🔍 Key Concepts
• Cold start-up vs. hot shutdown thermal conditions in a steam turbine
• How lubrication, vibration, steam quality, and thermal expansion each behave when machinery is cold
• Which condition creates the highest risk of physical damage to rotating and stationary parts
💭 Think About
• For each choice, ask: does this risk become worse when everything is cold and just starting to move, or when the unit is already hot and running down?
• Think about what happens to clearances between rotor and casing when metal is cold vs. when it is fully warmed up and expanded.
• Which of the listed problems would be most directly affected by a large temperature difference between different parts of the turbine?
✅ Before You Answer
• For each option, decide whether it is mainly a lubrication issue, vibration issue, steam quality issue, or thermal expansion issue, and then match that to cold start conditions.
• Ask yourself: during a proper start-up, is steam quality initially dry and erosive, or usually brought in gradually with warming lines and drains open?
• Consider which issue is specifically tied to different parts of the turbine heating up at different rates, and how that makes start-up more critical than shutdown.