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Upholding the corporate spirit of “Integrity, Harmony, Pragmatism, and Innovation,” we remain committed to a business philosophy that puts people first, embraces technological innovation, and emphasizes integrity and pragmatism.
Detailed introduction to the use of bends
Release time:
May 18,2022
A bend is formed using a set of specialized bending equipment, and the process can be categorized into two types: cold bending and hot push bending. Regardless of the type of machinery or piping involved, bends are widely used—primarily for transporting oil, gas, and liquids, as well as in engineering and bridge construction. During pure bending, under the influence of an external moment M, the outer wall of the neutral layer experiences tensile stress σ1, causing it to thin, while the inner wall experiences compressive stress, leading to thickening. The resultant forces N1 and N2 together cause changes in the cross-sectional shape of the pipe.
Bends are formed using specialized bending equipment and can be produced via two main processes: cold bending and hot push bending. Regardless of the type of machinery or piping involved, bends are widely used—primarily for transporting oil, gas, and liquids, as well as in engineering and bridge construction. During pure bending, under the action of an external moment M, the outer wall of the neutral layer experiences tensile stress σ1, causing it to thin, while the inner wall experiences compressive stress, leading to thickening. The resultant forces N1 and N2 together cause changes in the cross-sectional shape of the pipe.
Based on this factor, the primary reason for the decline in bend quality is the values of RX and SX. Therefore, clear specifications have been established for the RX values and the amount of wall thinning on the outer side under various pressure ratings. The purpose of these specifications is to control the values of RX and SX, thereby ensuring product quality. As mentioned earlier, during bending, the outer side of the material is subjected to tensile stress, while the inner side experiences compressive stress; the location of the neutral axis varies depending on the bending method.
During top-bending (compression-bending) operations, the neutral axis is located approximately one-third of the way from the outer wall; whereas during rotary bending (return-bending) operations, the neutral axis is located two-thirds of the way from the outer wall. Therefore, when bending thin-walled pipes, it is advantageous to use the rotary-bending method. The accuracy of the bending die is also one of the factors that influence the quality of the bent pipe. In the manufacture of bending dies, in addition to ensuring that standard dimensions are kept within specified tolerances, we also require users to select the appropriate bending die based on the diameter of the pipe being bent.
The flexibility of the pipe itself and its surface corrosion condition may also affect the quality of bent pipes. During on-site construction, operators must also be familiar with the material properties of the pipe being processed, its machinability, and the condition of surface corrosion to make informed judgments. We now provide a correlation chart showing the relationship between R (bending radius) and pipe outer diameter for users’ reference when selecting the appropriate combination of pipe diameter and wall thickness.
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