What is a pipe bend?

What is a pipe bend?

The pipe bend is a pipe fittng that is bent by a set of bending equipment, and is divided into two processes of cold rolling and hot pushing. No matter which kind of machinery and equipment and pipelines are used, most of them use bends, mainly for oil transportation, gas transmission, infusion, construction of engineering bridges, etc.

Classification of bends
1, by material:
Carbon steel: ASTM/ASME A234 WPB, WPC
Alloy: ASTM/ASME A234 WP 1-WP 12-WP 11-WP 22-WP 5-WP 91-WP911, 15Mo3 15CrMoV, 35CrMoV
Stainless steel: ASTM/ASME A403 WP 304-304L-304H-304LN-304N
ASTM/ASME A403 WP 316-316L-316H-316LN-316N-316Ti
ASTM/ASME A403 WP 321-321H ASTM/ASME A403 WP 347-347H
Low temperature steel: ASTM/ASME A402 WPL3-WPL 6
High performance steel: ASTM/ASME A860 WPHY 42-46-52-60-65-70
Cast steel, alloy steel, stainless steel, copper, aluminum alloy, plastic, argon leaching, PVC, PPR, RFPP (reinforced polypropylene).
Aluminum alloy 3003,6061, copper, copper, brass
2, divided by production methods can be divided into push, pressing, forging, casting and so on.
3. According to the manufacturing standards, it can be divided into national standard, electric standard, ship standard, chemical standard, water standard, American standard, German standard, Japanese standard and Russian standard.

4, according to its radius of curvature: can be divided into long radius bend and short radius bend. A long radius bend refers to the outer diameter of a tube whose radius of curvature is equal to 1.5 times, that is, R = 1.5D; a short radius bend refers to a radius of curvature equal to the outer diameter of the tube, that is, R = 1.0D. (D is the bend diameter and R is the radius of curvature).

pipe bending drawing - What is a pipe bend?

Bending angle (θ):15°, 30°, 45°, 60°, 90°, 135°, 180°
Straight Length (L): The length between two ends general from 300mm-1500mm
Outer diameter(D): D≤1800mm
Wall thickness(T): T≤120mm
How do you know the Bend radius(R) of pipe bend?
It is the radius of bend of the elbow with reference to a point,the point is determined by the intersection of two lines from the elbows socket end (which makes the shape of one quater of a circle). 
The bend ie; 3D bend, 4D bend, 5D bend, 6D bend, 7D bend, 8D bend, 9D bend, 10D bend, 12D bend is determined from that point of intersection as a multiple of elbows diameter.

The radius in 5D bends is five times the nominal diameter. With a 10-inch diameter pipe, the radius of the centerline of the bend would be 50 inches. Pipe bending for the specified radii is both art and science. And with today’s modern machines and advanced software, pipe bending is highly precise. With the right machine, lubrication, tooling and material, achieving the perfect bend is a sure thing.

3D Pipe bending

3d pipe bending little - What is a pipe bend?

A 3D pipe bending is a pipe bend that the bend radius is 3 times the pipe outside diameter.

5D Pipe bending

5d pipe bending - What is a pipe bend?5d bend diagram - What is a pipe bend?

A 5D pipe bending is a pipe bend that the bend radius is 5 times the pipe outside diameter.

What is 5D in bend pipe?

The RADIUS of a 5D pipe bend is actually what is 5 times the nominal diameter. So if you had a 10″ diameter pipe, the radius of the centerline of the bend would be 50 inches.

7D Pipe bending

7d pipe bending - What is a pipe bend?

A 7D pipe bending is a pipe bend that the bend radius is 7 times the pipe outside diameter.

10D Pipe Bending

A 10D pipe bending is a pipe bend that the bend radius is 10 times the pipe outside diameter.
What is the difference between a 10D bend and a 10R ell?
There is no difference. Different suppliers and contractor describe the same situation with 10R or 10D. Here is how to think about it.
A piping segment is formed or bent at a radius. The radius is measured at the centerline of the bend. The radius of the bend centerline is 10 times the nominal diameter of the piping segment being bent.
10R means the bend radii is three times the nominal pipe diameter.
10D means three times the nominal pipe diameter is the bend radii of the piping segment.
Caution doesn’t begin to convert 10R to 1.5D. Not applicable with this terminology. Standard long ells can be purchased with 10R bends, being 10 inch pipe ells have a bend radii of 30 inches.
A pipe bending machine is vital component for any pipe bending project, particularly those of a large scale. A pipe bending machine makes the job easier and is capable of completing multiple jobs in less time than when working by hand. Pipe bend, Bend pipe, Pipe bending, ANSI, ISO, JIS and DIN Standards, Measures 1/2 to 56 Inches.
The bend is used to change the direction of run of pipe. it advantage is can matach long distance transition requirements,so it is commonly that bends dimension according to customer design.

