Elbows are a special part that allows you to perform a smooth turn of the pipeline. They are used when it is necessary to change the direction of the structure. It is a piece of pipe with a bend at the desired angle. Mounted by butt welding. Elbows are produced on special pipe bending machines in full compliance with GOST. They are used in almost all industries. Most often used in the installation of boiler, oil, gas and plumbing systems.

Varieties

Branches are classified depending on the material from which they are made, diameters, bending angle. Each product has its own brand. Details are produced according to various points of GOST. You can find out all the information about the product by its labeling.

Steel bends for pipes are made of various types of steel: stainless steel, carbon, alloy. The type of steel used depends on the industry in which the part will be used, the environmental conditions, and the specifics of the work. Steel products are usually required for pipes with nominal bores up to 50 mm. Steel fittings are classified according to the method of production: seamless and welded. Seamless products are distinguished by higher consumer qualities. There is also a classification according to manufacturing technology: cold-formed, stamped and much more. The choice of a particular product is determined depending on the working conditions. For example, sectional products are used for the installation of large diameter pipes.

Steel bends have a wide range of applications. They can be used in both domestic and industrial applications. In the event that the products are used in industrial conditions, their operating temperature ranges from - 70 to + 450 degrees. Also, the parts must not come into contact with aggressive substances. The working pressure of the product is 16 MPa, the standard diameter is 32-426. Steel fittings are often used in energy and industrial applications.

It is also worth noting the bends for HDPE pipes. Their main advantages:

• Corrosion resistance;
• Resistance to aggressive environments;
• Flexibility;
• Strength;
• Guarantee of stable pressure in the system during its operation;
• Light weight.

Products made of HDPE, due to their lightness, can reduce transportation costs. In addition, the details allow you to save on installation. When installing elements from HDPE, special construction and welding equipment is not required.

PVC pipes are also popular. Consider their main advantages:

• Ease;
• Long service life (up to 50 years;
• Easy to install;
• Democratic price.

In addition, PVC products are resistant to ultraviolet radiation, moisture, aggressive substances, temperature changes, and corrosion. During their operation, you can be sure that there is no overgrowing of sections. PVC fittings are easy to install. No special equipment is required for their installation. Details are connected according to the principle of the designer. A person who does not know the appropriate experience and knowledge will be able to cope with the installation.

Branches for pipes are subdivided into bent and welded. Sector welded parts are made from a wide variety of steel types (carbon, heat-resistant, low-alloy and much more). Designed for systems of food, chemical, energy value and many other systems. Segment grades are made by welding wedge-shaped rings. Are applied to transportation of gas and water under small pressure. They are usually used when it is required to fasten large diameter pipes together. You can see how these or those pipe bends look in the photo.

Diameters and dimensions

Standard bend angles:

• 15 degrees;
• 30 degrees;
• 90 degrees;
• 180 degrees and others.

The choice of product depends on the size of the pipe. The diameter of the bends themselves ranges from 426 to 2,000 mm. If necessary, you can order a design with a non-standard deflection angle or diameter. Standard parts are produced according to GOST:

• GOST 17375-2001. Regulates the production of products with a nominal bore of 1.5, bends at 45, 60, 90 and 180 degrees. The standards apply to seamless weld fittings made of various types of steel. The diameter can be from 32 to 320 mm, wall dimensions - 2-32 mm;
• GOST 30753-2001. Regulates the production of seamless welded products. It refers to steel structures. The bend can be 90, 60, 35, 180 degrees, diameter - 57-820 mm. The dimensions of the wall of products vary from 4 to 36 mm;
• GOST 17380-2001. Regulates the production of seamless welded steel parts. You can use such products at temperatures from -70 to +450 degrees;

• GOST 22793-83. Regulates the production of bent products.

You can supplement the theoretical information about pipe bends with the help of a photo. The choice of product depends on the characteristics of the pipeline and operating conditions.

Pipelines are used to transport various working media. Pipelines are necessary to supply heat and water to homes, as well as to enterprises in various sectors of the economy. An important element of the pipeline are steel bends that allow you to change the direction of movement of the working medium.

Types of steel bends

A steel bend is a piece of pipe bent at the required angle. Steel bends are divided into types depending on the material, diameter, bending angle, as well as the production method.

Steel of various types can serve as a material for bends:

• carbonaceous;
• stainless (alloyed);

According to the method of manufacture, the bends are divided into the following types:

• steeply curved seamless;
• stamp-welded;
• welded sector;
• bent.

