Question 710Steam Plants - Assistant Engineer

The correct answer is D) differential expansion can result from the temperature difference between the rotor and rotor casing. During a cold start-up, the temperature difference between the rotor and the rotor casing can be significant, leading to differential expansion. This differential expansion can cause stresses on the turbine components and increase the risk of damage. In contrast, during a hot shutdown, the temperatures are more uniform, and the risk of differential expansion is lower. The other options are incorrect because: A) Harmonic vibrations are more likely to occur during steady-state operation, not specifically during start-up. B) Blade erosion damage from dry steam impingement is a concern during both start-up and shutdown, not specifically during start-up. C) Lubricant film thickness is a concern during both start-up and shutdown, not specifically during start-up.