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The aim of the study described in this paper is to assess the effect of forces acting on the tube sheet during friction welding on the stress-strain state of the tube sheet.For this, we calculated the stresses and displacements arising in the tube sheet during friction welding. The calculations were carried out in the ANSYS (finite element analysis software package). To carry out the calculations, solid-state models of tube sheets with diameters of 400, 600, 800, 1000, 1200, 1400 mm and thicknesses of 30, 40, 50, 60, 70 mm were created. The diameter of the holes for the heat exchange tubes was chosen equal to 25 mm, the holes are placed on the vertices of an equilateral triangle with a step equal to 32 mm. Then, based on geometric models, grids of 8-node finite elements were created. The calculation model takes into account the symmetry of the geometric model and the character of loading relative to the YZ and XZ planes. The material used was steel with a Poisson's ratio of 0.3 and an elastic modulus of 2,11·105 MPa.As a result of the calculations, it was found that as a result of the action of force factors during friction welding, significant stresses and deformations arise in the tube sheet. The greatest values of deflection and stresses occur in the central sector of the tube sheet in the area of application of force. In this case, the zone of maximum stresses is significantly localized: they are concentrated around the central hole, and movements smoothly increase from the periphery to the center of the tube sheet.The value of this study is that it allowed to determine the need to use special equipment that increases the local stiffness of the tube sheet sector subjected to friction welding.

In order to increase corrosion resistance, different types of insulation of the inner surface of pipes are used, but corrosion in this case often occurs on the inner surface of pipes in the zone of annular welded joints, where there is no insulation. There is no doubt that protection of the internal weld joint is an urgent task, the purpose of which is to increase the reliability of pipeline transport systems. There is a problem of insulation of the area of welded joints of pipes. In areas of welded joints of pipelines, effective corrosion protection shall be provided. A variety of methods have been used to protect internal coated welded joints from corrosion. Protective bushings are the most common method of protection of welded joints of field pipelines with internal coating.

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