The main causes for the quality decline of pipe bends and the methods for attention
The pipe bend is bent by a complete set of bending equipment,which is divided into two processes: cold bending and hot pushing.No matter what kind of equipment and pipelines,most of them use bends, mainly for oil, gas, infusion,engineering bridge construction,etc.
Analysis of the main causes for the quality decline of pipe bends and the methods for attention:
In pure bending, under the action of external force distance m, the tensile stress on the outer arm wall of the intermediate layer is reduced by the action of & 1,and the compressive stress on the inner side is reduced. The resultant force N1 and N2 make the cross section of the pipe change. Based on this factor,RX and SX are the main reasons for the decline of bend quality. Therefore,in gbj235-82,the RX value under various pressure levels and the thinning amount on the outside are clearly specified in order to control the RX and SX values and ensure the quality.
As mentioned in the previous article, when bending, the material is in tension at the outer side, and the position of the neutral axis in compression at the inner side is different from that of the bending method. The neutral axis is about 1 / 3 away from the outer wall when the top bending (compression bending) is working, and 2 / 3 away from the outer wall when the rotary bending (back bending) is working. Therefore, it is beneficial to use rotary bending method for thin-walled pipe bending.
The accuracy of the tube bending is also one of the factors that affect the quality of the tube bending. In addition to the specification and size required to be controlled within a certain tolerance range, we also require the user to select the corresponding bending tire according to the bending pipe diameter in use.
The bend ability and surface corrosion of pipes may also affect the quality of bends. During the field construction, the operator also needs to know the material, processing performance and production judgment of the surface corrosion of the processed pipeline.
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