Bent bends are cold-bent and hot-bent.

Steel bends for pipes

Branch material

For the correct choice of the material from which the branch will be made, it is necessary to take into account the conditions of its operation, the necessary reliability of this element, as well as the aggressiveness of the working environment in which it operates.

For example, in general-purpose pipelines, bends made of carbon steel are used.

In the presence of an aggressive environment that can cause corrosion of the material, alloyed and stainless steels are used. Elbows made of such steels are used in pipelines for the oil and gas, chemical, food or pharmaceutical industries.

For example, 12X18H10T stainless steel bends can be used in pipelines transporting steam, hot water, alkaline, acidic and other working media prone to metal corrosion. Elbows made of 3XFA alloy steel can operate at ambient temperatures from -60 ºС to + 40 ºС, working medium temperature up to +40 ºС and pressure up to 7.4 MPa. Such bends have increased resistance to corrosion in the cold and are used in oil and gas systems in the conditions of the North.

According to SmartInox specialists, in order to correctly select the material from which the branch will be made, it is necessary to take into account the conditions of its operation, the necessary reliability of this element, as well as the aggressiveness of the working environment in which it operates.

Design features

Angled Elbows

The main characteristics of curved bends are given in GOST 17235-2001, GOST 17235-83 and other documents, including various departmental specifications.

Steeply curved seamless elbows are made by pulling a piece of pipe through a special mold. This method allows you to get a high quality output. Elbows of this type are produced both from carbon steel (type steel 20) and stainless steel (type 10X18H10T). In this case, the bends can have a bending radius from one Du to one and a half Du (Du is the nominal diameter of the pipe), with angles of 30º, 45º, 60º and 90º. The diameter of such a branch can be from 18 to 426 mm and it must withstand pressure up to 16 MPa.

Twisted Elbows

Stamp-welded bends

Stamp-welded bends are made from stamped steel sheets by welding. This method allows you to create a branch with a thick wall and a diameter of up to 1420 mm. These bends are used in the main pipelines of the oil and gas industry. The material for such taps is structural, stainless or alloy steel. In this case, the regulatory document is departmental specifications (for example, TU 102-988-95).

Stamp-welded bends

Sectional bends

Welded sectional bends consist of individual sectors of pipes that are welded together. This design is cheaper, but it is less reliable. Typically, bends of this type are used in pipelines operating at low (up to 2.5 MPa) pressure and temperature not higher than +425 degrees. The permissible diameter ranges from 108 to 1620 mm. Branches of this type are made of carbon or low alloy steel and are used in thermal power plants.

Sectional bends

Bent bends

Bent bends are usually used when it is not possible to use sharp bends. The difference between the former and the latter is that the latter have a much larger bending radius and a straight section. Bent bends can have a bending radius from 2 to 20 Du, and a bending angle of 2º - 90º. Such bends are made in accordance with GOST 24950-81 and TU and can be used in pipelines with pressure up to 100 MPa and temperatures from -50 to +510 ºС.

Bent bends can be cold or hot bent on special pipe bending machines. The presence of a straight section in such bends increases their weight, which is a disadvantage.

Bent bends

Branch welding

Welding bends with pipes is a rather responsible operation. It must be carried out by highly qualified welders.

In this case, various types of welding can be used - gas welding, manual arc welding (RDS), automatic submerged arc welding, in shielding gases, and the like.

When welding pipes and bends, a number of requirements must be met, which are set out in the relevant instructions, for example, VSN-006-89.

Before welding, it is necessary to check the welded surfaces of the branch and pipe. All detected external and internal defects must be eliminated.

It is necessary to control the displacement of the inner edges. For example, when connecting elements with equal diameters, such an offset should not be more than 2 mm.

Centering of welded products is carried out using centralizers or rotators.

With RDS, welding of the first root weld is carried out with direct current. In this case, in the event of a break in welding, it is necessary to maintain the preheating temperature in this place.

After welding and grinding of the root weld, a second pass is made, which must be carried out along the hot root weld. The time between these two processes should not exceed 5 minutes.

Next, filling joints and a facing joint are performed. In this case, it is necessary to ensure the temperature of the seam is not lower than +5 ºС. The facing seam should overlap the main layer of the pipe by 2.5-5 mm and have a height of 1-3 mm more than the level of the pipe wall or bend.

For welding bends in production conditions, various devices and entire complexes are used.

The most common are pipe rotators. The principle of operation of such a rotator is that the elements of the pipeline are clamped in special clamps and rotate around its axis. This facilitates and improves the quality of manual welding or automatic welding.

