Monitoring the Percentage of Service Life Usage for Unheated High-Temperature Elements of Boilers

The use of monitoring systems for assessment of the condition of operating equipment at thermal power plants (TPPs) is demonstrated to still be urgent. The applicable management procedures and monitoring processes provided for assessment of service life characteristics of high-temperature elements of equipment are analyzed. The shortcomings of these approaches are highlighted, and the advantages of monitoring and predictive diagnostics processes for a meaningful assessment of the technical condition and control of the service life characteristics of critical units and elements of power equipment operating under creep conditions are substantiated. The object of examination is a once-through supercritical boiler. Outlet headers of the high-pressure convective superheater, steam collection chambers, and crossover pipelines between these headers and chambers are adopted as critical elements of this boiler. The design and construction materials of these elements, the scheme of the steam flow in these sections of the flowpath, and the diagram of the monitoring of the operating conditions in them have been studied. The methodological concepts are outlined of the developed monitoring system, including provisions for the procedure for recording and systematization of the readings of standard temperature and pressure transducers, approaches to calculation of characteristics from these data, which are necessary to assess the residual service life of elements. The algorithm of the system is prescribed in the form of a step-by-step execution of calculation procedures during monitoring within the scope of the proposed physical model of the metal service life’s expiry, which is based on regular relationships between the steam conditions and the operating time as well as on the properties of the metal. The stage of service life expiry is assessed by the principle of linear summation of accumulated damages. The specific is presented of the description in this algorithm of initially accumulated metal damages when a monitoring system is implemented in already operating equipment. Information is presented on a numerical check of the developed algorithm, including against actual data on the performance of the implemented monitoring system. Proposals are formulated on the procedure for assessing the condition of the metal within the scope of predictive diagnostics, carried out on the basis of the operating system.