Forecasting the Final Resource of the Metal Chimney Pipe of Non-Fronter Metallurgy

A comprehensive study of corrosion processes, damage and load-bearing capacity of a 45-m-high metal smoke pipe, which removes the gas-smoke mixture formed in the technological processes of non-ferrous metallurgy, was carried out, and a methodology for forecasting its final resource was developed. As a result of the analysis of the composition and temperature-moisture regime of the specified mixture, it was established that it is a gaseous medium aggressive to steel and causes corrosion of the pipe from the inside. As a result of the analysis of the results of the pipe wall thickness measurements, it was established that the corrosion rate was 0.12–0.26 mm/year, which corresponds to the medium aggressive degree of action of the gaseous medium on carbon steel.According to the intensity of corrosion, the pipe is divided into three conventional zones: the lower non-ventilated stagnation zone of corrosion of medium intensity below the chimney inlet; the average well-ventilated zone of less intense corrosion above the chimney inlet; the upper zone of condensate formation and the most intense corrosion. Analysis of the stress-strain state of the pipe taking into account corrosion damage showed that the most loaded dangerous zone of the structure is the place where the horizontal chimney cuts in, and the bearing capacity of the pipe is provided with a material utilization factor of 0.62–0.65. The limit values of the wall thickness and depth of corrosion damage in the cross-sections, which ensure the fulfillment of the conditions for the bearing capacity, have been determined. Based on the values of the corrosion rate, the time to reach the limit state was determined for all sections. In the lower, middle and upper zones of the pipes, the limit state will be reached after 18, 25 and 9 years, respectively, so without measures for repair and protection, the final resource of the pipe does not exceed 9 years. To increase the final service life of the pipe, it is recommended to replace the upper part of the pipe up to 18 years, and after 18 years - to protect the inner surface with heat-resistant organic silicon or epoxy enamel. Additional over 18 years of increase in ultimate life will equal the service life of the coating. Provided timely restoration of the anti-corrosion coating, the final resource of the pipe can be brought to the durability indicators of reinforced concrete and brick pipes of 70-80 years.