On-Line Control of Stresses in the Power Unit Pressure Elements Taking Account of Variable Heat Transfer Conditions

Coal-fired power units, now balancing shortages in the system, must be characterised by increasingly higher flexibility of operation. This means faster start-ups and capacity for frequent decreases increases output. These processes cause large temperature gradients elements unit turbine lead to an increase stress level. At such operating regime it is impossible ensure safety based on start-up characteristics only—it becomes necessary constantly monitor levels critical areas machinery equipment elements. The level can monitored on-line using algorithms Green’s functions Duhamel’s integral. paper presents examples modifications calculations valves casings during start-ups. By modifying basic algorithms, possible take into account impact variability heat transfer coefficients thermal Additionally, individual correction factors were determined specific stages Due modifications, obtain satisfactory agreement with results obtained from FEM-based entire heating process. Equations are also given that enable estimation values coefficient valves. proposed modification algorithm will substantially improve accuracy modelling transient states On-line monitoring operation facilitate operational control, ensuring at same time. calculated mode used estimate fatigue life consumption forecast residual lifetime components.