THE RESULTS OF THE METAL STUDY FOR CRITICAL TANKS AND THE ASSESSMENT OF THE DEFECTS FOUND

Abstract

The object of study was a reservoir for storing explosive substances (aviation fuel), which has been in operation for more than 35 years. The microstructure of low-carbon steel St3sp is a fine-crystalline two-phase system consisting of pearlite (a fine mechanical mixture of ferrite and cementite, dark inclusions) and ferrite, a light component. The distribution of ferrite and pearlite over the entire cross section is uniform. During non-destructive testing of the tank walls, it was revealed that there were delaminations on the bottom sheets. This defect can pose a significant threat to the safe operation of the container. Research has shown whether a tank with a defect is capable of maintaining operation, and whether operation is possible without repairs. As a result of the stress analysis of the model of the utor welded joint and the base metal of the tank without a defect in the form of delamination, it was found that the maximum stresses are concentrated near the weld and do not exceed the limit values for the material. Stress analysis of the model of the utor welded joint of a tank with a defect in the form of delaminations showed that the maximum stresses are concentrated not near the weld, but at the beginning of the defect and have large stress values, but, as in the model without a defect, do not exceed the limit values for material. In the studied samples, cracks do not develop, the defect in the form of delamination does not progress, rupture and bending occur under the same conditions and parameters as in samples without a defect. If the defect is located in a tank element, wall, within belts 1–4, it is necessary to carry out repairs to maintain conditions for safe operation.