The most basic difference between elbows and bent pipes is that elbows are relatively shorter compared to bent pipes. R=1 to 2 times is an elbow, and any larger multiple is called a bent pipe. Cold bending pipes can be made using ready-made straight pipes and bending machines in the production process, and can be completed in one go without the need for secondary anti-corrosion treatment. But the elbow needs to be customized by the manufacturer, anti-corrosion treatment is required, and the ordering cycle is long. Elbows are more expensive than bent pipes, but their cost-effectiveness is much higher. It is well known that bent pipes without anti-corrosion treatment are prone to damage, but they are widely used in some projects with low requirements due to their low price.
The elbow needs to be customized by the manufacturer, with anti-corrosion requirements and a long ordering cycle. Cold bent pipes can be bent using existing straight pipes using a pipe bending machine. A one-time completion does not require secondary anti-corrosion treatment. There is a petroleum standard for the construction process of cold bending pipes, and an enterprise standard for the West East Gas Pipeline. But in open areas, elbows and bends can be used, considering only the cost. Elbows need to be hot bent, while bent ones can be cold bent, although the cost of elbows is high. Sometimes it is necessary to use elbows in narrow areas, such as in stone section pipe trenches, because the curvature radius of elbows is small, usually 6D, while that of elbows is 40D.