A feature of welding a pipe with a branch is that the system must work taking into account the uneven distribution of masses. To solve this problem, the rotator uses servo drives and special supporting racks with rollers.

The advantages of using such a rotator are as follows:

• work with pipes of large diameters;
• thanks to an autonomous drive, the ability to change the speed of rotation of the pipe;
• precise centering of the parts to be welded. In this case, the clamping rollers themselves act as a centralizer;
• the ability to work with both straight pipes and complex pipe parts (bends, tees, flanges).

Welding of steel bends

Pipe rotator

On sale there are a large number of models of pipe rotators made in China, Germany, Russia.

For example, the middle pipe rotator from the U500 series (Germany) is designed to rotate welded pipe parts by 360º. It also allows the workpiece to be tilted, which is useful when welding complex parts such as bends.

This unit has the following features:

• adjustable workpiece rotation speed - 0-130 cm / min;
• diameter of clamped pipes - 20-400 mm;
• tilt moment - up to 7500 kg-cm;
• vertical load capacity - up to 500 kg;
• torque of rollers -2000 kg-cm;
• power consumption from the network - 750 VA.

The U500 pipe rotator can be equipped with a semi-automatic welding control unit. In this case, the burner is mounted on a support that allows you to move the burner to the desired location.

Thanks to the control unit, the operation of the rotator and the welding unit is synchronized:

• arc ignition;
• workpiece rotation;
• seam overlap.

Pipe rotator

1. To change the direction of transportation of the working medium in the pipeline, steel bends are used.
2. Depending on the operating conditions and technical requirements of the pipeline, bends of various designs made of different steel grades can be used in it.
3. Welding of bends with pipes under production conditions is carried out using pipe rotators from different manufacturers.

Steel bends- these are the connecting parts of the pipeline system, allowing you to smoothly change the direction of the pipeline.

When laying a pipeline, it becomes necessary to go around obstacles, structures, or simply change the direction of the pipeline. In this case, steel bends are used. 90 degree elbows are the most common, but 30, 45, 60 and 180 degree steel elbows are also used. Branches connect pipes of the same diameter.

According to the method of manufacture, the branches are divided into:

Flanged bends are also quite common in the construction of pipeline structures. The flange outlet has become widespread due to lower labor costs during the installation of structures. The presence of a flange welded to the bend at the factory increases the speed of pipeline assembly, since the bend is bolted to the pipe (no need for welding) and does not require qualified personnel. Another important plus is the ease of dismantling during repair work. You can find out the prices for flange outlets by contacting our managers, since this item is custom-made, the price will depend on the volume.

Application:

The importance of bends in the installation of pipeline structures cannot be underestimated. Steel bends allow you to go around obstacles during the construction of the pipeline.

Steeply curved bends are the most versatile, as a rule, they are used in main and industrial networks, the oil and gas industry, in the construction of housing and communal services, under conditions of permissible pressure up to 160 atm. and temperature range from minus 70 to plus 450 °C.

Bent bends benefit in cases where it is not possible to use steeply curved products, in cases where a larger bending radius is needed. Bent bends are applicable in almost any kind of pipeline structures.

Sector welded bends are most often used in the construction of pipeline structures for heating networks and thermal power plants, where products of large diameters are needed. The scope of operation of welded bends includes the transportation of non-aggressive oil products, steam and hot water.

In conditions of high humidity, stainless steel bends are used. Stainless products are widely used in extreme conditions, with sudden temperature changes, when transporting a working medium of various aggressiveness (oil industry, technological pipeline networks).

For the smooth functioning of residential buildings, industrial facilities, social facilities, it is necessary to establish a correct, functional and reliable system for providing buildings with water, gas, and heat energy.

In industrial facilities, it is required to provide the possibility of supplying various process gases, steam, fuels that will be used in the production cycle of the enterprise.

And pipelines carry such an important function. They consist of pipes of various diameters, as well as various components and parts that are designed to help create a complete system. Such nodes are called pipe fittings. It includes: bends, flanges, plugs, adapters and tees.

Pipe bends are a part that is designed to smoothly change the direction of the pipeline to the desired angle. In other words, it is a small piece of pipe, curved at the required angle. Its manufacturing technology is diverse, because it comes in several types.

Bent models are made on pipe bending machines. Their production is very cheap. Their disadvantages include the fact that they have a large bending radius, therefore, during the production process, microcracks can form and the profile can be deformed.

