For the transportation of oil or gas, pre-bending of pipes is required. Without this procedure, the construction or industrial field of activity cannot do. To organize a strong turn, reliable connecting elements in the form of fittings are used in practice.
However, this technology is not suitable for every system and depends on the material. If you bend the pipe, you can maintain a decent appearance without violating the integrity of the structure.
Technology and Features
When creating any pipeline system, specialists select products from various metals. This is due to the fact that each has different technical characteristics. To change the shape of the structure, the action is carried out by means of radial and tangential forces. The former are necessary for the deformation of the section, and due to the latter, the formation of folds occurs. It is important that after the completion of all procedures, the radius remains the same, and there should be no corrugation inside the walls.
In the process of manufacturing metal structures using a solid material, an alternative option is used instead of welding — pipe bending. There are several main reasons for this choice:
- Material consumption is reduced due to the lack of cooking elements.
- Compared to systems where there are threaded or welded connections, in this case, the labor intensity indicator is much less.
- The hydroaerodynamics of the created passage improves.
- Compared to welding, there is no negative impact on the structure when bending pipes.
- Establish sealing and high reliability.
The choice of pipe bending method depends on several factors:
- The material from which the pipeline is made;
- Pipe thickness;
- What profile;
- Section, diameter and height;
- Radius of the bent surface;
- With what accuracy do you need to bend the pipes;
- What size of deformation is allowed in accordance with the standards established by GOST;
- How strong the structure remains at the bend points.
There are 4 main types of pipe bending:
- By means of portable pipe benders.
Each method has its own bending devices.
Use of hot bending
This method is relevant when a specialist does not have the necessary tools to use the cold method. This is a labor-intensive process, where preheating is carried out using special fillers. In this situation, the use of sifted river sand is relevant. It is important that it does not contain organic additives and crushed fractions. Otherwise, under the influence of high temperatures, the sand may burn to the walls of the structure. It is also important to avoid the ingress of wet raw materials, as this will create steam and increase pressure.
Bending of pipes with induction or hot heating should be carried out at a temperature regime within 900 degrees. It is important to ensure that there is no overburning, and also to use only one heating, otherwise the quality of the structure may deteriorate. As soon as all procedures are carried out, it is necessary to remove the sand and clean the cavities from residual contaminants. Stubs are also eliminated.
Features of cold bending
There are many advantages over hot bending. This method has a high productivity, which reduces the material costs of the implementation. Cold bending is optimally suited not only for black, but also for non-ferrous materials with high ductility. So, for example, it is possible to bend a pipe made of copper or aluminum into a spiral without exposure to high temperatures.
Bending has a negative effect on the quality and characteristics of the metal. As a result, the following defects appear, among which are:
- The wall thickness on the outside of the bend is reduced.
- Corrugation folds appear on the inside of the bend.
- The shape of the passage begins to change and takes on an oval appearance.
Deformations are most susceptible to structures made of soft metals with thin walls.
In order to properly organize the process and not cause mechanical damage, it is imperative to use a mechanical stabilizer, which is the mandrel. This is a special tool located in the cavity at the site of the future bend. The main goal is to prevent the occurrence of deformations. In practice, soft and hard structures are used.
A hard view assumes a guide view element. It is made from solid metal. The end face is rounded from the side of the working surface. Refueling is carried out from the bend point. The flexible structure is based on a special rod. At the end of one edge there are several segments of increased flexibility. Visually represented by hemispheres. Their use is necessary in order to avoid deformation of the passage.
As soon as the process comes to an end, it is pushed out of the fold, and special balls are located on the inner surface. The second version of the mandrel involves a number of difficulties in the process, so an automatic control system is used.
Based on the specific characteristics of the device, mandrels are used only in stationary mode. Their production is necessary for semi-automatic or automatic mode. To ensure uninterrupted control, a CNC system is used. With its help, monitoring of the implementation of all technological processes is carried out.
Operation of a portable pipe bender
If you need to bend pipes on site, the use of a portable tool is the best option. There are only a few types of tools:
- Lever. Due to the small shoulder, a small amount of physical effort will also be required. When using a metal structure (usually stainless steel up to ¾ inch), a bend of up to 180 degrees can be made.
- Crossbow. The structure should be located on two edges of the support, which rotate around their own axis. The shoe has a direct connection to the stem. There is pressure on the part of the pipe, which is located between the supports. Due to its low weight, it is possible to bend a pipe with a diameter within 100 mm at an angle of up to 90 degrees.
The rod creates pressure on the pipes. It can be hydraulic with manual or electric drive, mechanical screw.
- Electric. Pipe bending is carried out along the radius by means of replaceable segments. To bend the pipe at a certain angle, a swivel mandrel is used.
The tool has a number of positive qualities:
- The design is universal in use, since the kit provides for interchangeable segments;
- A 180 degree bend can be achieved;
- The work is automated, which reduces the cost of physical labor;
- There is a reverse stroke, the device can work in a smooth mode;
- There is no deformation, where the equipment and feed dynamics are coordinated;
- High level of performance.
If there is no mains power, you can use a replaceable battery and continue to operate the device.
It is considered the most common pipe bending method. A three-roller design with a roller pipe bender is used. A method is used that involves cold deformation of the metal. Alternative name — rolling. A distinctive feature is the fact that it can even be used to bend a titanium pipe. It is worth noting that it can be used in designs with any type of product: oval or round, it is able to quickly cope with a chrome pipe. Able to bend prepared elements with square, rectangular or triangular sections.
It is also allowed to bend pipes from any metal of large diameter. The universal property is provided by the work of rolling, which implies deformation in a certain direction. To ensure a certain type and size of the bend, a special caliber is selected.
A distinctive advantage of this type is the ability to bend pipes with a length of 5 m or more. In the construction industry, such manipulations are often required. The workpiece can be bent into an angle up to 360 degrees (into a ring). If it is supposed to work with pipes of large diameter, then all manipulations are performed using electric machines. The first end of the workpiece is installed in a special grip, then winding takes place with the required radius.
Machines allow you to create an accurate bending angle. The provision is carried out by classical mechanical work, or by setting certain tasks on the controller. It uses highly automated systems.
It will be extremely difficult to carry out such an operation with your own hands without proper practical skills. Therefore, it is recommended to entrust the work to professionals even when it is planned to bend the pipe. If errors are made in the calculations, there is a possibility of rapid deformation of the entire system, the occurrence of leaks and, in some cases, the creation of an emergency.