Serviceability restoration of operating fastening elements of the high pressure cylinder body of HPP steam turbines

Abstract

The mechanical characteristics of the fastening nuts steel of the high-pressure cylinder (HPC) of the steam turbine of the heat power plant (HPP), operating under the influence of hard temperature-power conditions for 21×10 4 hours, are outside the limits of the regulated values. It is the indicator of steel degradation. Using different types of heat treatment (HT), including recommended for 25Kh2M1F steel in the initial state, made it possible (in a certain extent of course) to restore the properties of the metal used for fastening fittings. The obtained results substantiate the efficiency of using of the HT for restoring the mechanical characteristics of steel for nuts of the HPC of the steam turbine in order to prolong their service lifetime.