š Key Concepts
ā¢ Cold start-up vs. hot shutdown thermal conditions in a steam turbine
ā¢ How lubrication, vibration, steam quality, and thermal expansion each behave when machinery is cold
ā¢ Which condition creates the highest risk of physical damage to rotating and stationary parts
š Think About
ā¢ 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?
ā¢ Think about what happens to clearances between rotor and casing when metal is cold vs. when it is fully warmed up and expanded.
ā¢ Which of the listed problems would be most directly affected by a large temperature difference between different parts of the turbine?
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Before You Answer
ā¢ 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.
ā¢ 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?
ā¢ 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.