Condition Monitoring of Heat Recovery Steam Boilers as a Basis for Elaborating Process Regulations for Their Operation

The article presents the results from analyzing the effectiveness of continuously monitoring the technical condition of combined-cycle power plant (CCPP) heat recovery steam generators (HRSG) with the aim of rendering aid to the thermal power plant personnel for correctly determining the main factors causing deviations or upsetting of HRSG operation modes and preventing the occurrence of equipment damages in the future. The technical condition of CCPP HRSGs is estimated on the basis of accumulated damage caused by deviation of their operation mode from the optimal one, which is quantitatively expressed in terms of accumulated equivalent operation hours. Examples showing the drain system performance on the damageability of HRSG parts are considered, especially with taking into account increased risk of damages to occur at the places in which the drain lines are welded to the steam lines and headers. The article shows the need for practical use of special maintenance programs of HRSG equipment, for which an analysis of accumulated operation hours or equivalent number of startups is proposed as a technical condition assessment criterion. Along with startup modes, the analysis takes into account the load variation modes within the load adjustment range that are accompanied by a change of steam parameters as well as off-design modes characterized by large disturbances of gas and steam temperatures, such as load shedding. The use of such programs will make it possible to reduce the costs of routine equipment maintenance works in the future and to timely detect equipment damages, thereby preventing the occurrence of emergency situations.