Monitoring the Thermal Stress State in Steam Turbines

The principles of a program for monitoring stresses in rotors and bodies of stop and control valves of nonreheat steam turbines of up to 180 MW capacity to control the startup processes are formulated. The program based on the experimental data obtained by the VTI and ORGRES and calculated results obtained with the finite-element method is intended for microcomputers with hardware integrated into the electronics of the control system or the automatic process control system. Using the data from the regular control and measuring instruments, the program estimates the stresses in the “critical” elements of the steam turbine, compares them with the level permissible for the material, depending on the operating temperatures, service life, design and other parameters, and generates signals to adjust the startup process. The equivalent operating hours can also be calculated to assess the quality of startups and shutdown processes, accumulated damage, and relative past life. These data can be taken into account when deciding on maintenance operations. The algorithm of the stress monitoring system is implemented in the program limiting the rate of spinup and power change from the thermal stress state of the rotors of the high- and intermediate-pressure cylinders of the T-185/210 – 16.0 turbine.