As a rule, they are made for pipelines with a nominal diameter not exceeding 50 mm. The marking is applied in accordance with the nominal bore diameter. Recently, they have been significantly squeezed out of the market by forged parts.

The figure shows a curved pipe steel bend

The technical characteristics of such pipes are presented in the table:

These bent elements are often equipped with threads for easier and faster installation. For example, it is very convenient to use a gas pipe outlet with a threaded thread.

Forged models are the most common variety. Their manufacture occurs in various ways, but a prerequisite is the heating of the workpiece. Marking is applied in accordance with the outer diameter of the pipe.

All products that are used in industry for laying main pipelines have a special marking, which additionally indicates their resource, in accordance with the operating conditions. At present, when induction plants for the manufacture of pipes with a diameter of 15 to 1400 mm have appeared, this technology is gaining more and more popularity.

Segment (sector welded, welded) models are pipe bends made by welding wedge-shaped rings. They are quite cheap to manufacture. They are used in systems where it is necessary to connect large-diameter pipes for the removal of gases and water under low pressure.

Sector welded (welded) parts are made of low-alloy, high-alloy, carbon, corrosion-resistant, heat-resistant and heat-resistant steel. They are intended for use in the food, energy, petrochemical, pharmaceutical, pulp and paper, metallurgical, chemical industries. Cold water, oils, hot water, fats, aggressive and non-aggressive mixtures are the normal working environment for systems with such steel elements.

The most commonly used steel grades are: st20, st09G2S, 3PS/SP5, st12X18N10T. Elbows are manufactured from 426 mm to 2000 mm in diameter. Bending angles can be 180, 90, 60, 45, 30, 15 degrees. Under the order, models are made with any angle of rotation according to individually developed drawings of the customer. Typical ones are regulated by the following GOSTs.

• GOST 17375-2001 - Symbols, dimensions and design of bends for pipelines correspond to the 3D type, have a nominal bore R = 1.5DN and a turn of 45, 60 90 and 180 degrees. These are seamless, steeply curved welded parts. They are made from low alloy steel or carbon steel. Used in the manufacture of stamping or stretching methods on a horn-shaped rod. Products of I execution are made with an angle of 180, 90 and 45 degrees. Their diameter can vary between 21.3-1016 mm. The material for the pipe from which they are made has a thickness of 2-12.5 mm. Products of II execution are made with an angle of 180, 90, 60 and 45 degrees. The diameter varies between 32-320 mm with a wall thickness of 2 to 32 mm.
• GOST 30753-2001 - Welded seamless elements made of carbon and low alloy steel. Type 2D. They are made in the same way as in the GOST described above. Products of I execution are made with a bend of 180 and 90 degrees. Its diameter is in the range of 60.3-610 mm, the wall thickness is 4-12.5 mm. Products of II execution are produced with a bend of 180, 90, 60 and 45 degrees. Diameter from 57 to 820 mm, wall thickness from 4 to 36 mm;

Manufacturing standards are OST 34 10.752-97, OST 36-21-77.

Forged stamp-welded parts (OKSH) are used for main pipelines, which are required to work under high pressure. In their manufacture, the technology of stamping two halves (along the direction of the pipe) is used, then the halves are connected by welding.

This technology allows you to get a ready-made branch for water and gas pipes with a large wall thickness and large diameter. The quality control of the finished product is carried out over the entire surface in order to exclude the presence of cracks absolutely.

Pipeline elements (pipes, bends, tees, transitions) are manufactured strictly according to industry standards, current GOSTs and TUs. In addition, they undergo a thorough quality check: chemical analysis, express analysis of the chemical composition, metallography, analysis of mechanical properties, magnetic particle flaw detection, sound flaw detection, hydraulic testing.

In domestic pipelines, so-called plastic pipes (polypropylene) are currently successfully used. The diameter of those used to supply water in a residential apartment is not subject to strict standards. The only thing to consider is the size of the water and sewer pipes that enter the apartment from the outside. Most often, products with a diameter of 20-25 mm are used for risers. Their installation is quite simple and does not require special skills or equipment.

The advantages over metal pipes are obvious. The most important and first advantage is their service life. It can be over 50 years old. In addition, they have a fairly aesthetic appearance and do not require painting, because they are not afraid of corrosion. Such pipes have good thermal insulation properties, are resistant to high temperatures (water temperature can reach 95 degrees Celsius) and water hammer.

Elbows for polyethylene pipes withstand a nominal pressure of 6.3-10 atm (Kgf cm).