12D Pipe bending

12d pipe bending - What is a pipe bend?

A 12D pipe bending is a pipe bend that the bend radius is 12 times the pipe outside diameter.

5. According to the pressure level: there are about seventeen kinds, which are the same as the American pipe standards: Sch5s, Sch10s, Sch10, Sch20, Sch30, Sch40s, STD, Sch40, Sch60, Sch80s, XS; Sch80, SCH100, Sch120, Sch140, Sch160, XXS; the most commonly used are STD and XS.

All welded pipe fittings have bevelled end to allow for ease of welding. This bevel allows for full penetration weld in most cases. There are two types of bevels;
Plain Bevel and Compound Bevel: according to the bevel of welding pipe fittings construction.
butt weld pipe fitting plain bevel - What is a pipe bend?

Standard system
There are two main systems for the international pipe flange standard, namely the European pipe flange system represented by German DIN (including the former Soviet Union) and the American pipe flange system represented by the American ANSI pipe flange. In addition, there are Japanese JIS pipe flanges, but they are generally only used for public works in petrochemical plants, and have little impact internationally. Now introduce the national pipe flanges as follows:
1. European system pipe flange represented by Germany and the former Soviet Union
2. American system pipe flange standard, represented by ANSI B16.5 and ANSI B 16.47
3, British and French pipe flange standards, the two countries have two casing flange standards.
The internationally accepted pipe flange standard can be summarized as two different, non-interchangeable pipe flange systems: one European pipe flange system represented by Germany; the other is the American pipe flange represented by the United States. system.
IOS7005-1 is a standard promulgated by the International Organization for Standardization in 1992. This standard is actually a standard for pipe flanges that combines two series of pipe flanges from the United States and Germany.
Pipe bend production equipment
Pipe bending machines can be roughly divided into CNC pipe bending machines, hydraulic pipe bending machines and so on. The use of pipe bending machine: hydraulic pipe bending machine is mainly used for electric power construction, public railway construction, boiler laying and repairing of boilers, bridges, ships, furniture, decoration, etc. It has many functions, reasonable structure, simple operation and convenient movement. The advantages of quick installation. In addition to the function of bending the pipe, the machine can also use the oil cylinder as a hydraulic jack. Compared with the numerical control bending device, it has the characteristics of low price and convenient use, and it occupies the leading position in the domestic pipe bending machine market. CNC tube bending machine can bend the pipe in a cold state with a bending radius (single mode) or two bending radii (dual mode). It is widely used in the bending of various pipe fittings and wires in the automotive, air conditioning and other industries. . The pipe bending machine is mainly used for plastic forming of pipes.
The material of the bend is cast iron, stainless steel, alloy steel, malleable iron, carbon steel, non-ferrous metals and plastics.
The bender performs the bending of the pipe as well as the bending of the sheet. In the case of pure bending, when the tube with the outer diameter D and the wall thickness t is bent by the action of the external moment M, the outer wall of the neutral layer is subjected to the tensile stress σ1, and the wall of the tube is thin; the inner tube of the neutral layer The wall is subjected to tensile stress σ1 and the tube wall becomes thick. Moreover, the shape of the cross section changes from a circular shape to an approximately elliptical shape due to the action of the combined forces F1 and F2. When the amount of deformation is excessively large, cracks may occur in the outer tube wall, and wrinkles may occur in the inner tube wall.
The degree of deformation of the pipe depends on the relative bending radius R/D and the relative thickness t/D value, and the smaller the R/D and t/D values, the greater the degree of deformation. In order to ensure the quality of the pipe forming, the degree of deformation must be controlled within the permissible range. The bending forming limit of the pipe depends not only on the mechanical properties of the material and the bending method, but also on the use requirements of the pipe fittings. The forming limit of the pipe fittings should include the following contents:
(1) The maximum elongation deformation in the outer tensile deformation zone of the neutral layer does not exceed the plastic allowable value of the material to cause cracking;
(2) In the compression deformation zone inside the neutral layer, the thin-walled structure part subjected to tangential compressive stress does not wrinkle beyond the instability;
(3) If the pipe fitting has the requirement of ellipticity, the section of the pipe is controlled to be distorted;
(4) If the pipe has the strength requirement to withstand the internal pressure, control the forming limit of the wall thickness reduction.
The main reasons for the decline in the quality of the pipe bend and the method of attention:
1. When purely bent, the tube is thinned by the tensile stress &1 on the outer arm wall of the inner layer under the action of external force M, and the inner side is under compressive stress. The effect is thickened, and the combined forces N1 and N2 change the cross section of the tube. Based on this factor, the main cause of the deterioration of the bend quality is RX and SX. Therefore, in GBJ235-82, the RX value and the amount of external thinning under various pressure levels are clearly defined, in order to control RX. With the value of SX, thus ensuring quality.
2. As mentioned in the previous article, when the pipe is bent, the outer side of the material is pulled, and the position of the inner pressed neutral shaft is different from the pipe bending method. In the top bending type (compression bending), the neutral axis is about 1/1 from the outer wall. At 3 places, the neutral shaft is at 2/3 of the outer wall when working in a turning (back bend). Therefore, the thin-walled pipe is curved, and it is advantageous to use the spin bending method.
3, the accuracy of bending tires is also one of the factors affecting the quality of the bend. When manufacturing the bent tires, in addition to the specification and size requirements to be controlled within a certain tolerance range, the user is also required to select the corresponding bending tire according to the curved pipe diameter during use.
4. The bendability and surface corrosion of the pipe itself may also affect the quality of the pipe. During on-site construction, the operator also needs to know the material of the pipe being processed, the processing performance and the judgment of the surface corrosion.
5. R is now available. (Bending radius / tube outer diameter) relationship curve, for the user to refer to the relationship between the diameter of the pipe and the wall thickness. Reflecting the relative bending radius, the influence of the relative wall thickness on the quality of the curved pipe, according to the acceptance specification of the pipeline processing: the cold-formed steel pipeline is 4D for medium and low pressure and 5D for high pressure. Therefore, our bending tire design is R=4D (special case is different), so the tube bending machine produced by our factory mainly chooses the relative wall thickness SX, the upper part of the figure is the coreless shaft area, the middle part of the figure For the common mandrel area, the lower part of the figure is a special mandrel area. Due to the difficulty in designing and manufacturing special mandrels and the inconvenience of operation, we generally do not supply them. Special circumstances can be agreed upon separately.
6. The effect of lubrication on product quality during molding:
In the traditional production process of curved pipe, in order to obtain better surface quality of curved pipe, many methods will be adopted, including: adopting more advanced and high-grade pipe bending machine, using higher strength mold, or using lubricating products, etc. Method. With high-end pipe bending machines and high-strength molds, companies often need to invest a lot of money to complete them. Only the use of curved pipe lubrication products is relatively low-cost and fast to meet the requirements of enterprise product quality. However, in the traditional production process: oil-based bend lubrication products can meet the requirements of the company in the production of curved pipe bends, but the oil-based pipe lubrication products are not easy to clean and environmental pollution is very prominent. Therefore, enterprises must adopt more means to eliminate the impact on the quality of the final product due to the use of oil-based bend lubrication products, and put more energy and funds into it. The arrival of IRMCO bend water-based grease meets the requirements of the company for the quality of pipe bend products, and can avoid and reduce the company’s increased investment in oil-based pipe lubrication products, and fully optimize the production process.

