Auxiliary boiler

An auxiliary boiler is an oil-fired marine boiler that raises steam when the ship’s main engine is stopped or at low load, where the exhaust-gas economizer cannot meet steam demand. It burns marine diesel oil or heavy fuel oil to supply steam for fuel and cargo heating, fuel-oil and lube-oil heaters, tank cleaning, accommodation services, and, on tankers, cargo discharge via steam-driven pumps. On motor ships it works in tandem with the exhaust-gas economizer, which recovers main-engine waste heat at sea, the auxiliary boiler covering port and maneuvering periods. Typical working pressures run 7 to 16 bar for general-service plants and higher on steam-heated tankers.