🔍 Key Concepts

• Trace the air heater symbol in the SG-0024 diagram and see which line provides its heat source when the plant is at sea under full power. • Look for steam lines labeled from the main boiler / turbines / feed system and see which one is connected to the air heater coils. • Distinguish between start‑up / low‑load sources of heat and normal full‑power underway operation in the diagram.

💭 Think About

• Follow the steam or gas flow path when both boilers and main turbines are operating—what energy stream is continuously available and economical to use for heating combustion air? • Compare where bleed steam, deaerating feed tank steam, and turbine exhaust appear on the diagram; which one is actually piped into the air heaters? • Ask yourself which source would give suitably high temperature but still be considered waste or recovery heat in a normal marine boiler plant.

✅ Before You Answer

• Verify which line actually enters the boiler air heater box in the illustration—do not assume from memory; trace the piping carefully. • Check the labels near the air heater connections for any reference to exhaust, bleed steam, or furnace gas to match them with the answer choices. • Confirm that the source you choose would be available only when underway at full power, not just during port, start‑up, or auxiliary steaming conditions.