Fuel oil system
The fuel oil system for a diesel engine can be considered in two parts – the fuel supply and the fuel injection systems.
Fuel supply deals with the provision of fuel oil suitable for use by the injection system.
A slow-speed two-stroke diesel is usually arranged to operate continuously on heavy fuel and have available a diesel oil supply for manœuvring conditions.
In the system shown, the oil is stored in tanks in the double bottom from which it is pumped to a settling tank and heated.
After passing through centrifuges the cleaned, heated oil is pumped to a daily service tank. From the daily service tank the oil flows through a three-way valve to a mixing tank.
A flow meter is fitted into the system to indicate fuel consumption. Booster pumps are used to pump the oil through heaters and a viscosity regulator to the engine-driven fuel pumps. The fuel pumps will discharge high-pressure fuel to their respective injectors.
The viscosity regulator controls the fuel oil temperature in order to provide the correct viscosity for combustion. A pressure regulating valve ensures a constant-pressure supply to the engine-driven pumps, and a pre-warming bypass is used to heat up the fuel before starting the engine.
A diesel oil daily service tank may be installed and is connected to the system via a three-way valve. The engine can be started up and manœuvred on diesel oil or even a blend of diesel and heavy fuel oil.
The mixing tank is used to collect recirculated oil and also acts as a buffer or reserve tank as it will supply fuel when the daily service tank is empty.
The system includes various safety devices such as low-level alarms and remotely operated tank outlet valves which can be closed in the event of a fire.
