🔍 Key Concepts

• Location of gas flow path through the boiler (furnace → superheater → economizer → air heater → stack) • Function and typical position of an economizer vs an air heater in a marine boiler • What an overdeck superheater and steam soot blowers usually look like in sectional drawings

💭 Think About

• Trace the path of the hot gases from the furnace upward and toward the stack and note which heat‑recovery component is the last one before the gases exit • Compare the arrow "H" position to the tube banks marked elsewhere in the backpass and decide whether it is heating feedwater or incoming combustion air • Ask yourself which of the options would most likely be located in the gas outlet casing near the uptake, above the main generating bank

✅ Before You Answer

• Verify whether the tubes at arrow "H" are in the gas outlet path right before the stack opening • Check if any ducting for air or fans connects to the section indicated by "H" (this would favor an air heater) • Confirm that arrow "H" is not pointing at the drum, furnace wall tubes, or soot blower elements, but at a distinct tube bank in the upper rear gas path