In the application process of traditional oil-based lubrication products, the production efficiency of enterprises is greatly restricted. Because of the fluidity and extremely difficult to clean the oil-based lubricating products, it also causes pollution to the production environment and working conditions of workers. These pollutions often require a lot of money and manpower. The utility model can reduce or even avoid the above-mentioned human and material resources for cleaning up pollution, and the characteristics of no-washing and direct welding can greatly improve the production efficiency and product quality of the enterprise. The amount of IRMCO water-based bend grease can usually be reduced by 50%-80% compared to conventional lubricants, which can save the company more money.

The most commonly used process of pipe bend
Roundabout is the most commonly used method of 180 Degree Pipe Bend. According to the difference of bend equipment, it can be divided into two categories: manual rotary bend and bending machine bending. Due to the simple bending equipment, low cost of manufacture and easy adjustment and use, manual bend is not necessary, but the labor intensity and productivity are very low, which are mainly used in small batch production. The bending of the pipe fitting bend can be divided into a core bent pipe and a coreless bent pipe according to whether or not it has a mandrel.
There are many ways of pipe fitting bend. It can be divided into bending, pipe fitting bend according to the bending forming method. The mold can be divided into die bending and non die bending as the bending is used, and the core bar can be divided into core bending and non coreless bending when bending, and whether the heating can be divided into cold bending and hot bending when pipe fitting bend is bent. In recent years, new bending processes such as zero radius bending, intermediate frequency induction bending, thermal stress bending and laser forming bending have also appeared.
The mandrel type hot push pipe fitting bend is on the special push machine. Under the axial thrust, the mandrel is pushed through the horn core and the edge is heated and pushed, so that the tube billet will be expanded in the direction of circumferential and axial bending, so that the smaller diameter pipe is pushed into a larger diameter bend.

Source: China Pipe Bend Manufacturer – Yaang Pipe Industry Co., Limited (www.metallicsteel.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@metallicsteel.com

Please notice that you might be interested in the other technical articles we’ve published:






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