The drawing shows an image of the outlet. The main dimensions of typical pipes for water drainage and their connections are presented in the table:

Pipes for the removal of gases (flue) are intended for use in industrial and heating installations that operate on both liquid and solid fuels. They are designed for use in 1-3 wind regions with air temperature from -40 to +40 ºС and seismic activity up to 6 points. The choice of material for them depends on the composition of the exhaust gases.

Chimneys are of two types: with an underground junction of gas ducts and above ground. They consist of trunks and stretch marks. Staples are installed on the trunks for servicing the guys themselves and light protection lights. Stretch marks are arranged in several tiers, depending on the height of the pipe.

A pipe for removing exhaust gases from a car (exhaust) is used to remove fuel processing products outside the car body. The main such products are: hydrocarbons and nitrogen oxides, carbon monoxide (CO, CH, NOx). Due to damage to the exhaust gas system, almost the entire periodic table can get into the atmosphere. In addition to damage to the main pipe, there may be a loss of tightness of the joints, damage to the gaskets. The path of exhaust gases in the vehicle exhaust system is shown in the diagram.

According to the material from which the car muffler is made, they are divided into four types.

1. aluminized,
2. aluminum-zinc,
3. stainless,
4. made from black steel.

Each muffler has a number of both advantages and disadvantages. The most popular aluminized mufflers. They are the most practical. Silencer models made of this material are installed on almost all foreign cars.

The service life of such a muffler is 3-6, and the price is slightly higher than for similar models made from other materials.

Types of steel bends

• Tightly curved seamless are made of carbon and low-alloy steel with bending angles of 45, 60, 90 and 180° from pipes by stamping or drawing along a horn-shaped core. They are used for pipelines for various purposes, including those controlled by regulatory authorities (with the “P” index on the marking) at an operating pressure of up to 160 atm at temperatures from -70 to +450 °C.

Manufactured in accordance with GOST 17375-01 (type 3D with a bending radius of approximately 1.5 Du; executions 1 and 2) and in accordance with GOST 30753-01 (type 2D with a bending radius of approximately 1 Du; executions 1 and 2). Execution 1 is made on the basis of foreign standards (DIN) and is produced in Russia mainly with diameters from 21.3 mm to 48.3 mm. Version 2 is the most commonly used. Although all standard sizes are laid down in GOSTs, in Russia, according to GOST 17375-01, bends are made with a diameter of 32 mm to 426 mm. If you need a bend with a similar geometry with a diameter above 426, then usually (based on the operating conditions) stamp-welded bends (OKSH) or welded sectional bends (OSS) are used, and according to GOST 30753-01 - bends are made with a diameter of 530, 630, 720 and 820 mm. Also, curved bends are manufactured according to OST 34.10.699-97 (for thermal power plants and the nuclear industry from ferrous steels), according to OST 34.10.418-90 (for thermal power plants and the nuclear industry from stainless steels), as well as according to various specifications with geometry in accordance with GOST 17375 -01 stainless steel.

• Stamp-welded steeply curved are manufactured for main and field pipelines with diameters from 219 to 1420 mm for operating pressure up to 100 atmospheres for oil and gas industry facilities. Manufactured according to TU 102-488-95, bending radius - about 1.5 Du. There are also a number of other specifications.

• Welded sectional manufactured according to OST 34.10.752-97 (with a bending radius of 1 Du and 1.5 Du) from carbon and low alloy steels for heating networks and thermal power plants at an angle of 15, 30, 60 and 90 ° degrees for an operating pressure of up to 25 atm at an operating temperature up to 200 °C; according to various standard schemes (in particular, TS-583, developed on the basis of OST 34.10.752-97) with a diameter of 108 to 1620 mm; according to OST 36-21-77 with diameters from 500 to 1420 mm; according to OST 36-42-81 with diameters from 14 to 426 mm (with a bend radius of 1.5 Du) from carbon steels intended for the construction of pipelines designed for pressure up to 25 atm with a temperature range of −30 to +300 ° C at chemical enterprises , petrochemical, metallurgical, food, light and other industries. Also welded sectional bends can be manufactured according to TU 102-488-95, TU 51-29-81, OST 36-21-77, etc.

Varieties of bent branches

Bent bends are cold-bent, which are manufactured in accordance with GOST 24950-81 with a large (from 15 m) bending radius and hot-bent, which are manufactured according to TU 102-488-95, TU 102-488-05, TU 51-515-91 and other OST and specifications with bending radii from 1.5 to 6 Du.

see also

Links

Production of bends by cold bending

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