Under what circumstances are long-distance pipelines bent using thermal bending, and under what circumstances are they bent using cold bending? Are there standard regulations?
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Under what circumstances are long-distance pipelines bent using thermal bending, and under what circumstances are they bent using cold bending? Are there standard regulations? Are there big differences between them?
Cold-formed pipes feature fast forming speeds and high production volumes, without damaging the coating; they can be made in a variety of cross-sectional shapes to meet the requirements of different application conditions； Cold rolling can induce significant plastic deformation in bent pipes, thereby increasing their yield strength. However, cold-formed pipes also have some corresponding disadvantages; choose the processing method depending on the situation
The chemical composition and mechanical properties of the parent pipe used for hot bending of pipes have a significant direct impact on the hot bending process as well as the properties of the bent pipes. The chemical composition design, performance, and structural organization of the mother tube directly determine the quality and performance of heat-bent pipes. Both domestically and internationally, great emphasis is placed on the quality and performance of mother tubes used for heat-bent pipes, with clear requirements established in this regard. However, due to differences in the hot bending process, pipe bending production equipment, and control technologies, there are certain variations in the quality requirements for the parent pipes used in hot-bent pipes
For long-distance pipelines: elastic laying at 2–4°, cold bending at 5–14°, and hot bending at 15° or more
Cold bending can easily deform the pipes, resulting in ellipse and thinning levels that do not meet the standards； Hot bending is better, but sometimes heat treatment is required, especially for pipelines that are not carbon steel; this is done more often in such cases. Generally, after the bending of the pipe is completed, samples are taken for mechanical property analysis, right?
Which standard specification specifies this? ?
The angle of cold bending depends on the pipe diameter; the smaller the diameter, the greater the angle that can be achieved through cold bending. There are relevant papers available that provide methods for calculating this. Cold bending is carried out on-site according to requirements. Many construction units do not have pipe bending machines, and quality control for cold bending, especially at larger angles, is difficult to ensure effectively. Moreover, cold bending depends on the type of pipe being manufactured; in the case of spiral-welded steel pipes, it is necessary to convert them into seamless or straight-seam steel pipes, and this requires bending the entire pipe, which increases the complexity of construction. In projects where elbow pipes are used frequently, hot bending is employed in all cases, which may offer advantages in terms of quality control and construction convenience.
Pipelines should not have small diameters; cold bending is generally used for diameters of 200 mm or less. For larger diameters, hot bending is employed. Hot bending is not costly, and it ensures proper ellipticity as well as the desired hardness levels. The shaping is achieved through medium-frequency or high-frequency heating