Steel shell and tube heat exchangers are widely used in chemical production. Whether it is fixed tube plate or floating tube tube plate, U-shaped shell-and-tube heat exchanger, the connection between tube and tube plate is an important structure in heat exchanger. And links. Since the heat exchange tube and the tube sheet are the only barrier between the tube side and the shell side of the heat exchanger, the good quality of the joint between the heat exchange tube and the tube sheet is the most important factor for the failure of the shell-and-tube heat exchanger. The joint type of the heat exchanger tube plate and the pipe is divided into expansion joint, welding, expansion joint and welding according to different use conditions of the heat exchanger.
First, put the expander into the tube, make the diameter of the tube become larger, plastically deform, and fit tightly on the tube sheet. The tube sheet that is in contact with the nozzle will become larger as the nozzle becomes larger, and elastic deformation occurs. When the expander is pulled out, the elastic deformation of the tube sheet will return to its previous size, but the nozzle after plastic deformation will remain large and will not return to its original shape, so that the two are tightly connected.
The quality of the bulge is mainly determined by the radial residual compressive stress on the pipe end. The value is the same as the material and size of the pipe and the tube plate, whether the groove is expanded, the tube expansion rate, the radial gap between the pipe and the tube sheet, the surface roughness, etc. Related factors. In order to obtain good and stable expansion performance, in addition to strict control of the processing accuracy of the tube sheet, to ensure the proper hardness difference between the tube sheet material and the tube material, it is necessary to correctly select the expander, tube expansion power and control means to ensure proper expansion. Degree and take a reasonable expansion sequence.
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