Influence of Parameter Deviations Vis-à-Vis Assignment Schedule on Thermally Stressed State of Main Thermal Power Plant Equipment

The current guidelines recommend evaluating the quality of start-up and shut-down modes, as well as operation modes under load, according to the compliance of start-up parameters with assignment schedules, standard instructions, performance charts, and reliability criteria and their limit values. The quality of maintaining operating modes is assessed via the permissible deviations of parameters from the values specified in standard instructions or assignment schedules. This study analyzes the approach and the permissible parameter deviations, according to which the start-up operations quality is assessed in terms of thermally stressed state of the critical elements of a thermal scheme. The analysis was performed on the basis of the thermally stressed state calculations of the T-125/150-7.7 turbine’s high-pressure rotor and the PGU-450 waste heat boiler’s high-pressure superheater outlet header with deviations of live steam temperature from the assignment schedule. Calculations were performed using the software package ANSYS. It is proposed to evaluate the quality of start-up modes on the basis of calculation of the cyclic strength of the power plant critical elements and not via deviation of the control parameter values without considering the specific time of their occurrence in relation to the assignment schedule, temperature state of element under consideration, and steam flow, among others.