🔍 Key Concepts

• Boiler and steam drum pressure changes when steam demand suddenly drops • Behavior of boiler water level (swell and shrink) with sudden load changes • Sequence of automatic boiler control actions: combustion control vs. safety valve lifting

💭 Think About

• When steam flow to the main engine is suddenly stopped, what is the immediate effect on steam pressure in the system? • Does a safety valve open before any control system can react, or does a control system usually act first to prevent overpressure? • How quickly does water swell or shrink in the boiler compared to the speed of pressure rise and burner control response?

✅ Before You Answer

• Compare time scale: which event happens in fractions of a second vs. several seconds • Decide whether safety valves are last‑resort devices or normal operating controls • Recall that combustion control reacts to steam pressure changes; does that reaction come before or after a safety valve would lift?