A significant part of the life of structures at energy complex enterprises is affected by various external factors, which, in turn, alter the properties of the metal. The application of non-destructive testing methods enables the evaluation of the current condition of structural metals during operation, which helps prevent structural failure and extend service life through restorative measures. However, existing non-destructive testing methods do not provide comprehensive information on the strength and plasticity properties of metals, limiting the ability to accurately predict the lifespan of structures. The aim of this study is to assess the current state of metal structures using non-destructive testing methods to determine their strength capacities. This paper presents the results of examining metal structures of several long-serving objects. A non-destructive testing method was applied to determine the strength characteristics of the steels under study. For reliable results, statistical analysis methods were employed in processing the tensile strength values of the steels. The resulting dependencies indicate changes in the properties of structures in energy complex enterprises, underscoring the necessity for continued non-destructive monitoring and the substantial increase in information volume needed for further research.