flange VS Flat welding flange
Distinguish the difference between flat welding flange and butt welding flange from welding method

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According to the welding methods when the flanges and the pipes are connected:

The butt weld flange is the same as the pipe to be welded at the joint end, and is welded like two pipes.
The flat welding flange is a concave table whose inner hole is slightly larger than the outer diameter of the pipe, and the pipe is welded inside.
For flat welding flange welding, only one side welding is required, and the inner joint of the welded pipe and the flange connection is not required. The welding installation of the butt welding flange requires double-sided welding of the flange. Therefore, flat welding flanges are generally used for low and medium pressure pipelines, butt weld flanges are used for medium and high pressure pipelines. Butt weld flanges are generally at least PN2.5 MPa. Butt welding is used to reduce stress concentration. The butt welding flange is mostly a neck flange and also a nipple flange. Therefore, the installation cost of the butt welding flange, labor costs and auxiliary materials costs are high, because there is more than one process.

For the butt welding flange, not all of them need to be welded inside and outside. There is no special requirement. Generally, it is only welded outside. The flat welding flange is a better welding type. Because the pipe and the flange are perpendicular to the vertical, the pipe will not oblique.

The difference in performance between butt weld flange and flat weld flange

The butt weld flange is the same as the pipe to be welded at the joint end, and is welded like the two pipes. The flat welding flange is a concave table that is slightly larger than the outer diameter of the pipe at the interface, and the pipe is welded inside. Butt welding has better welding performance and less corrosion.

  1. Stainless steel flat welding and stainless steel butt welding are the welding methods when the flange and the pipe are connected. When welding the flat welding flange, only one side welding is required, and the inner joint of the welded pipe and the flange connection is not required, and the welding flange is welded and installed. Flange double-sided welding is required. Therefore, flat welding flanges are generally used for low and medium pressure pipelines, butt weld flanges are used for medium and high pressure pipelines. Butt weld flanges are generally at least PN2.5 MPa. Butt welding is used to reduce stress concentration. The welding flange is mostly a neck flange and also a nipple flange. Therefore, the installation cost of the welding flange, labor costs and auxiliary materials costs are higher, because there is more than one process.
  2. Stainless steel butt welding flanges are not all need to be welded inside and outside, no special requirements are generally only welded outside, have not seen 1/2″ welding flange, flat welding is better welding, Because the tube and flange are perpendicular to each other, the tube will not be inclined.
  3. Stainless steel flat welding has a boss like a butt weld, a groove is formed on the boss, and then the tube is welded inside. Socket welding means that there is no boss, and a groove is directly opened on the flange body, just like a hole is opened in the blind flange, and then a groove is opened. Flat welding is better than the socket welding. Generally, I use a butt weld flange here, which can be used anywhere.
  4. Stainless steel butt welding and stainless steel flat welding flange are the two most commonly used flanges. The butt welding flange is necked, while the flat welding flange is not. If it is for safety reasons, it is best to use butt welding. If it is normal medium, the pressure is not high, and the leakage will not cause danger.
  5. Stainless steel flat welding flange: suitable for carbon steel pipe connection with nominal pressure not exceeding 2.5MPa. The sealing surface of the flat welding flange can be made into three types: smooth, concave and convex and grooved. Smooth flat welding flanges are the most widely used. Mostly used in the case of moderate media conditions, such as low pressure non-purified compressed air, low pressure circulating water, it has the advantage that the price is relatively cheap;
  6. Stainless steel butt welding flange: It is used for the butt welding of flange and pipe. Its structure is reasonable, the strength and rigidity are large, it can withstand high temperature and high pressure and repeated bending and temperature fluctuation, and the sealing is reliable. Butt welding flange with nominal pressure of 0.25~2.5MPa adopts concave and convex sealing surface.

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.)

If you want to have more information about the article or you want to share your opinion with us, contact us at sales@steeljrv.com
Please notice that you might be interested in the other technical articles we’ve published:

  • What are Lap Joint Flanges

  • When to use lap joint flange
  • How to get high quality Welding Neck Flanges

  • How to get high quality lap joint flanges

  • What are Steel Flanges

  • Lap Joint Flange VS Weld Neck Flange

References:

  • https://www.yaang.com

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