The article is devoted to the development of a system for the technical diagnostics of slagging processes and contamination of the heating surfaces of coal-fired steam boilers, which operates online based on the interpretation of the standard information of ACS TP and scientifically proved algorithms for processing balanced equations to evaluate the thermal efficiency of radiation, semi-radiation and convective heating surfaces. The system is implemented at the level of algorithmic data and software in the programming language C #, which is built into the current system of the automatic control system of the boiler unit. The project aims to increase the reliability, efficiency and economy of steam boilers by quick maintenance of heating surfaces in an operational clean state, ensuring optimal performance characteristics of the main technological equipment. This system is at the trial operation stage at the BKZ-500-140 boiler unit, station No. 6 of JSC Krasnoyarsk CHP-2. The expected effect of the introduction of this boiler due to the reduction of the blowing cycles and the decrease in the slagging intensity will amount up to 2.175 million roubles annually per one boiler unit.