A boiler with the furnace outside the shell and brickwork around is described as which type?

• A. External furnace
• B. Internal furnace
• C. Container furnace
• D. Separate furnace

Answer: (A)

The key idea is where the furnace is located in relation to the boiler shell. When the combustion chamber is placed outside the boiler shell and is surrounded by brickwork, that setup is described as an external furnace. The brickwork acts as the firebox lining and insulation, keeping the high heat separate from the steel shell and helping to contain and manage the heat efficiently.

If the firebox were inside the boiler shell, the arrangement would be called an internal furnace, which changes how heat is transferred to the water and how the boiler is constructed. The other terms aren’t standard ways to describe this exterior-firebox design.