The primary function of the vertical steel tanks — storage of oil and oil products transported through the trunk pipelines. Reliable and trouble-free operation of the tanks determines industrial safety of hazardous production facility, as well as the environmental safety of the territory adjacent to the facility.
Tanks sheet-by-sheet method is performed using mechanized welding technologies or manual electric arc welding with consumable electrode. However, the defects may occur in the welded joints. To identify the causes of their formation and assess the ability to take up the actual workloads, it is required to conduct comprehensive studies of the mechanical and metallurgical properties of both the base metal and the material in the zones of welded joints located near the defects.
The article presents the results of the analysis based on the scientific studies of the horizontal welds defects in the walls of the vertical steel tank made of steel 09G2S. Chemical compositions of sheet products metal and welded joints, macro- and microstructure of various zones of welded joints were studied; mechanical properties of the metal near the detected defects were analyzed. Theoretical calculations and experimental studies of the ability of welded joints of the tanks with defects to resist the effects of cyclic loads on the metal structure during operation were performed. Based on the results of the studies, the conclusions were drawn on the technical condition of the horizontal welded joints and sheet products of the tank, as well as on the causes of various defects formation (cracks, lack of penetration, non-fusion, slag inclusions). The actual ability of the welded joints to take up loads acting during tank operation was evaluated.
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